[PPT] - Cdiz Determina nati tion o n of Bi positi tions ns in GaA aAs PowerPoint Presentation

SLIDE 1

Determina nati tion o n of Bi positi tions ns in GaA aAs(1-x)Bi Bix heterost stru ructure res w s with at atomi mic co column r res esolution David d L. S . Sal ales es

(david id.sa .sale les@uc s@uca.e .es) s)

Cádiz

Universidad de

E. Guerre

rrero ro , , J.

J. F.

. Rodrigo, A.

A. Yá

Yáñez, P.

P. L. G

. Galindo, S. I

S. I.

. Molina M. . Henini, M M. . Sh Shafi, S.V S.V. N . Novikov M.F. Ch Chis isholm lm

SLIDE 2

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Framework

7/17/2010

Introduction

Materials Science & Engineering Group
Computational Intelligence systems

STEM Group (Dr. Pennycook’s group)

Dr. Henini’s Group

Workshop on Bi-Containing Semiconductors | David L. Sales | 2 | 30

SLIDE 3

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Transmission electron microscopes

JEOL 2010 FEG JEOL 2011 LaB6 JEOL 1200 EX VG-HB603 VG-HB501 NION UltraSTEM

17/07/2010

Introduction

Aberration-corrected Workshop on Bi-Containing Semiconductors | David L. Sales | 3 | 30

SLIDE 4

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Previous TEM work in GaAsBi

Molecular beam epitaxy of GaAsBi
n (311)B GaAs substrates

17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 4 | 30 GaAs GaAsBi GaAs GaAsBi (b) (c) Z-contrast 1 µm 1 µm (001) (311)B

Introduction

M. Henini et al. Appl. Phys. Lett. 91, 251909 2007

SLIDE 5

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Previous TEM work in GaAsBi

17/07/2010

J. F. Rodrigo et al. Applied Surface Science 256 (2010) 5688–5690

Introduction

Workshop on Bi-Containing Semiconductors | David L. Sales | 5 | 30

SLIDE 6

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Other nano-tools

Focussed Ion Beam

7/17/2010

Nano-machinning
3D sample preparation for tomopraphy
f localized areas.
Substrates nano-patterning
As ions imaging
3D tomography

FEI DUAL BEAM FEI QUANTA 200 3D

Introduction

Workshop on Bi-Containing Semiconductors | David L. Sales | 6 | 30

SLIDE 7 17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 7 | 67

SLIDE 8 17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 8 | 67

SLIDE 9

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

The Motivation

Bi Nanoclusters would explain PL enhancement There are some experimental evidences So… ¿can we see them?

7/17/2010

Introduction

Workshop on Bi-Containing Semiconductors | David L. Sales | 9 | 30

SLIDE 10

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Methodology and materials

17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 10 | 30

SLIDE 11

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Experimental techniques

17/07/2010

Methodology & Materials

A B C A B B B C Workshop on Bi-Containing Semiconductors | David L. Sales | 11 | 30

SLIDE 12

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

The sample

17/07/2010

Methodology & Materials

GaBixAs(1-x) GaAs Substrate semi-insulating (100)

1 µm [001] pAs = 8.0·10-6 Torr T ≈ 350ºC pBi = 1.2·10-7 Torr Region of near stochiometric growth HRXRD x ≈ 0.03 Henini et al. APL 91, 251909 (2007) Workshop on Bi-Containing Semiconductors | David L. Sales | 12 | 30

SLIDE 13

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Why HAADF?

17/07/2010 PhD Defence David Sales Lérida | 13 | 67

Methodology & Materials

SLIDE 14

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Why HAADF?

For a ternary alloy:

– Linear relationship

Intensity quotient (R) vs. Composition.

7/17/2010

x x Re 229 . 1.005 ) ( + =

Column-by-column compositional mapping by Z-contrast imaging

S. I. Molina et al. Ultramicroscopy 109 (2009) 172–176

Methodology & Materials

Workshop on Bi-Containing Semiconductors | David L. Sales | 14 | 30

SLIDE 15

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Quantitative Compositional analysis

17/07/2010 2 nm 2 nm InP InP S25 InP InP 2 nm 2 nm S27 S27 S25 2 4 6 8 10 12 14

0.2

0.0 0.2 0.4 0.6 0.8 1.0 Contenido en P Monocapa 0,2 0,4 0,6 0,8 1,0 P molar fraction, (1-x)

HAADF EELS Methodology & Materials

S27 Workshop on Bi-Containing Semiconductors | David L. Sales | 15 | 30

SLIDE 16

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

STEM - HAADF

17/07/2010 GaAsBi GaAs vacuum

Methodology & Materials

Workshop on Bi-Containing Semiconductors | David L. Sales | 16 | 30

SLIDE 17 Ga As/Bi

SLIDE 18 1. Localize intensity maxima (As/Bi columns) 2. Localize Ga columns 3. Select integration area 4. Determine average integrated intensity in every dumbbell: IGa and IAs/Bi

IGa &IAs/Bi

SLIDE 19

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Image processing

Determining R factors:

17/07/2010

IAs/Bi = R(x) IGa

Minimize variations due to:

Same local thickness
Same amorphous layer
Same experimental image conditions

Methodology & Materials

Workshop on Bi-Containing Semiconductors | David L. Sales | 19 | 30

SLIDE 20

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 20 | 67

SLIDE 21

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Plotting R

17/07/2010

Results

Workshop on Bi-Containing Semiconductors | David L. Sales | 21 | 30

SLIDE 22

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Analysis

In order to relate R with x (Bi content):
Fitting equation:

17/07/2010

Results

∑ ∑

= =

+ =

N i i N i i

x a N R

1 1

N, the number of atomic columns, xi = Bi percentage per column, Σxi=2.65% total Bi percentage

x R 0729 . 0629 . 1 + =

Workshop on Bi-Containing Semiconductors | David L. Sales | 22 | 30

SLIDE 23

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Results

17/07/2010 1 2 3 4

20 40 60 80 100 120 1 2 3 4 Columns Bi atoms per column

Results

Workshop on Bi-Containing Semiconductors | David L. Sales | 23 | 30

SLIDE 24

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

The next step…

STEM image simulations

17/07/2010

] ˆ [ 2

2

= Ψ − + Ψ ∆ V E m

t



Solving the Schrödinger stationary equation by FFT multislice method (Ishizuka’s code) Image Simulations

Workshop on Bi-Containing Semiconductors | David L. Sales | 24 | 30

SLIDE 25

The SICSTEM software

A Paralell HAADF-STEM Simulation Sw

Workshop on Bi-Containing Semiconductors | David L. Sales | 25 | 30

SLIDE 26

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Cádiz University supercomputer

Hewlett-Packard (2007)

– 320 Xeon Woodcrest cores running at 3GHz – 3.75 Tflops (position 327 in Top500 last year) – Each node 8 or 16 Gb RAM – Total RAM = 700 GB – 2.5 TB disk capacity

SLIDE 27

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

Create the supercell

56,000 atoms
5x6x40 nm

17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 27 | 30

Image Simulations

SLIDE 28

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results
Aprox. time for simulation: 50 hours.
High resolution: 182 pix/nm

17/07/2010 Workshop on Bi-Containing Semiconductors | David L. Sales | 28 | 30

Image Simulations

SLIDE 29

I. Introduction
II. Methodology &

Materials

V. Image simulation
Framework
Tools
Previous

GaAsBi works

Motivation
Growth
HAADF
Image

processing

Results

17/07/2010

GaAsBi 40 nm - 3 Bi Atoms in red

Workshop on Bi-Containing Semiconductors | David L. Sales | 29 | 30

Image Simulations

SLIDE 30 Workshop on Bi-Containing Semiconductors | David L. Sales | 30 | 30

Summary and Conclusions

Aberration corrected STEM Character ization TEM Simulation Using HAADF-STEM images, a quantitative composition analysis with atomic column resolution is achievable in GaBiAs layers. In order to corroborate the results and know the limits of this technique, image simulation is being processed using SIC- STEM software.

SLIDE 31

¡Muchas gracias!

Cádiz old town.