One dimensional metal nanowires grown by physical vapour ...

Max-Planck-Institut für Intelligente Systeme

One dimensional metal nanowire grown by

physical vapor deposition

DSL

D S LÜNN CHICHT ABOR

Gunther Richter

Max Planck Institute for Intelligent Systems

(formerly MPI for Metals Research)

Stuttgart, Germany

MECANO Meeting, Ecole des Mines, Paris

30th October 2012


Acknowledgment

Universität Stuttgart/MPI für Intelligente Systeme

Karla Hillerich Lisa Hofacker Matthias Kolb Matthias Schamel

Carola Schopf Dominic Linsler Christian Kappel Vanessa Dörlich

Friderike Baras Dominic Zug

Horst P. Strunk

Karlsruher Institut für Technologie

Wenting Huang Andreas Sedlmeyr Reiner Mönig

Oliver Kraft


Overview

Motivation

Examples in nature

Artificial metal nanowhisker:

- Microstructure

- Growth

Nucleation site

Incorporation site

- Mechanical properties

- Composites

Summary


Influence of FIB machining?

Motivation

2 µm2 µm

FIB cutting top-down approach

PVD growth bottom-up process

2 µm

Andreas Schneider

for nano structuring


Overview

Motivation

Examples in nature


- Microstructure

- Growth

Nucleation site

Incorporation site


- Composites

Summary


Historical Whisker: hair silver


Whisker 1574

Found in:

Freiberg

Schwarzwald

Kupferberg

Joachimsthal

Kongsberg

AgS_Heizent.wmv

As long as I am talking about silver matte, I should for the sake of the eager reader tell something that is

characteristic of its nature and behaviour. First: When silver matte is cast into an ingot, and while it is still

hot, it can be hammered and shaped as you wish, just like lead. And further: It is possible to cats figures or

coin medals from it which look like vitreous silver.

When you have cast it into funny little decorative figures, lightly cut or scratch them with a knive and hold

them over a gentle charcoal fire until they get hot, whereupon silver will sprout or grow out of them very

delicately just as it grows in the mineral. This is amusing and very pretty to watch. I am telling this so that

anybody who would like to do this for fun and play with it some more should know how it is done.


Old reviews


Whisker 1574

Vorkommen:

Freiberg

Schwarzwald

Kupferberg

Joachimsthal

Kongsberg


Whisker 1574

Vorkommen:

Freiberg

Schwarzwald

Kupferberg

Joachimsthal

Kongsberg


Overview

Motivation

Examples in nature


- Microstructure

- Growth

Nucleation site

Incorporation site


- Composites

Summary


arteficial Whisker

Substrate: Silicon wafer, Tungsten foil + 30 nm Carbon by magnetron sputtering

Growth parameters: UHV (2·10-10 mbar), Metal thermal evaporation, TS ~ 60% TM

Cu growth: TS = 650°C – 700°C, R = 0.05 nm/s

Crystal morphology: needle / prismatic, diameter 20 -200 nm, Length < 300 µm

Isometric Copper islands grown on a clean Silicon surface


Microstructure

No defects as grain boundaries or

dislocations

the metallic whisker are perfect

single crystalline [011] [111]

[101]

a

bc

x

yz

1.0 nm

ab

c

Copper


Nano-whisker tip

x [111]


HRTEM || whisker axis

10 nm

HRTEM investigation:

e-beam axis: - no edge dislocations detectable

- no screw dislocation detectable

- projected side facets flat

- surface oxidized

- no contaminations visible on surface

e-beam || axis: - 6-fold symmetry

- no stacking faults

- misfit dislocations in Ni

- no dislocations in Cu whisker

- Ni/Cu core-shell structure

- Ni grows epitaxial by island growth


Crystal shape

Shape:

- Low indexed {111}, {100} facets for surface

- Low energy Wulff shape dominates geometry


Fe Nanowhisker

Substrate: Mo foil

Temperature: 800°C α-Fe

Surface not defined by low surface energy {110} facet

[001]

[100]

[010]


Overview

Motivation

Examples in nature


- Microstructure

- Growth

Nucleation site

Incorporation site


- Composites

Summary


Mathematical NW lengthening model

Ruth, V & Hirth, J.P., Kinetics of diffusion-controlled whisker growth, J. Chem. Phys. 41, 3139-3149 (1964)

Metal

flux 5 min 120 min 120 min


Substrate surface contribution

0

1000

2000

3000

4000

5000

6000

7000

8000

0,0E+00 2,0E-04 4,0E-04 6,0E-04 8,0E-04 1,0E-03 1,2E-03 1,4E-03

Whisker length [m]

Tim

e [

s]

100200

300400

500600

0

2

4

6

8

10

12

14

5

10

15

20

Beta

Diff

usio

n le

ngth

(µm

)

Whisker radius (nm)

Vl (m/s) w/D (1/m2) ß X (µm)

4,4E-08 6,8E+06 10,6 380

1,3E-08 1,9E+07 57,2 230

2,2E-08 3,0E+07 0,5 180

2,0E-08 7,2E+06 9,2 370

1,8E-07 9,1E+08 0,7 33

Whisker growth:

- NW growth by adatom diffusion on

substrate surface

- direct impingement on whisker facets

- Adatom incorporation: tip or root

Whisker formation:

- nucleation at preferred sites

- transformation from 2D nucleus to 1D

proto-whisker

- predominant growth by adatom

diffusion on substrate surface

- direct impingement on whisker facets

- whisker formation kinetically driven


Substrate-Whisker interface

Si substrate

CuxSi

Ni film

C layer

Ni/Cu whisker

Sabine Haag


C-Film Structuring

Preferred nucleation in C holes


Growth mechanism I

1800

1900

2000

2100

2200

2300

2400

0 10 20 30 40 50Beschichtungszeit t [min]

Länge [nm

]

Sequence of deposition steps:

30 nm C/Si(111)

10 min deposition @ 680°C

SEM analysis

Secondary nucleation on NW side

facets

island growth

No lengthening

deactivation of atom incorporation


50 nm Au colloids deposited by spin coating

Artificial nucleation site

30 nm deposition steps @ 680°C

Lengthening and structure rotation

Incorporation site still active

Growth mechanism II


Growth mechanism III

Fe-Cu-nanowhisker:

1. 180 nm Cu @ 680°C

2. 30 nm Fe @ 680°C

substrate 30 nm/Si(100)

Miscibility gap

TEM grid

Formation of second

phase (Fe rich) at

interface

Nucleation and film

growth on NW surface


Phenomenological growth model

Suitable Substrate:

- Si

- metal surface

Nucleation site:

- Colloids

- Defects in “non-wetting layer”

Metal condensation

Adatom diffusion

Nucleation

Nuclei growth

“Proto-whisker formation”

Nucleation and layer growth

on facets

Thickening

Adatom incorporation at

interface

Lengthening


Overview

Motivation

Examples in nature


- Microstructure

- Growth

Nucleation site

Incorporation site


- Composites

Summary


cyclic in situ bending


0 50 100 150 200 250 3000

2

4

6

8

be

nd

ing

stre

ss (

GP

a)

diameter (nm)

-2 -1 0 1 2 3 4 50

1

2 graphisch bestimmt

berechnet

y-K

oo

rdin

ate

in

m

x-Koordinate in m

Results

0 50 100 150 200 250 3000

1

2

3

4 m=0.47

shea

r st

ress

(GPa

)

diameter (nm)

m=0.41

Mckenzie

Frenkel

Bending stress:

- Lower limit of strength by curvature measurement

- No diameter dependence

Only small dislocation free volumes are tested

(colmpare results from Bei and Pharr)

Shear stress

whisker axis || <110> calculation of shear stress

- Close to predicted value for partial dislocation

(compare talk R. Mönig)


Overview

Motivation

Examples in nature


- Microstructure

- Growth

Nucleation site

Incorporation site


- Composites

Summary


Advanced microstructures: Au-Ag core shell

structures

0 1 2 3 4 5 6

Ag L

Inte

nsity

(a.u

.)

Energy (keV)

Au M

50 nm

10 µm 4 µm 2 µm

A

D E

B C

D E


Au-Ag core shell structures: Annealing

10 µm 1 µm2 µm

A B C

D

Measurement area and

microscope type

IAu Mα/IAg Lα

as deposited

IAu Mα/IAg Lα

after annealing

Film SEM Ag not detectable 11.9

0.5

Whisker SEM 0.4

0.1 12.2

2.8

Whisker TEM 0.5

0.1 13.9

1.3


Au(Ag)-Metallic nano-tubes

2 nm

[100]

[011]

200 nm

022

111

111

-

-

- -

[011]


Tube formation: Model

A B C D

: Substrate and Au grain boundaries : Au: Ag

Ag nano-whisker growth:

- Si(100) substrate

- R = 0.05 nm/s, TS = 800°C

- Cooling to RT



A B C D


Au film deposition:

- TS = RT no interdiffusion

- R = 0.02 nm/s cube-on-cube epitaxy on Ag whisker

polycrystalline Au film on substrate, columnar grains

- grain diameter ~ 100 nm



A B C D


Au(Ag) nano-tube formation:

- TS < 300°C activation of Ag diffusion

- t = 70 h D = 2.7·10-25 m2/s L ~ Å

Dgb = 7.6·10-15 m2/s Lgb ~ µm

- Ag depletion by surface diffusion

H. Mehrer, Ed., Landolt-Börnstein New Series, Group III:

Crystal and Solid State Physics, Volume 26, Diffusion in Solid Metals and Alloys (Springer-Verlag Berlin 1990)



A B C D


Au(Ag) nano-tube:

- wall thickness < 10 nm, length ~ 15 µm

- single crystalline, dislocation free, stacking faults from wall formation

- attached to substrate

- no Kirkendall effect but lost-wax process

H. Mehrer, Ed., Landolt-Börnstein New Series, Group III:

Crystal and Solid State Physics, Volume 26, Diffusion in Solid Metals and Alloys (Springer-Verlag Berlin 1990)


Non Metal Nanowhisker

• Electron beam deposition of NaCl @ 250°C

• Evaporation of Na-Cl dimers

• Substrate: MgO, Al2O3, Ge, W

• Growth direction: <100>

• 2nd material deposition (e.g. V)

Core shell structures without Kirkendall effect


Summary

Nanowhiskers:

- Unique microstructure Wulff-shape

- Root growth Arrays of nanowhiskers by tuning nucleation site

- 3D-substrate Advanced composites

- Unique properties Theoretical mechanical strength limit reached


Acknowledgment

Universität Stuttgart/MPI für Intelligente Systeme

Karla Hillerich Lisa Hofacker Matthias Kolb Matthias Schamel

Carola Schopf Dominic Linsler Christian Kappel Vanessa Dörlich

Friderike Baras Dominic Zug

Horst P. Strunk

Karlsruher Institut für Technologie

Wenting Huang Andreas Sedlmeyr Reiner Mönig

Oliver Kraft

Thank you for your attention!

Date post:	01-Jan-2017
Category:	Documents
Upload:	vothuy
View:	214 times
Download:	0 times

One dimensional metal nanowires grown by physical vapour ...

Documents