Transcript Atif Alam Khan

A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Nanoscale and Atom-scale Characterization of
Novel Functional Nanostructures for
Photonics and Photovoltaics
Atif Alam Khan
ESR Cádiz
INNANOMAT GROUP (MATERIALS and NANOTECHNOLOGY for INNOVATION)
Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, IMEYMAT
Faculty of Science
University of Cádiz
11510 Puerto Real, Cádiz, Spain.
Date: December 8, 2016
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Outline
I. Personal Background
II. The Project
III.Project Background
IV.Methodology and Instrumentation
V. Present Results and Analysis
VI. Summary
VII.Future Works
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Personal Background
• MSc. in Micro- and
Nanotechnology
• Research on
Microphotolumincesce
of Nanostructures
• BSc. in Electrical and
Electronic Engineering
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
The Project
Process Flow
Aims
Materials for Energy (CPV): WP3
Identification of optimum design
parameters for antimony (Sb) based
energy saving high efficient midinfrared (MIR) III-V solar cells (SCs),
light emitting diodes (LEDs) and gas
sensors (GSs) using various
transmission electron microscopy
(TEM) techniques.
Motivation
• 3.6 million GWh electric usage by 2020
• High efficient SC
• Cheaper III-V photonic materials
Solutions
• III-Sb quantum dot (QD) IBSC and LEDs
• III-Sb/Si hybrid tandem structures
Optimization
Modelling
Morphological and
Compositional
analyses
CPV: Concentrated Photovoltaics
IBSC: Intermediate Band Solar Cell
Characterization
Growth
TEM
Processing
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Project Background
QRs: Quantum Rings
Materials
QD formation
wetting layer
dependent
Low QD
density
GaSb QRs for
SCs
GaAs
Differences in lattice
constants and thermal
expansion coefficients
Functionality
barrier layer
dependent: AlSb
TEM
Structural quality
and dimensions
GaxIn1-xAs/III-Sb
for SCs/GSs
Si
AlSb/GaSb
InxAl1-xAsySb1-y
for SCs/GSs
(Al)GaSb
InAs
InSb submonolayer QDs
for LEDS
Barrier based
influences
QRs shapes, density
and dimensions control
device performace
Analyses
Defect type
and density
Compositional
distribution
Designing high efficient
MIR photonic devices
A Marie Skłodowska-Curie Initial
Training Network
Methodology and Instrumentation
JEOL
2010F
JEOL
2100
CTEM: Diffraction
contrast based
morphological
analysis
InSb QDs
InxAl1-xAsySb1-y
HRTEM: Cross-sectional
measurements of nanostructures
Double Aberration Corrected
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
HAADF-STEM: Atomic level
compositional mapping
EDX: Material identification
EELS: Material identification
at nano-scale
GaxIn1-xAs
GaSb QRs
FEI Titan
Cubed
Themis
CTEM: Conventional TEM
HRTEM: High Resolution TEM
HAADF-STEM: High Angle Annular Dark Field-Scanning TEM
EDX: Energy –dispersive X-ray
EELS: Electron Energy Loss Spectroscopy
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Present Results and Analysis: GaSb/GaAs QRs
DIFFRACTION CONTRAST
GaSb QR
• Low QR density (0.004-0.02/nm)
GaSb WL
GaSb WL
• Large barrier prevents vertical stacking
GaAs
• No structural defect/dislocation
GaAs
GaSb QR
• QR induced strain observed
220 bright field image
002 dark field image
HAADF-STEM
nanocup
HAADF-STEM image
• Average QR diameter = 25±3 nm
• Average lobe diameter = 5±2 nm
• Average lobe height = ~ 3 nm
QR
•HAADF images show that the QRs
have the shape of nanocups
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Present Results and Analysis: InSb/InAs QDs
DIFFRACTION CONTRAST
InAs (200 nm)
InSb QDs layers
InAs (200 nm)
• The diffraction contrast images ensure
the presence of 10 InSb QDs layers with
good quality.
InAs (100 nm)
002DF
220BF
InAs (100 nm)
CTEM images
HAADF-STEM
Intensity profiles from
column 10 of the
HAADF-STEM image
InAs
InSb
HAADF-STEM image
of a QD layer region
InAs
Group III
In: Z-> 49
As: Z-> 33
•HAADF images are sensitive to the
average Z number in the atomic columns.
•A new methodology based in HAADF
experimental images and simulations is in
progress in order to quantify the Sb
distribution at atomic column resolution.
•This will allow analyzing the QDs
characteristics, in order to be correlated to
their functional properties.
In
In Sb
As
Group V
Sb: Z-> 51
Simulated intensity profile at
ideal case
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Present Results and Analysis: InSb/(Al)GaSb QDs
DIFFRACTION CONTRAST
QDs layers
•The analysis by diffraction contrast
shows that the InSb/(Al)GaSb QDs layers
have good structural quality.
ATOM PROBE TOMOGRAPHY
220BF
002DF
CTEM images
HAADF-STEM
•In this case, the
existence of more
than one group III
elements complicate
the correlation
intensitycomposition from
HAADF images.
HAADF-STEM image
of a QD layer region
• Atom probe tomography (APT) analysis is in
progress in order to obtain 3-dimensional (3D)
information on the composition distribution of
the material.
• First analyses failed because of the
difficulties in specimen preparation by focused
ion beam (FIB) of Sb containing materials. The
optimization of the preparation process is in
progress.
Scanning Electron
Microscope (SEM) image
of a FIB micro-needle
sample for APT
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Summary
• GaSb/GaAs QRs: the analysis by diffraction contrast shows low QR density of 0.0040.02/nm with no vertical stacking in the SC structure, with an overall good structural
quality. The QRs have “nanocup” shape with an average diameter of ~ 25 nm. These
shape and dimension based information will help finding high optical quality associated
design parameters from fabrication point of view.
• InSb/InAs QDs: the development of a new methodology based in HAADF-STEM
experimental images and simulations is in progress in order to quantify the Sb
distribution at atomic column scale, what will allow the study of the QDs size and shape.
• InSb/(Al)GaSb QDs: the analysis by diffraction contrast ensures a good structural
quality. APT analysis are in progress in order to obtain 3D compositional information
from the material, and for this the optimization of the sample preparation by FIB is being
carried out.
•
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Skills acquired
• Operating JEOL 2100 microscope to do diffraction contrast.
• Interpretation of diffraction contrast images
• Interpretation of HAADF-STEM images with qHAADF and MATLAB software
• Conventional electron transparent TEM sample preparation techniques
Outputs
• Poster presentation in European Microscopy Conference (EMC) in Lyon,
France in August, 2016.
• Poster presentation in Molecular Beam Epitaxy (MBE) conference in
Montpellier, France in September, 2016.
A Marie Skłodowska-Curie Initial
Training Network
Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics
Future Works
• Analysis of InSb/InAs QDs using HAADF-STEM experimental images
and MATLAB simulated data to obtain Sb composition, followed by low
loss EELS experimentation for comparative analysis
• Analysis of InSb/(Al)GaSb QDs samples by APT to determine In
composition and hence, generating complete compositional map
• Analysis of InxAl1-xAsySb1-y quaternary alloy with the help of qHAADF
software and MATLAB simulations
• Analysis on GaxIn1-xAs/III-Sb/Si samples
• Involvement in various outreach programs
• Set up a robust network platfrom that should help me advancing my
career as a future expert either in industry or academy.
Daniel Fernández de los Reyes
Cádiz
12 12