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Comparing XRD data for 225C and 300C growth of Si-Heusler.
Some composition assumption for sample grown at 225C.
S230 grown at 300CSi Comp = 22.9 at.%
S239 grown at 225CSi Comp = 27.8 at.%
1009080706050Co Percent Metal
1.0
0.8
0.6
0.4
0.2
0.0
x10
-2
4.10
4.05
4.00
3.95
3.90
0.12
0.10
0.08
0.06
0.04
0.02
0.00
1.003
1.002
1.001
1.000
0.999
0.998
0.997
In-P
lan
e P
ositio
n
4.0
3.5
3.0
2.5
2.0
1.5
1.0
In-P
lan
e F
WH
M 1
0-2
1.0
0.8
0.6
0.4
0.2
x10
-3
2.06
2.04
2.02
2.00
1.98
1.96
1.94
5
4
3
2
1
0
x10
-4
1.03
1.02
1.01
1.00
0.99
0.98
0.97
Integrated Intensity
Peak Position [rlu]
Peak FWHM [rlu]
L(014)h=(022)c K(014)h=(022)c L(102)h=(002)c L(011)h=(111)c
Int=0.0069
1009080706050Co Percent Metal
2.5
2.0
1.5
1.0
0.5
0.0
x10
-2
4.10
4.05
4.00
3.95
3.90
0.12
0.10
0.08
0.06
0.04
0.02
0.00
1.003
1.002
1.001
1.000
0.999
0.998
0.997
In-P
lan
e P
ositio
n
4.0
3.5
3.0
2.5
2.0
1.5
1.0
In-P
lan
e F
WH
M 1
0-2
3.0
2.5
2.0
1.5
1.0
0.5
0.0
x10
-3
2.06
2.04
2.02
2.00
1.98
1.96
1.94
1.5
1.0
0.5
0.0
x10
-4
1.03
1.02
1.01
1.00
0.99
0.98
0.97
Integrated Intensity
Peak Position [rlu]
Peak FWHM [rlu]
L(014)h=(022)c K(014)h=(022)c L(102)h=(002)c L(011)h=(111)c
Things I noticed:• (022) intensity higher for 225C growth at Heusler Comp• Large area of higher intensity and in-plane lattice matching (65-
90)%Co– FWHM shows similar trend
• No Significant difference in in-plane peak width for the two growth temperatures
• (111) very wide at 225C growth• On the 300C sample, the strain is different for each reflection (the
position traces do not collapse on top of each other) wereas they agree in the 225C sample
• Comparing Zero Strain w/Si concentration suggests zero strain if Si was 25at%
• Zero Strain doesn’t necessarily correspond with highest intensity of narrowest peak
Comparing Chemical Order
3
4
5
67
0.01
2
3
4
5
67
0.1
2
3
4
Inte
nsi
ty R
atio
1009080706050Co Percent Metal
S1/F (300C) S2/F S1/F (225C) S2/F
The idea here is to measure the chemical ordering qualitatively. I’ve divided the integrated intensity of each superlattice peak by the fundamental to remove variations in structural disorder.
F=(022)c=(014)hS1=(002)c=(102)hS2=(111)c=(011)h
•No significant changes in intensity within the “good” region (65-85)% Co•No difference in S1/F for the two temperatures•Significant difference in intensities for S2/F: the (111) peak is MUCH stronger relative to the fundamental peak for 300C growth
Comparing phi-scan FWHM• Voigt could not fit well, so I found
FWHM via max value and located max/2 in the data after background subraction
• S239 had 2 components probably due to 2 distinct populations of grain sizes. I fit the wider as a polynomial background
• Clearly, the sample grown at 225C has a narrower width at the Heusler composition
FWHM vs Comp at Two Growth Temps
Example of two components in s239 Heusler Stoichiometry Data Compare
2
3
4
567
1
2
3
4
Ph
i-Sca
n F
WH
M [D
eg
]
1009080706050Co Percent Metal
s239 (225C) s230 (300C)
8
6
4
2
No
rmed
In
ten
sity
x 1
0-3
26.025.024.023.022.021.0Phi [Deg]
Data Fit Bkg
Voigt Fit: |X|² = 2.8973Intensity: 0.001946 ± 3.8349e-05Amplitude: 0.0059389 ± 6.5139e-05Position: 23.803 ± 0.00096075FWHM: 0.2086 ± 0.0034152Shape: 10000 ± 0
0.3
0.2
0.1
0.0
No
rmed
In
ten
sity
26.025.024.023.022.021.0Phi [Deg]
s239 (225C) s230 (300C)
L-scans of (014) on s231 (Si~19at%)Grown at 150C and 1/3 as Thick as Others
• A couple bad spots at ~90% Co• Zero strain @ ~84% Co• Position/Strain changes monotonically/linearly• Width strange
4.08
4.06
4.04
4.02
4.00
3.98
3.96
3.94
Pos
ition
[rlu
]
1009080706050Co Percent Metal
60
55
50
45
40
35
FW
HM
[rlu 10-3]
6810
-4
2
4
6810
-3
2
4
68
Integrated Intensity
Some General Conclusions• Si-concentration is a bigger factor to determine strain than Co/Mn
ratio• Higher Co concentration is better ordered than Heusler
stoichiometry regardless of growth temp according to intensities• Large region of composition gives good ordering according to peak
widths• These samples are still too different to make a definitive statement
on growth temperature– Different Si concentrations– Different layer ordering when grown– Different thicknesses (at least the 150C sample)
• Improving the study:– Study Si-dependant samples– Grow all three samples in a immediately after each other rather than
venting or composition recalibration to ensure const Si btwn samples
S241: Ternary Sample Grown at 225C
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
20
15
10
5
0
L In
ten
sity 10
-3
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
10
8
6
4
2
0
K Inte
nsity 1
0-3
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
4
4
3.97 3.96
4.02
4.00
3.98
3.96
3.94
L P
osition
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
1.000
0.998
0.996
K P
ositio
n
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
807060504030
L F
WH
M 10
-3
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
35
30
25
20
15
K F
WH
M 10
-3
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
0.5
0.4
0.3
0.2
0.1
0.0
L S
hap
e
43
21
0X
Po
s [m
m]
6420 Y Pos [mm]
0.5
0.4
0.3
0.2
0.1
0.0
K S
ha
pe
• L and K scans of the (014) reflection
• Phi scans are difficult to fit – just calc FWHM from data
• Data taken at corner of ternary sample nearest Co Apex
• Along Diagonal boundary, Co~80% of metal concentration
• Along base, Si~10%
In-Plane Out-of-Plane4
32
10
X P
os
[mm
]
6420 Y Pos [mm]
1.0
0.8
0.6
0.4
0.2F
WH
M [D
eg
]
Phi-scan FWHM
Ternary General Conclusions
• Brightest peaks correspond with narrowest width which occurs at the edge of the region corresponding to Co 80% (out of metal concentration). This is the spot of best crystal structure
• Best crystal structure DOES NOT correspond to zero strain, OR Heusler Stoichiometry
• Don’t know Si concentration yet
XRF Analysis of s238,39,41
Used to tweak first slide’s results and to correlate structural data
XRF analysis on binary samples: s238(150C), s239(225C)
• Compared XRF thicknesses w/ AA monitor – Quartz crystal expected thickness during growth– Both samples came to significantly
lower thicknesses– Since reduction ~ same for each
element, composition was not effected significantly
– This is NOT effected by Duke profilometer readings, since both are calibrated to the same calibration sample and same measured sample thickness
• Fluctuation seems fairly large for Si and Co between the two samples. Mn held steady.
900
800
700
600
500
400
300
200
Thi
ckn
ess
[Å]
-6 -4 -2 0 2 4 6Sample Position [mm]
Film ThicknessSi-Heusler Number Density
s239 s238Expected: 700Å, 687Å
800
600
400
200
0
Thi
ckn
ess
[Å
]
-6 -4 -2 0 2 4 6Sample Position [mm]
s239 Component ThicknessesAssuming Si-Heusler Number Density
Co Mn Si TotalCmpr to Calc: (81%, 88%, 85%, 84%)
800
600
400
200
0
Thi
ckn
ess
[Å
]
-6 -4 -2 0 2 4 6Sample Position [mm]
s238 Component ThicknessesAssuming Si-Heusler Number Density
Co Mn Si TotalCmpr to Calc: (85%, 88%, 81%, 79%)
Mn pos way off again!
Binary Compositions
• Despite fluctuations, the offset of the Mn in s238 seems to have compensated and produced similar Si-concentrations
• Although Si is higher as expected, Co/Mn=2 pos changed and gives near zero strain (see slide 1)
• NOTE: we have no structural data (RHEED or XRD) on s238.
100
80
60
40
20
0
Com
po
sitio
n [a
t.%
]
-6 -4 -2 0 2 4Sample Position [mm]
0.1
2
4
6
81
2
4
6
810
Meta
l Ra
tio
s239 Si Heusler CoPercent MnPercent SiPercent MetalRatio
Co/Mn=2@ x=-0.4
Si=27.8 at.%
100
80
60
40
20
0
Com
po
sitio
n [a
t.%
]
-6 -4 -2 0 2 4 6Sample Position [mm]
0.1
2
4
681
2
4
6810
Meta
l Ra
tio
s238 Si Heusler CoPercent MnPercent SiPercent MetalRatio
Co/Mn=2@ x=0.1
Si=27.9 at.%
XRF analysis on Ternary• Composition values obtained and
used to correlate structural results between samples.
• Quantitative thickness comparisons detailed in table at bottom right.
• Total thickness comparison for s241 is better, giving 95% the expected value.
• Co is nominally the same low value seen in other samples
• Mn thickness matches expected here, giving large fluctuation from binary samples
• Si thickness measurement was very low even though Liang had tried to increase the Si amount
64
20
-2-4
Y P
os [m
m]
-6 -4 -2 0 2 4 6X Pos [mm]
Si
Mn
Co
15
20
25
30
35
40
45
50
3035
40
45
50
55
6065
70
15
20
25
30
35
40
45
50
55
Film CompositionAtomic Percent
64
20
-2-4
Y P
os [m
m]
6420-2-4-6X Pos [mm]
400 390
380
380
370 370
370
360
360
360 350
350
350
370
360
350
390
380
370
360
350
To
tal T
hickness [Å
]
Total Thick Calc: 390Å; (95%)Co Max: 262Å; Calc: 307Å (85%)
Min: 100Å; Calc: 115Å (87%)MnMax: 223Å; Calc: 225Å (97%)
Min: 39Å; Calc: 39Å (100%)Si Max: 206Å; Calc: 261Å (79%)
Min: 40Å; Calc: 44Å (91%)
Curiosity: Co Zero Line Misalignment
• Co Zero line seen here and in previous Si-Heusler Ternary is not at 60 degrees.
• The Equal percentage lines (prev. slide) are not parallel with this line and are actually closer to 60 degrees
• While equal percentage lines could be off due to experimental/analytical errors, the boundary can not
8
6
4
2
0
Y P
os [m
m]
86420X Pos [mm]
Sample Boundaries Equalateral Triangle
Si
Mn
Co
Co Zero Line
Possible causes of discrepancy of thicknesses from expected
• Liang says this AA lamps were at the end of their lifetime (each of them) and could cause a systematic error in deposition– Could they cause reduction AND fluctuation?
• Another possibility is the Quartz crystal may have been positioned improperly– would explain a systematic reduction in deposition, but good Mn
agreement on s241 counts against this possibility
• XRF fitting is still very much a black box– I tried fitting the data with different conditions but could find no
conditions that would improve the values– Stefan says as long as fitting procedure same for Standard and Sample,
fitting should be robust
Correlating Results (s230, s239, s241)
• Used XRF data to correlate Binary to Ternary sample
– Right: Blue trace=s239 & Green trace=s230
– Green dot is Si-Heusler
• Expected:– Pleateau of width and zero
in-plane strain in large compositional region, including Heusler
– Brightest spot & narrowest width (best ordering) not at Heusler Stoichiometry
– Best ordering at high Co
• Not Expected:– Heusler sees ~1/4% strain?– 25% Si does not intersect
w/best ordering?4
32
10
Y P
os
[mm
]
6420 X Pos [mm]
80
70
60
50
40
30
L F
WH
M [rlu
] 10
-3
43
21
0Y
Po
s [m
m]
6420 X Pos [mm]
35
30
25
20
15
K F
WH
M [rlu
] 10
-3
43
21
0Y
Po
s [m
m]
6420 X Pos [mm]
1
0.9995
0.9
99
0.999
0.9
98
5
1.001
1.000
0.999
0.998
0.997
0.996
0.995
K-P
ositio
n [rlu
]4
32
10
Y P
os
[mm
]6420 X Pos [mm]
4.02 4.01
4
3.99 3.98
3.97 3.96
3.95
3.94
4.02
4.00
3.98
3.96
3.94
L-P
ositio
n [rlu
]4
32
10
Y P
os
[mm
]
6420 X Pos [mm]
10
8
6
4
2
0
Inte
gra
ted
Inte
nsity 1
0-3
43
21
0Y
Po
s [m
m]
6420 X Pos [mm]
2 1.5
1
0.5
0.3
0.2
2.0
1.5
1.0
0.5
Ph
i FW
HM
[De
g]
• Interpolated s241missing data assuming planar geometry
S239 (Binary) -> s241 (Ternary)• Ternary data sampled at
Binary compositions to compare XRD results
• Intensity traces remarkably similar (factor of ~½ comes from thickness difference)
• L-Positions identical• In-Plane positions have
strange discrepancies below 70% Co, otherwise agree
• In general, width in ternary larger than in binary
– Wider Out-of-Plane due to thickness difference but not much
– Why is Ternary In-Plane wider?
• Phi-direction continues the trend with larger width
• Both grown at 225C• Binary 590A; Ternary 370A• Layers: Binary = CoMnCoSi…
Ternary = CoMnSi…
2
3
456
1
2
3
45
Ph
i FW
HM
[D
eg
]
1009080706050Co Pecent Metal
Phi FWHM s239 s241
0.12
0.10
0.08
0.06
0.04
0.02
Ou
t-o
f-P
lan
e [
rlu
]
1009080706050Co Pecent Metal
40
35
30
25
20
15
10
In-P
lan
e [rlu
] 10
-3
L-FWHM s239 s241K-FWHM s239 s241
4.04
4.02
4.00
3.98
3.96
Ou
t-o
f-P
lan
e [
rlu
]
1009080706050Co Pecent Metal
1.002
1.001
1.000
0.999
0.998
In-P
lan
e [rlu
]
L-Position s239 s241K-Position s239 s241
4
10-4
2
4
10-3
2
4
10-2
2
Inte
gra
ted
In
ten
sity
1009080706050Co Pecent Metal
Intensity s239 s241
S230 (Binary) -> s241 (Ternary)• Intensity traces again similar
This time the Binary is weaker• Intensity peak at ~68% in both
data sets (shows up more if linear scale)
• L-Positions again identical• In-Plane positions agree well
with slight offset from 1 in the ternary (probably diffractometer calibration)
• In general, width in ternary larger than in binary
– Wider Out-of-Plane due to thickness difference but not much
– Why is In-Plane wider?
• Phi-direction continues the trend with larger width. Slightly more discrepancy
2
3
456
1
2
3
45
Phi
FW
HM
[D
eg
]
1009080706050Co Percent Metal
Phi FWHM s230 s241
0.12
0.10
0.08
0.06
0.04
0.02
Ou
t-of
-Pla
ne
[rlu
]
1009080706050Co Percent Metal
40
35
30
25
20
15
10
In-P
lane
[rlu] 10
-3
L-FWHM s230 s241K-FWHM s230 s241
4.04
4.02
4.00
3.98
3.96
Ou
t-of
-Pla
ne
[rlu
]
1009080706050Co Percent Metal
1.002
1.001
1.000
0.999
0.998
In-P
lane
[rlu]
L-Poistion s230 s241K-Position s230 s241
4
10-4
2
4
10-3
2
4
10-2
2
Inte
gra
ted
inte
nsi
ty
1009080706050Co Percent Metal
Intensity s230 s241
• Binary grown at 300C; Ternary 225C• Binary 540A; Ternary 370A• Layers: Binary = CoMnCoSi…
Ternary = CoMnSi…
New General Conclusions
• I would say this shows good reproduction of data and gives us an idea of our error
• There could be a systematic error in composition causing the strain measurements to be off from the Heusler (1% is too far off to be from miscalibration of diffractometer) or there could be some Mn loss into the Ge substrate causing the Heusler comp to shift