SISS-16 The Scientific International Symposium on SIMS and Related Techniques Based on Ion-Solid Interactions
Abstracts
June 19 - 20, 2014
Hokkaido University, Sapporo, Japan
http://siss-sims.com/siss/
i PROGRAM & CONTENTS
Program and Contents
June 19, 2014 (Thu) Opening remark (10:30-10:35)
Plenary (10:35-11:55)
O1-1. (10:35-11:15) - Tutorial talk - ………………………………………………………..
Computer Insight into Processes Stimulated by Cluster Projectile Impacts
Z. Postawa (Jagiellonian Univ.)
O1-2. (11:15-11.55) - Review talk - ………………………………………………………..
Light at the End of the Tunnel: Novel Approaches to Achieving Significantly Improved
Understanding of Secondary Ion Formation
K. Wittmaack (Helmholtz Zentrum Munchen)
Lunch (11:55-13:00)
Organic 1 (13:00-14:10)
O1-3. (13:00-13:30) - Invited - ……………………………………………………….……….
The evaluation of peptide structures using ToF-SIMS and data analysis
S. Aoyagi (Seikei Univ.)
O1-4. (13:30-13:50) …………………………………………………………….....……………….
Mass scale calibration with quaternary ammonium ions for TOF-SIMS spectra measured
by different TOF-SIMS instruments
S. Otomo (Furukawa Electric)
O1-5. (13:50-14:10) …………………………………………………………….....……………….
ToF-SIMS and PCA analysis of Oligomer distribution within Glass Fiber Reinforced
Plastic
Y. Kajiwara (Mitsubishi Gas Chemical)
Break (14:10-14:30)
Organic 2 (14:30-15:40)
O1-6. (14:30-15:00) - Invited - ………………………………………………………….…….
ToF SIMS as a navigation aid through the complex world of high throughput materials
discovery
M. Alexander (The Univ. of Nottingham)
O1-7. (15:00-15:20) …………………………………………………………….....………………
Measurements of secondary ions emitted from amino acid thin film with noble gases and
molecular cluster ion
K. Moritani (University of Hyogo)
O1-8. (15:20-15:40) …………………………………………………………….....………………
Possibilities and Limitations of Biological Analysis with novel Ar-GCIB SIMS Apparatus
1
2
3
5
7
9
10
12
ii PROGRAM & CONTENTS
M. Fujii (Kyoto Univ.)
Break (15:40-16:00)
Sponsored (16:00-17:20)
S1-1. (16:00-16:20) …………………………………………………...…………..………………. 14
Towards New Applications with CAMECA SIMS Instruments
M. Schuhmacher (CAMECA bu, AMETEK)
S1-2. (16:20-16:40) …………………………………………………...…………..………………. 15
Twenty-Five Years of Advances in TOF-SIMS Instrumentation and its Application
M. Terhost (ION-TOF)
S1-3. (16:40-17:00) …………………………………………………...…………..………………. 16
TOF-SIMS apparatus having function of Laser-SNMS for nano-scale mass imaging
T. Kashiwagi (TOYAMA)
S1-4. (17:00-17:20) …………………………………………………...…………..………………. 17
Recent progress of ion beam technologies in ULVAC-PHI
T. Miyayama (ULVAC-PHI)
Poster short presentation (17:20-18:00)
Poster session (18:00-19:00)
P-1. …………………………………………………………………………..……..………………. 18
Comparison of Measurement Repeatability among Beam position alignment, Z-direction
motion, and Auto-beam centering using a Cameca IMS 7f instrument
S. Miwa (CAMECA bu, AMETEC)
P-2. ……………………………………………………………………………..…..………………. 20
Reduction of phosphorus ion yield by electron beam irradiation under O2 primary ion
bombardment
Y. Hori (Toshiba Nanoanalysis)
P-3. ………………………………………………………………..………………..………………. 21
Deconvolution of Depth Profiles of GaN-Based Light Emitting Diodes with Tunnel
Junctions
Y. Nakata (Toray Research Center)
P-4. ………………………………………………………………..………………..………………. 23
Light element analysis in oxide and nitride materials
I. Sakaguchi (National Institute for Materials Science (NIMS))
iii PROGRAM & CONTENTS
P-5. ………………………………………………………………..………………..………………. 25
Q-SIMS analysis of impurities in SnO2 layer on glass substrate
T. Abe Sekine (ASAHI GLASS)
P-6. …………………………………………………………………………………..……..………. 27
Hydrogen isotope fractionation of water by diffusion in silica glass
M. Kuroda (Hokkaido Univ.)
P-7. …………………………………………………………………..……………..………………. 29
An investigation of depth resolution for dual-beam TOF-SIMS of Bi+ and lower energy Cs+
on depth profiling
J. Sameshima (Toray Research Center)
P-8. ……………………………………………………………………………..…..………………. 31
Helium depth profile of low energy 4He implanted samples
K. Bajo (Hokkaido Univ.)
P-9. …………………………………………………………………………………..………..……. 33
Organic Materials Analysis Using Different Primary Bi Ions in TOF-SIMS
R. Shishido (Tohoku Univ.)
P-10. ………………………………………………………………………………..…..…………. 35
Highly Sensitive Lipid Analysis and Imaging Mass Spectrometry with Cluster SIMS
Apparatus
M. Fujii (Kyoto Univ.)
P-11. …………………………………………………………………………………..…..…………. 37
Mass accuracy dependence on energy and extractor voltage of analyzer in TOF-SIMS
with single-stage reflection design
D. Kobayashi (Asahi Glass)
P-12. ………………………………………………………………………………..…..…………. 39
Atomic Level Analysis of Etched Carbon Fibers by the Scanning Atom Probe
M. Taniguchi (Kanazawa Institute of Technology)
P-13. …………………………………………………………………………………..…..…………. 41
Evaluation of Sample Shape after Evaporation in Laser Assisted Atom probe
M. Morita (The Univ. of Tokyo)
Social meeting (19:00-21:00)
iv PROGRAM & CONTENTS
June 20, 2014 (Fri) Instrumentation / Complementary 1 (9:00-10:10)
O2-1. (9:00-9:30) - Invited - ……………………………….………..………………….…..…. 43
Atom Probe Tomography: Successes and Challenges
T. F. Kelly (CAMECA)
O2-2. (9:30-9:50) …………………………………………..……………….……………………. 45
Dependence of Quantitativity on Dopant Distribution in Silicon Provided by Atom Probe
Tomography
T. Sasaki (Toshiba Nanoanalysis)
O2-3. (9:50-10:10) ………………………………………..……………….……………………. 47
Oxygen effect of Cr/Ni multilayered samples by resonance enhanced multiphoton
ionization sputtered neutral mass spectrometry
S. Nishinomiya (Nippon Steel & Sumitomo)
Break (10:10-10:25)
Instrumentation / Complementary 2 (10:25-11:55)
O2-4. (10:25-10:55) - Invited - …………………………….………..………………….…..…. 49
Laser desorption/ionization imaging mass spectrometry with ultra-high mass resolution
mass spectrometer.
T. Satoh (JEOL)
O2-5. (10:55-11:15) ………………………………………………………… ……..………….…. 51
Time-of-Flight Secondary Ion Mass Spectrometry using an ionic-liquid primary ion beam
generated by vacuum electrospray
Y. Fujiwara (National Institute of Advanced Industrial Science and Technology (AIST))
O2-6. (11:15-11:35) ………………………………………………………… ……..………….…. 53
In-situ GCIB Cross-section Imaging of Organic Materials
-Toward the Determination of Accurate Depth Distributions-
S. Iida (ULVAC-PHI)
O2-7. (11:35-11:55) ………………………………………………………… ……..………….…. 55
SIMS Depth Profiling by FIB Crater Wall Imaging of Organic and Inorganic Surfaces
D. Rading (ION-TOF)
Lunch (11:55-13:00)
v PROGRAM & CONTENTS
Inorganic (13:00-14:40)
O2-8. (13:00-13:30) - Invited - …………………………………………….…….……………. 57
Light Elements and Related Materials Properties Revealed by TOF-SIMS
L. Zhang (Institute of Metal Research, Chinese Academy of Science (CAS))
O2-9. (13:30-14:00) - Invited - ………………………….………….…………………………. 59
From crater to crater: application of high resolution SIMS to Geosciences
K. Yi (Korea Basic Science Institute)
O2-10. (14:00-14:20) …………………………..……………………………..…..………………. 60
Development of high-precision analysis of multilayer structure
T. Shiramizu (Mitsubishi Electric)
Break (14:20-14:40)
Biomedical / Imaging (14:40-16:10)
O2-11. (14:40-15:10) - Invited - ………………………………….………..…………………. 62
Visualizing accumulation of photosynthetic products in plant using isotopic labeling and
SIMS
M. Takeuchi (The Univ. of Tokyo)
O2-12. (15:10-15:30) …………………………..……………………………..…..………………. 64
Localization of 15N-minodronate by Isotope Microscopy and Histochemical Assessment
for the Biological Effects of Minodronate to Bone Cells in Mice
N. Amizuka (Hokkaido Univ.)
O2-13. (15:30-15:50) …………………………..……………………………..…..………………. 66
Molecular Analysis of Biological Tissues using Time-of-Flight Secondary Ion Mass
Spectrometry (TOF-SIMS) and Gas Cluster Ion Beam (GCIB) sputtering
I. Ishizaki (ULVAC-PHI)
O2-14. (15:50-16:10) …………………………..……………………………..…..………………. 68
High Resolution Imaging Mass with Focused Ar Cluster Beam
J. Matsuo (Kyoto Univ.)
Closing remark (16:10)
Computer Insight into Processes Stimulated by Cluster Projectile Impacts
Z. Postawa Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Kraków, Poland
Since the dawn of computer technology, computer simulations have established themselves as an important theoretical partner to experimental measurements. If a new phenomenon is observed one is usually trying to find general trends that may occur in the data by systematically modifying the initial parameters of the probed system. This task can be accomplished both by experimental measurements and computer modeling. Actually, a successful comparison of the experimental and theoretical observations is usually an important step in establishing credentials of the computer model. In the next step, one usually wants to understand which processes are responsible for these trends to occur. Computer simulations are particularly well suited to pursue this goal as they enable one to visually inspect the atomic motions giving rise to any particular event or sets of events.
A theoretical insight into processes taking place during cluster bombardment events on metal and organic samples will be presented. Molecular dynamics computer simulations are used to probe energy deposition pathways, damage buildup, ejection mechanisms and evolution of the surface morphology stimulated by an impact of cluster projectiles that are currently used in secondary ion and neutral mass spectrometry (SIMS/SNMS) experiments. The effect of the projectile size, incident energies and angles is investigated within the range employed during SIMS experiments. A special emphasis is placed on probing the processes that determine the depth resolution in depth profiling experiments performed by SIMS/SNMS. Recent developments and challenges in computer modeling of cluster bombardment of organic materials will be discussed.
1
Light at the End of the Tunnel: Novel Approaches to Achieving Significantly Improved Understanding of Secondary Ion Formation
Klaus Wittmaack Helmholtz Zentrum München, ISS, 85758 Neuherberg, Germany
For more than 30 years, attempts have been made to describe secondary ion yields on the basis of the so-called tunneling model. Unfortunately, the model has been considered to apply even when it should have been clear that the experimental data under consideration did not comply with the most essential prediction: the ionization probability should increase strongly with the inverse velocity of the sputtered atom. A comprehensive evaluation [1] has shown that in reliable sets of experimental data a velocity dependence cannot be identified. The study [1] also addressed the question whether available SIMS instruments, home-made or of commercial design, are capable of providing the desired spectral information. In order to arrive at an answer, it is necessary to examine the relevant performance issues very carefully. Such an elaborate exercise [2] has led to the remarkable conclusion that, at least in the exemplary case studied [3], secondary ions and sputtered neutral atoms do not exhibit the same surface binding energy. Hence the common approach of describing secondary ion energy spectra as the product of the neutral spectrum and a (velocity dependent) ionization probability has no basis. Exciting progress was also made in the field of quantitative analysis. Considering negative secondary ion yields previously determined for a large variety of dopants implanted in silicon and measured under Cs bombardment [4], it was found that the data can be described very well if they are presented as a function of the sum of the electron affinity and the electronegativity of the sputtered atom [5]. This lecture describes recent progress with the aim of showing that the field is now ready for new attempts to make SIMS a quantitative surface analytical tool. [1] K. Wittmaack, Surf. Sci. Rep. 68 (2013) 108. [2] K. Wittmaack, Int. J. Mass Spectrom. 359 (2014) 55. [3] K. Wittmaack, H. Gnaser, Int. J. Mass Spectrom. 358 (2014) 49. [4] R.G. Wilson, Int. J. Mass Spectrom. 143 (1995) 43. [5] K. Wittmaack, Anal. Chem. (2014) http://dx.doi.org/10.1021/ac501006g.
2
The evaluation of peptide structures using ToF-SIMS and data analysis
Satoka Aoyagi 1
1 Department of Material and Life Science, Seikei University, 3-3-1 Kichijoji-kitamachi, Musashino,
Tokyo, 180-8633, Japan
1. Introduction
Peptides are crucial for understanding biological phenomena and often essential for
developing novel medicines. For studying peptides, it is important to analyse peptide structures in
detail. Peptide analysis systems were developed mainly based on chromatography and mass
spectrometry which are not applicable to one monolayer of a peptide on biochip or bio-device surfaces.
On the contrary, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is applicable to analyse
small quantities of sample materials and surface structures and requires no pre-treatments and
therefore it is potentially a promising tool for analysing biochips. However, in terms of peptide or
protein analysis using ToF-SIMS, mainly amino acid fragment ions [1] are detected although some of
ToF-SIMS techniques using massive cluster ion sources also provide large fragment ions indicating
amino acid sequences.
In general, ToF-SIMS is useful for evaluating complex samples such as proteins and peptides
because it provides detailed chemical information from the most upper surface of large molecules and
chemical mappings with high spatial resolution approximately 100 nm. It is, however, often difficult
to interpret ToF-SIMS spectra of complicated samples such as intelligent materials and biological
samples due to intricate fragment ions and overlapped peaks. Recently multivariate analysis
techniques, such as principal component analysis [1] and multivariate curve resolution (MCR) [2],
successfully applied into a variety of scientific fields have been also introduced into ToF-SIMS data.
Moreover, gentle-SIMS (G-SIMS) [3], developed for analyzing static-SIMS spectra in terms of the
degree of fragmentation, has recently been applied to various samples [4,5] in order to separate
secondary ions related to target molecules from others.
In this study, mainly there analysis studies are described: They are the identification of
unknown peptide using G-SIMS [6] and peptide structural analysis using massive cluster ions in terms
of the amino acid sequence [7] and evaluation of peptide structures depending on the interaction with
lipid membranes.
Figure 1 The concept of peptide analysis using ToF-SIMS.
2. Methods and Materials
The identification of unknown peptide using G-SIMS
(Des-tyr)-leu-enkephalin and (des-tyr)-met-enkephalin were dissolved in pure water
(0.01g/50ml), respectively, and also 0.01g of chicken egg white lysozyme (Sigma-Aldrich Co., St
Louis, MO, USA) was dissolved in 100ml of pure water. Next, 20 µl of each solution was dropped on
the cleaned ITO substrate.
3
Positive ion spectra were obtained with TOF-SIMS 5 (ION-TOF GmbH, Münster) with 25
keV Mn+ (0.1pA), Bi
+(0.5pA), Bi3
+ (0.1pA) primary ion sources, respectively, on the same area of
each sample. All measurements at the same area of each sample were acquired while maintaining the
total primary ion dose at less than 1012
ions/cm2 to ensure static conditions. The ion dose of each
measurement for the same sample was the same.
Peptide structural analysis using massive cluster ions in terms of the amino acid sequence
Model peptides were [Val5] angiotensin I bovine (M.W. 1281.7, Sigma-Aldrich), angiotensin
II human (M.W. 1045.5, Sigma-Aldrich), (dey-Tyr)-Met-enkephalin (n-GGFM-c, M.W. 410.2,
Bachem AG, Switzerland), (dey-Tyr)-Leu-enkephalin (n-GGFL-c, M.W. 392.2, Bachem).
Positive ion spectra of each peptide sample were acquired with a TOF-SIMS J105 (Ionoptika
Ltd., UK) using an Ar2000+ primary ion at 20 keV. The TOF-SIMS J105 uses a continuous primary ion
beam to generate a stream of secondary ions that are then sampled by a buncher that produces a tight
packet of ions at the entrance to a harmonic field reflectron and an Ar cluster ion source has been
introduced to the system. The system was described in detail elsewhere [3, 4].
The evaluation of peptide structures depending on the interaction with lipid membranes
Amyloid beta (1-40) samples on different lipid membranes (DPPC and DOPC) on gold
substrates were prepared. And, positive ion spectra were obtained with TOF-SIMS 5.
3. Results and Discussion
G-SIMS and g-ogram simplified the complicated ToF-SIMS spectra of peptide samples and
indicated the molecular ions though they were not main peaks in the ToF-SIMS spectra.
Figure 2 G-SIMS spectra of the peptide. Figure 3 The peptide sample g-ogram
Ar cluster ions provide spectra similar to those obtained with low-energy CID which indicate
the amino acid sequences of the peptides.
It is suggested that amyloid beta (1-40) has different aggregation styles depending on the lipid
membrane.
4. Conclusions
Data analysis for ToF-SIMS image and spectrum data is useful for extracting pure or simpler
components from complicated samples. PCA is useful for understanding outlines of samples. On the
other hand, MCR is useful for obtaining spectrum and image information of samples directly. In
addition, G-SIMS & g-ogram are useful for obtaining important information form secondary ions.
Huge cluster ion sources such as Ar cluster sources are crucial for evaluating peptide
structures.
References
[2] J.L.S. Lee, I.S. Gilmore, I.W. Fletcher, M.P. Seah. Surf. Interface Anal. 41, 653 (2009).
[1] M.S. Wagner, D.G. Castner. Langmuir 17, 4649 (2001).
[3] I.S. Gilmore, M.P. Seah. Appl. Surf. Sci. 161, 465 (2000).
[4] S. Aoyagi, I. S. Gilmore, I. Mihara, M. P. Seah, I. W. Fletcher, Rapid Commun. Mass. Spectrom.
26, 2815 (2012).
[5] I. Mihara, K. Nakagawa, M. Kudo, S. Aoyagi, Surf. Interface Anal. 45, 453 (2013).
[6] S. Aoyagi, I. Mihara, M. Kudo, Surf. Interface Anal., 45(1), 190 (2013).
[7] S. Aoyagi, J. S. Fletcher, S. Sheraz (Rabbani), T. Kawashima, I. Berrueta Razo, A. Henderson, N.
P. Lockyer, and J. C. Vickerman, Anal. Bioanal. Chem., 405(21), 6621 (2013).
4
Mass scale calibration with quaternary ammonium ions for TOF-SIMS spectra measured by different TOF-SIMS instruments
S. Otomo1, and D. Kobayashi2
1 Yokohama R&D Laboratories, Furukawa Electric Co. Ltd., 2-4-3 Okano, Nishi-ku, Yokohama, 220-0073 Japan;
2Reasearch Center, Asahi Glass Co. Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama 221-8755 Japan
[email protected] 1. Introduction
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has recently become an increasingly useful surface analysis technique for the characterization, understanding and optimized control of molecular, organic and polymer surfaces in industrial field. An accurate calibration of the mass scale is an essentially important step for the assignment of a reliable chemical composition to particular and unknown ion peaks as well as for the identification of surface chemical species. Some pioneering works on the standardization of the mass scale calibration in static SIMS have been reported by the National Physical Laboratory (NPL) [1-3]. Based on these previous reports, ISO 13084 was formulated in 2011 in terms of a procedure for the mass scale calibration.
A mass scale of a TOF-SIMS spectrum is often calibrated by extrapolation of several identified secondary ions with low mass number such as hydrocarbon fragmentation ions. However, it is difficult to assign a reliable chemical composition to unknown ion peaks which are located in high mass region of TOF-SIMS spectrum using a conventional extrapolation method. Therefore, for accurate mass calibration of large molecules of mass m, ISO 13084 highly recommends analysts to include an ion with a mass of 0.55m or over among the ions selected for the mass scale calibration. However, TOF-SIMS spectra have often no correctly identified ions containing a mass larger than 55% of the peak to be assigned.
A novel mass calibration method with internal additives has been discussed to improve the mass accuracy of high-mass ion [4,5]. The new method with internal additives has advantages that non-degraded ions are available and interpolation is possible. Positive molecular ions of quaternary ammonium salts can be detected with high sensitivity and are assumed to become suitable internal additives. As already reported in our previous study [5,6], the mass scale calibration with three molecular ions of the ammonium salts showed the good mass accuracy of high-mass molecular ions for one TOF-SIMS instrument (TOF.SIMS 5, Bi3++ primary ions).
In this presentation, to confirm the effectiveness of this new mass calibration method with the molecular ions of the ammonium salts, the mass accuracy of high-mass molecular ions was investigated for other TOF-SIMS instruments. 2. Experimental
Tinuvin 770 was used as a target sample in this study. Approximately a 10 mg granule of Tinuvin 770 was dissolved into 1 ml of acetone and was coated on a Si wafer by a spin-coater. Five kinds of alkyl quaternary ammonium salts with different molecular weights were prepared as internal additives for the novel mass calibration method: octyltrimethylammonium bromide (C8TMA), tetradecyltrimethylammonium chloride (C14TMA), octadecytrimethylammonium chloride (C18TMA), cetylpyridinium chloride (CPC) and benzyldimethyltetradecylammonium chloride (Bzl). These five quaternary ammonium salts were diluted with 10 ml of distilled water and 20 µl of conc-NH3 to approximately 1 mmol/l, respectively [4-6]. Several drops of the mixed solution added to Tinuvin 770 coated on a Si wafer by a dropper.
The samples were measured by two TOF-SIMS systems (TRIFT-IV with Au+ primary ions and TOF.SIMS 5 with Bi3++ primary ions). 3. Results and Discussion
Figure 1 shows typical positive TOF-SIMS spectrum of Tinuvin 770 coated on Si wafer with internal additives using the TRIFT-IV. Molecular ion derived from Tinuvin 770 was detected as ion of
5
the addition of hydrogen, which is C28H53N2O4+. The molecular ions of quaternary ammonium salts were also detected: C11H26N+ derived from C8TMA, C17H38N+ derived from C14TMA, C21H38N+ derived from CPC, C21H46N+ derived from C18TMA, and C23H42N+ derived from Bzl. C8TMA, C14TMA and C18TMA are alkali quaternary ammonium salts and have similar chemical structure. Thus, molecular ions of these quaternary ammonium salts were selected for mass scale calibration.
After the mass scale calibration using molecular ions of C8TMA, C14TMA and C18TMA, relative mass accuracy, W, across the mass scale for TOF-SIMS spectra using TRIFT-IV (Au+) and TOF.SIMS 5 (Bi3++) were compared, as shown in Fig. 2. Along the lines of ISO 13084, the mass accuracy, ∆M, is defined as the difference between the measured peak mass, Mp, and the true mass, MT, given by ∆M = Mp－MT. In this study, the calculated exact mass is treated as true mass. The relative mass accuracy, W, is given by W =∆M / MT.
For both spectra, W of the CxHy fragment ions indicated negative, and the different range of the scatter of W showed. These results show that the conventional mass scale calibration with frequently employed CXHY fragment ions leads to the poor value and the large scatter in the mass accuracy of molecular ions. The relative mass accuracy of C28H53N2O4+ of Tinuvin 770 indicates good value and approximately 10 ppm. The novel method with internal additives is more effective to improve the mass accuracy of high-mass ions than the conventional one. Quaternary ammonium salts are potential candidates of internal additives.
TRIFT-IV
Au+(30 kV)200×200 µm2
124
58
140
0 100 200 300 400
Inte
nsity
(ar
b. u
nits
)
m/z500
C3H8N+
C8H14N+
C9H18N+172
×5
256
312
332
C11H26N+
(C8TMA)C14H38N+
(C14TMA)
C21H46N+
(C18TMA)
C23H42N+
(Bzl)304
C21H46N+
(CPC)
481
C28H53N2O4+
(Tinuvin770)
Figure 1. Positive TOF-SIMS spectrum of five kinds of alkyl quaternary ammonium salts on the Tinuvin 770 coated Si wafer.
0 100 200 300 400
m/z500
0
100
-100
-200
-300
-400
W ,
ppm
0 100 200 300 400
m/z500
0
100
-100
-200
-300
-400
W ,
ppm
CXHY fragment ions
CXHY fragment ions
C8TMA C14TMAC18TMA
CPC
Bzl C28H53N2O4+
(Tinuvin770)
C8TMA C14TMA C18TMA
CPC Bzl C28H53N2O4+
(Tinuvin770)
(a) TRIFT-IV(Au+) (b) TOF.SIMS 5 (Bi3++)
Figure 2. Relative mass accuracy, W, across the mass scale for two TOF-SIMS spectra after mass scale calibration using alkyl quaternary ammonium ions; C8TMA, C14TMA and C18TMA. References [1] I. S. Gilmore, F. M. Green and M. P. Seah, Surf. Interface Anal. 39, (2007), 817. [2] F. M. Green, I. S. Gilmore and M. P. Seah, J. Am. Soc. Mass Spectrom. 17, (2006), 514. [3] F. M. Green, I. S. Gilmore, J. L. S. Lee, S. J. Spencer and M. P. Seah, Surf. Interface Anal. 42, (2010), 129. [4] D. Kobayashi, S. Aoyagi, S. Otomo and H. Itoh, The Scientific International Symposium on SIMS and Related Techniques Based on Ion-Solid Interactions(SISS-15) (2013) 37. [5] D. Kobayashi, S. Otomo and H. Itoh, J. Surf. Anal. 20, (2014), 187. [6] D. Kobayashi, S. Aoyagi, S. Otomo and H. Itoh, 19th International Conference on Secondary Ion Mass Spectrometry(SIMS-19) (2013) 358.
6
ToF-SIMS and PCA analysis of Oligomer distribution within Glass Fiber Reinforced Plastic
Y. Kajiwara1, 2, H. Nagashima3, S. Nagai3 and S. Aoyagi2
1MGC chemical analysis center, Mitsubishi Gas Chemical Company, INC., 6-1-1 Niijuku, Katsushika, Tokyo 125-8601 Japan
2Graduate School of Science and Technology, Seikei University, 3-3-1 Kichijoji-Kitamachi, Musashino, Tokyo 180-8633 Japan
3Technology Department, Mitsubishi Engineering-Plastics Corporation, 5-6-2 Higashiyawata, Hiratsuka, Kanagawa 254-0016 Japan
[email protected] 1. Introduction
Polycarbonate (PC) has been widely utilized for manufacturing a variety of industrial products such as precision and clinical instruments owing to its optical and mechanical properties. For reinforcing its strength and toughness, glass fiber is generally added to the polymer, which is known as glass fiber reinforced plastic (GFRP). However, its surface appearance becomes rough because of the exposed glass fibers on the surface. For preventing such defect of mold specimen surface, PC oligomer is deliberately added to glass fiber reinforced PC because PC oligomer migrates to the surface during injection molding and blocks the exposure of glass fiber on the surface [1]. On the other hand, mechanical behavior of GFRP is highly dependent on the interphase of glass fiber and polymer matrix [2]. Based on the atomic force microscope (AFM) investigation of glass fiber reinforced polypropylene (PP) composites, it is believed that the deformation of PP having low molecular weight occur in the interphase of glass fiber whose thickness is from less than 100 nm to around 300 nm [2]. However, the distribution of low molecular weight component in the interphase has not been directly investigated based on their chemical properties because of the limitation of analysis methods for acquiring chemical information on such a small scale.
ToF-SIMS has been widely used for studying surface and interphase chemistry because ToF-SIMS provides detailed chemical information with high spatial resolution down to a few hundred nanometers and high surface sensitivity at the ppm level. However, the complexity of mass spectra is one of the barriers for characterization using ToF-SIMS. To interpret complex mass spectra, multivariate analysis (MVA) methods such as principal component analysis (PCA) have been applied to ToF-SIMS data [3, 4]. PCA is used for reducing the number of variables with minimal loss of information and differentiating the characteristic features within the ToF-SIMS spectra.
In this study, PCA was applied to the ToF-SIMS spectra in order to find indicative secondary ions for PC oligomer and then the distribution of PC oligomer within the glass fiber reinforced PC was investigated. 2. Experimental Sample preparation
The two types of composites were prepared by injection molding. One was the composites consisting of PC polymer (Mv 21,000, Tg 149 C-deg: Mitsubishi Engineering-Plastics Co., Tokyo, Japan) and PC oligomer (Mv 5,100, Tg 104 C-deg: Mitsubishi Engineering-Plastics Co., Tokyo, Japan) in weight ratios of 100:0, 90:10 and 70:30 and the other was the composites consisting of PC polymer, PC oligomer and glass fiber (Nippon Electric Glass Co., Ltd., Otsu, Japan) in weight ratios of 90:0:10, 80:10:10 and 60:30:10. ToF-SIMS measurement
Positive ion ToF-SIMS spectra were obtained using TRIFTⅡ (Physical Electronics, Inc., Chigasaki, Japan) with a Ga+ primary ion beam accelerated at 15 kV (1.4 nA) in bunched mode. A primary ion beam was rastered over an area of 100 µm by 100 µm with a pulsed low-energy electron flood gun. Multivariate analysis
PCA was performed using PLS Toolbox (Eigenvector Research, Inc., Wenatchee, WA) for Matlab (The MathWorks, Inc., Natick, MA). Intensities of secondary ions in the mass ranges from 0 to
7
400 u were compiled manually to create a peak list (240 peaks) where impurities such as Na, Mg, Si, K, Ca and Ga were eliminated. 3. Results and Discussion
PCA was performed on the spectrum dataset of the composites consisting of PC polymer and PC oligomer to find indicative secondary ions for PC oligomer. Six spectrum data were obtained from the surface of each sample. The dataset were normalized to the total intensity and mean-centered before PCA.
The score on PC4 gradually increased along with the concentration of PC oligomer, and it was clearly shown that C8H5O3 (m/z 149.02 u) was one of the dominant secondary ions in the positive loadings on PC4. The intensity of C8H5O3 normalized to the total intensity also gradually increased along with the concentration of PC oligomer even in the raw spectrum data (Fig. 1). Therefore, C8H5O3 is considered to be an indicative secondary ion for PC oligomer.
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0 5 10 15 20 25 30 35
No
rmal
ized
co
un
ts
Weight ratio of PC oligomer (wt%) Figure 1. The normalized intensities of C8H5O3 in the raw spectrum data. The weight ratios of PC polymer to PC oligomer are 100:0, 90:10 and 70:30. Then, the spectrum image data of cross-section surface of the composites consisting of PC
polymer, PC oligomer and glass fiber were used to investigate the PC oligomer distribution. Based on the observation of C8H5O3 images over the cross-section surfaces, the distribution of
C8H5O3 was concentrated around the glass fiber in the composites including PC oligomer. This result indicates that PC oligomer is localized in the interphase of glass fiber and PC polymer. 4. Conclusion
In conclusion, an indicative secondary ion for PC oligomer revealed by PCA suggests that PC oligomer is localized in the interphase of glass fiber and PC polymer. This chemical information is consistent with physical properties such as the glass transition temperature and the viscoelasticity. Therefore, it is suggested that a combination of ToF-SIMS and PCA provides useful information for understanding chemistry of high functional materials such as inorganic and organic composite materials. References
[1] T. Umemura, N. Ogawa, K. Ando, M. Kusakabe, Seikei-Kakou, 1995; 7 (4), 210-215. [2] S.-L. Gao, E. Mäder, Composites: Part A, 2002; 33, 559-576. [3] M. S. Wagner, D. J. Graham, B. D. Ratner and D. G. Castner, Surf. Sci., 2004; 570, 78-97. [4] B. J. Tyler, Appl. Surface Sci., 2006; 252, 6875-6882.
8
ToF SIMS as a navigation aid through the complex world of high throughput materials discovery
Morgan R Alexander
Laboratory of Biophysics and Surface Analysis, School of Pharmacy, The University of Nottingham, Nottingham, NG7 2RD, UK
[email protected] The materials discovery approach offers the opportunity to identify polymers from a wide chemical combinatorial space using micro arrays on which parallel screens of cell response is undertaken. [1] ToF SIMS has proven very useful as a navigation aid through the large number of different materials and the complex interface between them and the biological world.[3] This methodology has led to the discovery of a new class of polymers resistant to bacterial attachment using the process exemplified in Figure 1 where ToF SIMS sits in the feedback loop of box d.[4] Success in the discovery of materials which support pluripotent stem cell expansion has been facilitated by this approach.[5] This presentation will dissect this process and discuss the pivotal role for SIMS as this methodology progresses to contribute to our understanding of the materials genome.
References [1] Celiz A, Smith J, Langer R, Anderson D, Barrett D, Young L, Denning C, Davies M & Alexander
M. Materials for stem cell factories of the future. Nature Materials 13, 570-579 (2014). [2] Hook A, Anderson D, Langer R, Williams P, Davies M & Alexander M High throughput methods
applied in biomaterial development and discovery. Biomaterials 31, 187-198 (2010). [3] Hook A, Chang C, Yang J, Luckett J, Cockrayne A, Atkinson S, Mei Y, Bayston R, Irvine D,
Langer R., Anderson D, Williams P, Davies M & Alexander M. Combinatorial discovery of polymers resistant to bacterial attachment Nature Biotechnology 30, 868-875, (2012).
[4] Mei Y, Saha K, Bogatyrev S, Yang J, Hook A, Kalcioglu I, Cho S, Mitalipova M, Pyzocha N, Rojas F, Vliet K, Davies M, Alexander M, Langer R, Jaenisch R & Anderson D. Combinatorial Development of Biomaterials for Clonal Growth of Human Pluripotent Stem Cells. Nature Materials 9, 768-778 (2010).
9
Measurements of secondary ions emitted from amino acid thin film with noble gases and molecular cluster ion
K. Moritani1, I. Ihara1, S. Nagata1, N. Inui1 and K. Mochiji1
1 Graduate School of Engineering, University of Hyogo, 2176 Shosha, Himeji, Hyogo 671-2201 Japan;
[email protected] 1. Introduction
Large gas cluster ion projectiles have improved the problem of molecular fragmentation and enhanced the emission of the molecular ion. [1,2] Because of the low energy per constituent of gas cluster projectiles in the range of several eV, the fragmentation of organic molecules can be substantially suppressed, causing the increase of the molecular ion yields in the ToF-SIMS. In order to apply this technique to the analysis of macromolecules in the practical bio-samples, however, the signal intensity of high mass molecular ions should be more enhanced. The secondary ion intensity, when excluding analyzer related factors, can be determined from sputtering yield and ionization probability. Sputtering yield can increase with increasing incident ion energy, which must trade off against molecular fragmentation. [2]
The ionization probability is influenced by the properties of the bombarding primary ion beams as well as the chemical nature of the sample surface during the collision with the primary ion. It is known that using a massive cluster of glycerol [3] or a droplet of aqueous acid [4] enhances the emission of molecule-related ions. And also, it is reported that insulin molecules were ionized without any fragmentation and emitted to vacuum by the impact of neutral SO2 cluster where the average kinetic energy per molecule is about several tens meV [5], which suggested that the chemical property in a large cluster collision play an important role in the ionization of molecules on the surface. Recently, there have been several reports on the effect of the species of gas-cluster projectiles on the secondary ion mass spectrometry, for example, CH4 [6] and H2O [7] gas-cluster projectiles vary the yield of intact ions on the secondary ion mass spectrometry (SIMS).
In this study, we have investigated the secondary ion emission from aspartic acid film using gas cluster ion projectiles generated by argon (Ar), krypton (Kr), water (H2O), methanol (CH3OH), and methane (CH4) gas sources. For the molecular cluster (H2O, CH3OH and CH4) projectiles, intensity of intact ion component enhanced compared with that for the noble gas cluster projectiles. The ratio of the [M+H]+ to the [M+Na]+ intact ion peaks suggested that the molecular clusters, which include protons, assisted the proton attachment to the intact molecule. And also, for the H2O and CH3OH cluster, intact ion was attached with several H2O or CH3OH molecules. In this presentation, effect of the gas cluster species to the secondary ion yields will be discussed. 2. Experimental
Details of the size-selected GCIB ToF-SIMS apparatus are given elsewhere [8]. Large cluster ion beams of krypton (Kr), water (H2O), methanol (CH3OH), methane (CH4), as well as argon (Ar) were produced and used as the projectiles for SIMS. Neutral gas clusters were generated by adiabatic expansion from a nozzle with a 0.1-mm diameter aperture and a 60-mm expansion and cooling zone. For the methane cluster, the methane gas was seeded in the Ar (90% concentration) for cooling. For the H2O and CH3OH clusters are generated from water (99. 9 %, Wako, Osaka) or methanol (99.8 % Wako, Osaka) liquid by bubbling the Ar gas through the liquid at room temperature.
The elemental component in the cluster ion beams was assumed from the change in the component of the background gas in the sample chamber when the beam was on and off, which was measured by the quadrupole mass spectrometer (QMS) equipped with a sample chamber. When the molecular GCIB produced from the target gas mixed with Ar gas enters the sample chamber, the increase of Ar+ is less than several % of that of Ar GCIB, indicating that the main component in the cluster was the target molecular gas.
The samples were formed as thin films on a silicon substrate and no matrix agent was used. An aqueous solution of aspartic acid (1 mg/ml) was dropped onto a silicon substrate and freeze-dried in vacuum. The cluster ion fluence while measuring a SIMS spectrum was below 2.5×1012 ions/cm2. The secondary ion intensities were normalized by the primary ion current.
10
3. Results and discussion Figures 1 show the typical SIMS spectra of aspartic acid bombarded with Ar, CH4, CH3OH,
H2O cluster ion beams. The counts of secondary ions were normalized at the same primary ion current to the peak height of the aspartic acid intact ion [M+H]+ for the Ar cluster bombarding. Mainly two kinds of intact ion [M+H]+ and [M+Na]+ were detected in the spectra. For the molecular cluster bombardment, [M+H]+ component increased. Besides, for the CH3OH and the H2O cluster projectiles, the intact ion attached with several methanol and water molecules become progression respectively. This behavior is similar to the neutral SO2 cluster case where it is claimed that the cluster plays a role of the transient solvent. We also measured the cluster size dependence of the [M+H]+/[M+Na]+ ratio, which indicated that the lower energy per molecule is favorable to the proton attachment.
Figures 1. Typical SIMS spectra under the bombardment of Aspartic acid by the Ar1500+ (a), (CH4)1500+
(b), (H2O)1500+ (c), and (CH3OH)1500+ (d) GCIB at an acceleration voltage of 5 kV. 4. Conclusions
The CH4, CH3OH and H2O cluster ion beams were generated by the adiabatic expansion of the target gas with Ar carrier gas. These beams were used as the projectiles of SIMS. The ratio of the of the [M+H]+ to the [M+Na]+ intact ion peaks of aspartic acid suggested that the molecular clusters, which include protons, assisted in attaching protons to the intact molecule. The lower energy per molecule is favorable to the proton attachment.
References
[1] S. Ninomiya, Y. Nakata, Y. Honda, K. Ichiki, T. Seki, T. Aoki, J. Matsuo, Appl. Surf. Sci. 2008; 55, 1588. [2] K. Mochiji, M. Hahinokuchi, K. Moritani, N. Toyoda, Rapid Commun. Mass Spectrom. 2009; 23,
648. [3] J. F. Mahoney, J. Perel, S. A. Ruatta, P.A. Martino, S. Husain, K. Cook, T. D. Lee, Rapid
Commun. Mass Spectrom., 1991; 5, 441 [4] D. Asakawa, S. Fujimaki, Y. Hashimoto, K. Mori, K. Hiraoka, Rapid Commun. Mass Spectrom.
2007; 21: 1579. [5] C. R. Gebhardt, A. Tomsic, H. Schröder, M. Dürr, K. L. Kompa, Angew. Chem. Int. Ed. 2009; 48,
4162. [6] K. Moritani, M. Kanai, K. Goto, I. Ihara, N. Inui, K. Mochiji, Nucl. Instr. Meth. Phys. Res. B, B,
2013; 315, 300. [7] S. Rabbani, A. Barber, J. S. Fletcher, N. P. Lockyer, J. C. Vickerman, Anal. Chem., 2013; 85,
5654. [8] K. Moritani, M. Hashinokuchi, G. Mukai, K. Mochiji, Electrical Engineering in Japan, 2011; 176,
52.
(c) (d)
(a) (b)
11
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Towards New Applications with CAMECA SIMS Instruments
P. Peres, F. Desse, S.-Y. Choi, A. Merkulov, F. Hillion, F Horreard, M. Schuhmacher*
a Cameca, 29 Quai des Grésillons, 92622 Gennevilliers Cedex, France Email: [email protected]
The NanoSIMS 50L is an original SIMS (Secondary Ion Mass Spectrometry) ion microprobe, optimizing both the primary beam focusing and the secondary ion collection efficiency in order to combine high lateral resolution and high mass resolution capabilities.
In terms of lateral resolution, the surface thermal ionization cesium ion source permits to record ion mapping with a 50nm Cs+ beam carrying 0.5pA. For the analysis of electropositive ions the NanoSIMS design imposes the use of negative primary ions (O- or O2-) with a resolution of 300-400nm, due to the lower brightness of the duoplasmatron primary ion source.
CAMECA already implemented a O2+ RF-plasma ion source from Oregon Physics on its IMS Wf/ SC Ultra SIMS. The high britghness of this source type gives access to Extreme Low Impact Energy (100-150eV) to achieve SIMS depth profiling at depth resolution of 0.7nm/decade with useable sputter rate for routine analysis.
A new RF-plasma ion source optimized for negative oxygen primary ions has been introduced by Oregon Physics and is now available on the CAMECA NanoSIMS 50L as a replacement for the former duoplasmatron ion source option. With this new source the analytical performance in terms of primary ion beam (current density and spot size) is now at the level of the Cs+ beam, thus opening new application fields for the analysis of electropositive elements.
Extreme Low Impact Energy has been demonstrated to be key sputtering conditions for ultra
shallow depth profiling. It is extensively applied for shallow implant characterization, but opens new application fields for thin film analysis. Characterization of graphene structures requires measurements based on various microscopic and spectroscopic techniques. Some of these characterizations aim at determining the number of layers and the purity of sample in terms of absence or presence of defects or doping species.
The information on the defectness of the graphene layer or presence of dopant species can be provided by surface sensitive techniques such as XPS and SIMS. The extreme sensitivity of SIMS to any doping constituents in the surficial layer combined to Extremely Low Impact Energy protocole could provide important information, difficult to obtain by other techniques.
SIMS technique is mature enough to be used as a high volume analysis metrology tool
provided that the instrumentation offers a high level of automation. The CAMECA IMS 7f-Auto combines the field proven instrumental advantages of the former CAMECA SIMS tool generation (unparalleled depth profiling capabilities, extreme sensitivity and high mass resolution for best detection limits,…) with additional developments towards improved automation and operation efficiency.
The IMS 7f-auto offers a redesigned, in-line primary column specifically developed in order to optimize the ease of use, and to enhance the reproducibility of the instrument by minimizing operator-related biases. Another new feature is a motorized storage chamber that keeps under vacuum up to six multi-windows sample holders. The full automation of sample holder transfer allows unattended or remote mode analyses, thus significantly improving the analysis throughput of the tool.
14
Twenty-Five Years of Advances in
TOF-SIMS Instrumentation and its Application
Markus Terhorst and Derk Rading
ION-TOF GmbH, Heisenbergstr. 15, 48149 Münster, Germany
ION-TOF has just celebrated its 25th anniversary after being founded as a University spin-off
from Prof Benninghoven's research group back in 1989. Since then, a tremendous instrumentation
development has been driven by ION-TOF. Major achievements include the transition from pure
surface analysis to state-of-the-art depth profiling and 3D analysis by the introduction of the dual-
beam technique as well as the continuous development of advanced cluster ion sources utilizing firstly
SF5, later Aun and C60, and finally Bin and large Ar clusters.
More recently, the time-of-flight analyzer could be improved in such a way that TOF-SIMS is
more and more replacing classical dynamic SIMS instruments for the depth profiling of inorganic
materials by using the so-called EDR technology. Also, a TOF-SIMS / AFM combination instrument
has been developed for the in-situ characterization of chemical composition and surface topology,
respectively. The dedicated and uncompromised integration of a FIB source serving for in-situ sample
preparation and tomography will be described in more detail in another presentation at this meeting.
The commercial success � especially over the last 15 years � has been a logical consequence
of our product development history described above: ION-TOF has now more than 260 TOF-SIMS
instruments installed word-wide.
In this presentation, the latest developments will be summarized and typified by selected
examples from various applications fields.
15
TOF-SIMS apparatus having function of Laser-SNMS
for nano-scale mass imaging
T. Kashiwagi
Toyama Co., Ltd, 4-13-16 Hibarigaoka, Zama, Kanagawa 252-0003, Japan
� Secondary Ion Mass Spectrometry (SIMS) is mass spectrometry to detect secondary ions generated
from solid surface with irradiation of ion beam, and combines high sensitivity and high spatial
resolution. Therefore, SIMS is widely used to analyze depth profile of semiconductor dopant element,
component of contamination, and composition of functional particulate included organic compounds,
etc. However, since subject of analysis becomes smaller and smaller by year, analysis is becoming
difficult. It's because SIMS method is a destructive analysis, amounts of usable atoms and molecules
is limited in small filed of view, and nominal upper yield of secondary ion is less than 1/1000 of all
the atoms and molecules sputtered by the ion beam.
� Then, We have developed TOF-SIMS apparatus "FILMER (Focused-Ion-Beam Laser nano Mass
Imager)" having function of Sputtered Neutral Mass Spectrometry by Laser-Post Ionization (Laser-
SNMS) for nano-scale mass imaging under the grant aid of Japanese Science and Technology Agency
(JST).[1] Laser-SNMS is a method that neutral atoms and molecules sputtered by FIB are photo-
ionized with high efficiency under high intensity pulse laser irradiation, and can detect a small quantity
of inorganic elements and organic compounds with high sensitivity in principle.
� � In this talk, we will introduce a few examples of mass images of a small quantity of elements,
and organic compounds in micro-meter region by Laser-SNMS. Also, mass spectrum of SIMS are
given using our apparatus with improved mass resolution.
� � � � � � Fig.1 Laser-SNMS apparatus "FILMER"� � � � � Fig.2 Laser-SNMS Image of Blend Polymer(PS/PHS)
[1] M. Fuji, T. Sakamoto, Chemistry &Chemical Industry, 2010, 802
4 µm�
n
n
OH
m/z = 104�
m/z = 120�
16
Recent progress o
T. Miyayam1 ULVAC-PHI, Inc.,
2Physical Electronics,
Molecular imaging capabili
spectrometry. Time-of-flight second
for the molecular imaging such as h
However, the conventional
to achieve high spatial resolution an
acquire a high quality mass image a
PHI TRIFT V nanoTOF
cluster liquid metal ion gun (LMI
density primary cluster ion beam p
(>10,000 m/ m at 28
Si or 28
SiH) at
collect most secondary ions genera
wide angular acceptance, so that m
effect.
In this presentation, we wi
ULVAC-PHI, including a new LM
ion gun for ultra-shallow depth prof
Figure 1
t progress of ion beam technologies in ULVAC
Miyayama1, S. Iida
1, N. Sanada
1 and G. L. Fisher
2
HI, Inc., 370 Enzo, Chigasaki, Kanagawa, 253-8522, Jap
ctronics, 18725 Lake Drive East, Channhassen, MN55317
capability is now one of the most important properties
flight secondary ion mass spectrometry (TOF-SIMS) has va
ng such as high spatial resolution, high mass resolution and h
onventional TOF-SIMS instruments have usually two analytic
resolution and high mass resolution respectively. This means
ass image and a high quality mass spectrum separately.
noTOF has improved its molecular imaging capability as
n gun (LMIG). The new design of lens column can provi
ion beam pulse, high lateral resolution (
Comparison of Measurement Repeatability among Beam position alignment, Z-direction motion, and Auto-beam centering using a Cameca
IMS 7f instrument
S. Miwa Cameca bu. Ametek Co. Ltd., Shiba NBF Tower 1-1-30 Shibadaimon Minato-ku, Tokyo 105-0012
Japan; [email protected]
1. Introduction
Measurement repeatability on SIMS is one of important problems. Magnetic sector SIMS instruments like Cameca IMS xF require high voltage at the sample holder. So that collected secondary ions are strongly affected by the variation of the electric field between the sample holder and the extraction lens (immersion lens). The reasons of the variation of electric fields are change of gap between sample and the immersion lens, edge effects of the sample holder or sample windows, tilt of samples, differences of potential inside samples, and so on. In this work the author discusses the influence of height differences using a Z-motion (to change the gap between sample holder and immersion lens). The author also shows the effect by the modification of secondary ion trajectory using deflectors (DT-FA, DT-CA) located in the secondary ion optics. 2. Experimental
All measurements were performed using a Cameca IMS 7F instrument. Highly B doped Si wafer and As implanted Si wafer were prepared and 4 pieces of 8 mm square samples were cut from the wafers. They were mounted on a 4 windows sample holder. 3 different beam centering methods were applied and the repeatability for each method was calculated from 8 measurements (2 for each sample window). First method was used only primary beam centering by adjusting primary beam deflectors, second one was used Z-motion (sample height adjustment) instead of primary beam deflector of X-direction, and third one was beam centering of secondary ions both for imaging plane and cross over. Sample detail and measurement conditions are shown in Table 1. The measurement positions were chosen near the center of the window in order to avoid window edge effect. 3. Results and discussion
Measured As dose and average B concentration are shown in Table 2. RSD (i.e. measurement repeatability) was calculated from these values and they are also shown in Table 2. RSFs used were calculated from each first measurement (window 1 1st). In the case of As dose measurements repeatability is improved by controlling sample height as shown in Table 2. In fact the differences of height in the surface of the sample holder used is more than 50 µm which is confirmed by the variation of primary beam position; [height difference] = [variation of primary beam position] / tanθ (θis incidence angle of primary ions.). However, in the case of B concentration height control is not effective as shown in Table 2. The pass energy of secondary ions used for As detection was narrower than that of B detection and As was detected as cluster ions AsSi- which energy distribution is also narrower than atomic ions (B+). This means that the immersion lens focuses sharper and focusing is more sensitive for the difference of sample height (i.e. focal length). Third method is modification of secondary ion trajectory which is realized by two set of deflectors and give well repeatability as shown in Table 2. One set of deflectors is called DT-FA and can move image plane of secondary optics. This function is identical to movement of primary beam position. Another is called DT-CA and is located in between two transfer lenses. This can change ion trajectory against cross over (contrast aperture position). Optimum values of these deflectors can be automatically decided from intensities of detectors, which is called auto beam-centering. This function plays an important role to obtain stable secondary ions. Moreover it is effective even for the measurements of B, which analytical conditions are wide pass energy and large contrast aperture (wide entrance slit), as shown in Table2.
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4. Conclusion Sample height adjustment can improve the measurement repeatability when the pass energy of
secondary ions is narrow. Beam centering technique of secondary trajectory is effective to improve the measurement repeatability even in the case of wide pass energy of secondary ions. Acknowledgement
The author would thank Dr. Miyazaki of Tohoku univ. for his kind supports. Table 1. Sample detail and Measurement Conditions.
Sample detail Sample detail implanted species 75As+
dopant B
energy 160 keV
resistivity 0.001-5 Ωcm dose 1.15E14 cm-2
concentration 5E19 cm-3
Measurement conditions Measurement conditions Primary ions Cs+
Primary ions O2+
Primary acceleration Voltage 10 kV
Primary acceleration Voltage 15 kV Primary beam current 100 nA
Primary beam current 500 nA
Raster size 150 µm Raster size 200 µm
Analysed area size 33 µm Analysed area size 65 µm
Sample voltage -5 kV
Sample voltage +5 kV Mass resolution 4000 (50%)
Mass resolution 400 (50%)
Energy window 30 eV
Energy window 150 eV Detected ions 103SiAs-, 86Si3-
Detected ions 11B+, 28Si+
Table 2. Results of measurement repeatability.
As dose (cm-2)
B concentration (cm-3)
position
meathod 1 meathod 2 meathod 3
meathod 1 meathod 2 meathod 3
Window 1 1st
1.15E+14 1.15E+14 1.15E+14
5.00E+19 5.00E+19 5.00E+19 Window 1 2nd
1.15E+14 1.16E+14 1.15E+14
5.02E+19 4.98E+19 5.00E+19
Window 2 1st
1.13E+14 1.14E+14 1.14E+14
4.95E+19 4.88E+19 4.94E+19 Window 2 2nd
1.12E+14 1.14E+14 1.14E+14
4.99E+19 4.89E+19 4.94E+19
Window 3 1st
1.15E+14 1.16E+14 1.16E+14
4.97E+19 4.91E+19 4.98E+19 Window 3 2nd
1.15E+14 1.16E+14 1.16E+14
4.98E+19 4.94E+19 4.99E+19
Window 4 1st
1.14E+14 1.15E+14 1.14E+14
4.89E+19 4.86E+19 4.90E+19 Window 4 2nd
1.13E+14 1.15E+14 1.14E+14
4.90E+19 4.90E+19 4.92E+19
RSD (%)
0.99% 0.83% 0.55%
0.91% 1.00% 0.80% method 1 : primary beam centering by adjusting primary beam deflectors method 2 : Z-motion (height adjustment) instead of primary beam deflector of X-direction method 3 : beam centering of secondary ions both for imaging plane and cross over
19
Reduction of phosphorus ion yield by electron beam irradiation under O2 primary ion bombardment
Y. Hori *(1), M.Saruwatari (1) and M.Tomita (2)
1 Physical Analysis Technology Center, Toshiba Nanoanalysis Corporation, 1, Komukai-Tohiba-Cho,Saiwai-ku,Kawasaki 212-8583 Japan;
2 Corporate Research & Development Center, Toshiba Corporation, 1, Komukai-Tohiba-Cho,Saiwai-ku,Kawasaki 212-8582 Japan;
*[email protected] 1. Layout and file settings
It is general for phosphorus depth profiling in silicon with SIMS to use Cs+ primary ion because it provides high secondary ion yield. But when low primary ion energy is used in order to improve depth resolution, Cs+ primary ion has some problems to evaluate phosphorus with accuracy.
The measurement with O2 primary ion makes it possible to improve secondary ion yield with full
oxidized condition of the sputtered surface for phosphorus depth profiling in silicon. This analytical method can get better detection limit than that of Cs+ primary ion because secondary ion yield of 30Si+H relatively become lower than that of phosphorus. Furthermore, transient region and depth resolution with O2 primary ion is better than those with Cs+ primary ion at the same primary ion energy[1]. Therefore, the measurement with O2 primary ion becomes a candidate for solution of the problems.
In the measurement for phosphorus in silicon, it turns out that a reduction of phosphorus ion yield occurs under O2 primary ion bombardment with an electron beam irradiation, which is used for multiple layer samples with silicon and insulator films (Fig. 1). The significant reduction of phosphorus ion yield was observed only under fully oxidized condition of the sputtered surface, but it was not caused by the Gibbsian segregation effect. We speculate that the cause of the reduction is vaporization of POx from the sputtered surface and we investigated the correct evaluation method for phosphorus depth profiling in silicon layer with high depth resolution.
[1] M.TOMITA, Y. KAWAMURA, Y. SHIMIZU, M. UEMATSU AND K.M. ITOH, ABSTRACT OF SIMS XVII, P332 (2009).
102
103
104
105
106
0 50 100 150 200
Sec
on
dar
y io
n in
ten
sity
(co
un
ts/s
)
Depth (nm)
P-doped poly-Si SiO2
Si-sub.
P- without E-gun
P- with E-gun
Si-
Fig. 1 Depth profiles of phosphorus doped silicon sample under O2 primary ion bombardment with and without electron beam
20
Deconvolution of Depth Profiles of GaN-Based Light Emitting Diodes with Tunnel Junctions
Y. Nakata1, N. Morita1, J. Sameshima1, M. Yoshikawa1 and T. Takeuchi2
1Toray Research Center Inc., 3-7, Sonoyama 3-chome, Otsu, Shiga 520-8567, Japan 2Fac. Sci. & Eng., Meijo University, 1-501, Shiokamaguchi, Tenpaku-ku, Nagoya, Aichi, 468-8502,
Japan [email protected]
1. Introduction
GaN-based semiconductors have been developed in optoelectronic and high-power electronic devices in the past decades because of their wide direct bandgap. However, their full potential is limited by low hole concentration and high resistivity of p-type layers. One of the solutions to these issues is hole injections through GaN-based tunnel junctions [1,2]. Typically, the tunnel junctions require extremely high-impurity concentrations in very thin p-n junctions. Dynamic SIMS (D-SIMS) is a powerful technique for quantification of matrix and impurity concentrations in such thin layers because of its high sensitivity. However, one of the problems in D-SIMS analysis is the artificial broadening of profiles caused by atomic mixing and ununiform surface morphology. An alternative approach is deconvolution of the profiles using the depth resolution function, which is often experimentally determined by measuring delta doped layers. In this work, we measured Mg and Si depth profiles in the aforementioned GaN-based LED using Cs+ primary beam. For better understanding of the profiles, the deconvolution technique was carried out using the mixing-roughness-information depth model, or MRI model proposed by S. Hofmann [3,4]. 2. Experimental
Figure 1 shows an example of LED structures with tunnel junction supplied by Meijo University [5]. The tunnel junction consists of Si-doped n++ and Mg-doped p++ GaN layers, which enable the hole injection through a reverse bias voltage. The tunnel junction needs very high doping concent-rations (> ~1020 atoms/cm3) in very thin layers [2]. This type of LED can minimize thickness of p-type layers and facilitate current spreading at the surface layer.
D-SIMS was carried out using a CAMECA IMS-6f ion microscope. The Cs ion source was operated at + 10 kV and the sample was biased at + 4.5 kV, resulting in an impact energy of 5.5 keV. The angle of incidence was 42º with respect to the surface normal. The analysis was performed with a primary ion current of 15 nA and scanning area about 150 µm × 150 µm, the field aperture 60 µmΦ. The base pressure of the analytical chamber was typically 1 × 10–7 Pa.
In general, the depth profiling of Mg and Si in compound semiconductors is separately taken by detecting CsMg+ and Si-, respectively. However, in order to evaluate the performance of the tunnel junction, it requires information about overlapping region of p-type (Mg) and n-type (Si) profiles. In this work, we simultaneously took both Mg and Si profiles in the tunnel junctions with a use of Cs+ primary beam by detecting CsMg+ and Si+. 3. Deconvolution of depth profiles
Depth profiling can be described by the convolution of the true dopant distribution X(z’), with the depth resolution function g(z-z’), thus the normalized intensity I/I0 is given by:
n++ GaN:Si (30 nm)
p++ GaN:Mg (7.5 nm)
GaN:Mg (50 nm)
AlGaN:Mg (20 nm)
GaInN/GaN 5QWs (2.5/15nm)
LT-GaN
C-plane Sapphire
n-GaN:Si (540 nm)tunnel junction
active layer
n-GaN:Si (3000 nm)
GaN (3000 nm)
Fig. 1 Schematic diagram of LED structure with GaN-based tunnel junction.
21
The MRI method is capable of giving a mathematical description of the depth resolution function based on the three contributions of atomic mixing (w), surface roughness (σ) and information depth (λ) as follows: The MRI parameters can be predicted theoretically and/or measured experimentally because each parameter has a well-defined physical meaning. In this work, the surface roughness was assumed to be 2 nm, and the atomic mixing parameter was derived from the empirical approximation for Cs+ ions: gw = 1.838E0.68 cosθ [6]. The information depth in SIMS can often be neglected as demonstrated in successful applications of the MRI model to SIMS profiles [7], therefore the parameter λ was assumed to be zero. 4. Results and discussion
Figure 2 shows the result of SIMS depth profiling of the GaN-based LED with tunnel junction. Both the Si and Mg are highly doped at more than 1e20 atoms/cm3 in the range of 380-420 nm in depth and therefore the tunnel junction is considered to be formed at the interface of the Si doped (n++) and Mg doped (p++) layers. It is noted that the n++ layer still contains p-type dopant (Mg) at relatively high concentration, which might influence the tunnel current and deteriorate the LED efficiency. To evaluate the tunnel junction in more detail, the deconvolution procedure was carried out in Fig. 3. The reconstructed Mg profile exhibits a relatively sharp distribution, reaching the maximum concentration more than 3.5e20 atoms/cm3. However, it shows that the Mg and Si profiles are overlapping at their interface ranging from 405 to 410 nm in depth, which could be an obstacle to achieving a lower resistivity of the tunnel junction. It indicates that the device efficiency could be improved by precisely controlling the dopant profiles and obtaining a thinner tunnel junction. In the future, we will examine the model employed here and investigate the depth resolution function by measuring the delta doped layer in the GaN-based system. References [1] S.-R. Jeon, Y.-H. Song, H.-J. Jang, G. M. Yang, S. W. Hwang, and S. J. Son, Appl. Phys. Lett. 78 (2001) 3265. [2] T.Takeuchi, G. Hasnain, S. Corzine, M. Hueschen, R. P. Schneider, Jr., C. Kocot, M. Blomqvist, Y.-L. Chang, D. Lefforge, M. R. Krames, L. W. Cook and S. A. Stockman, Jpn. J. Appl. Phys. 40 (2001) L861. [3] S. Hofmann, Surf. Interface Anal., 21 (1994) 673. [4] S. Hofmann, Surf. Interface Anal., 30 (2000) 228. [5] M. Kaga, T. Morita, Y. Kuwano, K. Yamashita, K. Yagi, M. Iwaya, T. Takeuchi, S. Kamiyama, and I. Akasaki, Jpn. J. Appl. Phys., 52 (2013) 08JH06. [6] Y.N. Drozdov, M.N. Drozdov, A.V. Novikov, P.A. Yunin, D.V. Yurasov, J. Surf. Invest. 6 (2012) 574. [7] S. Ootomo, H. Maruya, S. Seo, F. Iwase, Appl. Surf. Sci., 252 (2006) 7275.
Fig. 2 SIMS depth profile of the GaN-based LED with tunnel junction.
○ SIMS exp. [Si]× SIMS exp. [Mg]－ MRI fit.
reconstructed depth distribution of Mg
reconstructed depth distribution of Si
Fig. 3 Reconstruction of Mg and Si depth profiles in the GaN-based tunnel junction.
, ,
22
Light element analysis in oxide and nitride materials
M. Hashiguchi1, I. Sakaguchi1, K. Watanabe, N. Saito, T. Suzuki, Y. Adachi1, N. Ohashi1, 2 and S. Hishita1
1 National Institute for Materials Science (NIMS), 1-1 Namiki Tsukuba, 305-0044 Japan 2 Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259
Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan [email protected]
1. Introduction
In semiconductor field, quantitative analysis of concentration of light element, such as hydrogen, carbon, nitrogen, and oxygen, is very important for characterization and evaluation of oxide and nitride materials. Secondary ion mass spectrometry (SIMS) is useful tool for the quantitative analysis of light elements. In such case, the high-quality sample and ion implantation technique are the key technique to achieve the quantitative analysis of SIMS [1]. The high-quality thin films were fabricated by using the pulsed laser deposition (PLD), chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). However, the thin films were usually contained the unintentional impurity such as hydrogen in CVD-diamond [2] and oxygen in ScN deposited by MBE, and the electrical property was influenced by the impurity. In field of electroceramics, the reducing atmosphere was usually used to prevent the oxidation of inner electrode in the BaTiO3 devices. It is an important to reveal hydrogen incorporation reaction into BaTiO3, and the oxygen diffusion paths (oxygen vacancy) reflected the hydrogen incorporation in BaTiO3 [3].
We applied two methods to detect the light elements such as hydrogen and oxygen in materials. One is the raster reduction of primary ion beam and is effective to check the hydrogen and oxygen signals in the bulk [3] and hard thin film [4] samples. However, this method is impossible to apply the thin films. Another method is the use of the broad primary beam and is applied to detect hydrogen in BaTiO3 [3]. Above methods are effective to judge the background and real intensities of hydrogen and oxygen in the current analysis. In this paper, we applied the broad primary beam to check the oxygen impurity in GaN thin film.
2. Experimental Methods
GaN thin films deposited by chemical vapor deposition were purchased from the company. 16O+ ions were implanted into the GaN thin films at room temperature. Implanted dose of 16O+ ions were 4x1016 and 5x1015 ions/cm2 and the accelerated voltage was with 50 or 150 keV, respectively. Before and after the ion implantation, sample surface of the films were observed by Atomic Force Microscope (AFM) to investigate change of surface morphology by the ion implantation.
Depth profiles of oxygen in samples were obtained by SIMS (Cameca ims-4f). The sample surface was homogeneously irradiated on ~ 100 µm by a static Cs+ primary beam. The ion beam currents were changed in the range of 5 - 20 nA. Secondary ions are extracted from the sample surface at 4.5 keV. We obtained both of negative and positive secondary ions from the samples. Contrast aperture of 150 or 50 µm were used to define the measurement area. Concentration of 16O- ions in the GaN films was evaluated using relative sensitivity factors (RSFs). 3. Results and Discussion
AFM observations of the O-implanted GaN thin films were revealed that the surface morphology was changed after O ion implantation (Figure 1). Roughness of the sample surface decreased after the ion implantation. The roughness were ~15 nm before ion implantation and ~13 nm and ~7 nm after the implantation of 5x1015 and 4x1016 ions/cm2 of O ions, respectively.
Figure 2 shows the depth profiles of a GaN implanted with 5x1015 ions/cm2 of 16O+ ions. The analysis was carried out the normal atmospheric condition in the chamber. The O concentrations of the sample were measured by the profiles as ~3x1020 ions/cm3 at the depth of ~200 nm. It is found that the oxygen concentration near the surface is significant high sue to the stop process in the fabrication and the oxidation in the air atmosphere. The tailing regions of these profiles are the oxygen background intensities, because we evaluated the oxygen concentration of about 5x1016 ions/cm3 by the raster reduction method. In Figure 2, the background of these depth profiles decreased with increase of
23
primary ion intensity, by a factor of about two. We would like to discuss the oxygen background in GaN thin film as a function of primary beam intensity, irradiation area, the atmospheric condition in the chamber.
Figure 2. Depth profiles of a GaN implanted with 5x1015 ions/cm2 of 16O+ ions obtained by Cs+ primary ion of ~ 100 µm diameter with 5 nA and 20 nA. Profiles of O concentration evaluated using RSF.
Acknowledgement
Part of This study was performed for the Elemental Strategy Initiative conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. References [1] Y. Homma et al., J. Appl. Phys., 57, 2931, (1985). [2] I. Sakaguchi et al., J. Appl. Phys. Lett., 71, 629, (1997). [3] I. Sakaguchi et al., Jpn. J. Appl. Phys., 51, 101801, (2012). [4] T. Nakagawa et al., Jpn. J. Appl. Phys., 46, 3391, (2007).
Figure 1. AFM images of surface of GaN thin films (a) before ion implantation. and (b) after implanted with 5x1015 ions/cm2 of 16O+ ions.
24
Q-SIMS analysis of impurities in SnO2 layer on glass substrate
T. Abe Sekine, T. Suzuki
Reserch Center, ASAHI GLASS CO., LTD., 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa
221-8755 Japan;
1. Introduction
Transparent conductive layer (TCO) is widely used in industry for photovoltaic, low emissivity glass
and so on. Impurities in TCO have a strong relationship with the electronic and optical properties.
Especially, the contaminations of H, Cl and F in SnO2 film are known to affect the crystalline and
electronic properties [1]. Therefore, it is important to understand the impurity concentration in TCO
layers.
Quadrupole Secondary Ion Mass Spectrometer (Q-SIMS) is powerful to investigate trace impurities
in inorganic materials, however, it is known that surface charge causes a large statical error for the
quantitative evaluation with the SIMS depth profile [2]. In order to obtain the accurate SIMS depth profile
for nonconductive or semi-conductive materials, it is necessary to optimize a variety of measuring
conditions, such as neutralization of surface with electron beam, conductive layers, and so on [3].
In this study, we have investigated that the SIMS depth profiling condition of H, Cl and F in SnO2
layer on glass, especially to optimize the filtering voltage of secondary ion energy, which is effective to
calibrate the inducing energy of the secondary ion varied by the surface charge.
2. Experimental
F doped SnO2 layer (thickness: about 700 nm) on glass substrate was manufactured by chemical vapor
deposition (CVD) process. SIMS measurements were carried out using Q-SIMS (QHI ADEPT1010).
The samples were settled with the cover of metal mask on the holder of zero potential, while the
neutralization of the surface charge was not performed with the electron beam. The Cs+ primary beam
impact energy was chosen to be 3 keV and the beam current to be 150 nA. Negative secondary ions
were detected with an incidence angle of 60° to the sample surface. The secondary ions, 1H-, 19F-, 35Cl-
as trace impurities and (120Sn+16O)- as a matrix were monitored during depth profiling. Quadruple lens
conditions were aligned to obtain maximum intensity of 120Sn+16O- when energy filter voltage was 180
eV. The operation condition of energy filter voltage (165-180 eV) was changed for the trace impurities
(H, F, Cl). Standard errors were evaluated among 10 times interval measurements for each condition.
25
3. Results and discussion
Figure 1 shows the correlation of energy filter
voltage vs. Cl intensity and error of 10 times
measurements. This result suggests that the maximum
intensity and the minimum standard error are obtained
with the optimization of energy filter voltage with
172-174 eV. For the precise estimation of impurity
concentration in TCO film, it is necessary to obtain the
maximum intensity of secondary ions.
Figure 2 shows the correlation of energy filter
voltage vs. error for the intensity of H, Cl and F. There
is no difference in the error for the intensity of H with
the energy filter voltage (170-180 eV). On the other
hand, it is confirmed that minimum error for the
intensity of Cl is achieved at 172 eV, and that of F is
achieved under 168 eV while the other parameter is
almost fixed. These results suggest that the
optimization of energy filter voltage is effective to
obtain the reliable data of Cl, F concentration, which
implies that the calibration for the inducing energy of
the secondary ion is important to obtain the accurate
SIMS depth profile for the impurities in TCO. Optimal
energy fi
