MBE GROWTH AND INSTRUMENTATION

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MBE GROWTH AND INSTRUMENTATION

• Thesis Proposal Outline for the Degree of
• Master of Science
• Dr. Roman Stemprok, Major Professor
• Dr. Terry Golding, Supervisor /Committee Member
• Dr. Vijay Vaidyanathan, Committee Member
• Dr. Albert B. Grubbs, Jr., Chair of the
  
• Department Of Engineering technology
• University of North Texas

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MBE GROWTH AND INSTRUMENTATION

• Problem Statement
• Purpose of Research
• Research Question
• Statement of Need
• Research Plan
• Assumptions
• Limitations
• Review of Literature
• Methodology
• Summary
• Timeline
• References

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MBE GROWTH AND INSTRUMENTATION
Problem Statement

• Molecular Beam Epitaxy
• Reflection High Energy Electron Diffraction
  (RHEED)

RHEED Gun setup for MBE growth 1
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MBE GROWTH AND INSTRUMENTATION
Purpose of Research

• MBE source maintenance
• UHV basics and maintenance
• MBE sample loading and preperation
• Operating softwares such as SpecVIEW, Video RHEED
  Intensity Measurement Program, Spectramass 2000
  software.
• Developing a LabVIEW program for the acquisition
  of images and calculating the sample growth rate.
• Using the program to study the growth of GaP
  using atomic phosphorus.

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MBE GROWTH AND INSTRUMENTATION
Research Question

• Identifying and overcoming the various
  limitations during MBE growth process
• To write a LabVIEW program to acquire and analyze
  images using existing devices in the market at a
  minimum cost
• Set up the III/V MBE system for growth of GaP
  samples through the use of a phosphorous cracker

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MBE Growth and Instrumentation/ Statement of Need

• Molecular Beam Epitaxy
• Slow growth rate of 1µm/hr.
• Reduced temperatures. For example about 500-600oC
  for GaAs.
• Reduced handling requirements of toxic materials
  such as As.
• The ability to abruptly cease or initiate
  molecular beams producing hyperabrupt surfaces.
• Facility of in situ analysis during growth.
• Growth of electronic and photonic devices such as
  solar cells, diode lasers, LEDs and bi-polar
  junction transistor.

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MBE Growth and Instrumentation/ Statement of Need

• Electron Diffraction
• Lattice Basis Crystal Structure

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Crystal Structure
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Space
Lattice

Basis, containing two different ions
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MBE Growth and Instrumentation/ Statement of
Need

• Electron DiffractionBraggs Law

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MBE Growth and Instrumentation/ Statement of Need

• Electron diffraction
• The electron density of a crystal can be
  represented in Fourier series in single dimension
  as
• where, n(x) is the electron density and
  is a point in Fourier space or reciprocal
  lattice space, n(x) has a period of a and the sum
  is over all integers p positive, negative and
  zero.

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MBE Growth and Instrumentation / Statement of Need

• Extending the analysis to three dimensional
  lattice structures,
• where is called the reciprocal
  lattice vector and is given by
• where, h,k,l are integers, a, b, c are the
  crystal axes of the original crystal structure
  and A,B,C are the axes for the reciprocal lattice
  space.

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MBE Growth and Instrumentation / Statement of Need

• Ewalds Sphere for construction of diffraction
  pattern in reciprocal lattice space, where,

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MBE Growth and Instrumentation / Statement of Need

• RHEED Patterns

Fig (6.a) RHEED patterns and the corresponding
electron micrographs of GaAs grown using MBE GaAs
heated in vacuum to 580oC for 5min.
RHEED patterns and the corresponding electron
micrographs of Fig (6.a) after 1µm of GaAs
deposited on surface of (6.a).
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MBE Growth and Instrumentation / Statement of Need

• RHEED OSCILLATIONS

Ilustration of RHEED spot oscillations during the
growth of a monolayer 7
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MBE Growth and Instrumentation / Research Plan

• LabVIEW
• Preparing the III/V MBE chamber for the growth of
  GaP crystals using atomic phosphorous cracker.

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MBE Growth and Instrumentation / Research Plan
LabVIEW

• A subVI to store the images.
• A subVI to mesaure the intensity of images at a
  particular region of interest, continuously in
  time.
• A subVI to plot the Intensity vs Time graph of
  the measured intensity.
• A subVI to calculate the growth rate of the
  sample.

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MBE Growth and Instrumentation / Research Plan
Preparing the III/V Chamber

• Cleaning the view ports
  in the ratio of 1210
• Checking the crucibles.
• Clearing the molybdenum blocks
  in a ratio of 121.
• Aligning the linear transfer rod.
• Venting the chamber.
• Degassing and deoxidizing the samples.

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MBE Growth and Instrumentation / Assumptions

• The terms and formulas used will require a basic
  knowledge of mathematics, engineering and
  physics.
• The software implementation will require
  knowledge of LabVIEW, DOS and Windows Operating
  environment.
• The experiments will be carried out based on the
  evidence available through prior research in this
  field. It will be assumed that similar or
  required growth environments have been
  established and the results will be analyzed
  accordingly.
• The system is basically an III/V growth chamber
  and is assumed to work well at different
  temperatures and pressures with the materials not
  used previously within the chamber.
• The LabVIEW program that is to be written is
  assumed to work on the similar guidelines of the
  existing software and yield compatible results.
  The depth and extension of the research mainly
  depends on the timeline and the cost constraints.
• It is assumed that all samples are doped with
  the said percentages of constituent materials.
• The RHEED is assumed to be fully functional as
  per the given specifications.

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MBE Growth and Instrumentation / Limitations

1. This research is limited only to get acquainted
   with the MBE growth process and instrumentation.
2. The proposed LabVIEW program shall be written for
   implementation only with the III/V MBE system.
3. The LabVIEW program is aimed only at displaying
   the intensity vs time graph and calculating the
   growth rate of the sample.
4. The measurements shall be taken on 4-6 samples.
5. The project is bound by the cost ( The frame
   grabber card and the Vision Development module
   cost 2100) and the timeline (6 months)
   constraints.
6. The study shall be concentrated mainly on the
   growth of GaP samples using an atomic phosphorous
   cracker.

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MBE Growth and Instrumentation / Review of
Literature

• Proposed by Gunther in 1958.

Schematic illustration of basic evaporation
process for molecular beam epitaxy .
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MBE Growth and Instrumentation / Review of
Literature
Schematic cross section of an advanced three-
chamber UHV system designed for MBE growth and
detailed surface studies 10.
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MBE Growth and Instrumentation / Methodology
Introduction
Varian 360,
III/V MBE chamber at UNT
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MBE Growth and Instrumentation / Methodology
Load-lock chamber of
the III/V MBE system
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MBE Growth and Instrumentation / Methodology
View port of the load-lock chamber
showing the molybdenum blocks and samples.
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MBE Growth and Instrumentation / Methodology
Preparation
chamber of the III/V MBE system
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MBE Growth and Instrumentation / Methodology
Top view of a typical
standard MBE system growth chamber 13.
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MBE Growth and Instrumentation / Methodology
Growth chamber of
III/V MBE system.
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MBE Growth and Instrumentation / Methodology

• Spectramass PC2000 mass spectrometer software.
• SpecView Plus software.
• Video RHEED Intensity Measurement System, Program
  RHEED.
• Vacuum pumps
• Mechanical pump (2)
• Turbo pump (1)
• Ion pump (3)
• Cryo pump (1)

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MBE Growth and Instrumentation/ Methodology
Vacuum Pumps
Vacuum
pumps on the III/V MBE system
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MBE Growth and Instrumentation / Methodology
Control Equipment
Ion pump control unit housing rack
Furnace control unit housing rack
RHEED control Equipment housing rack
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MBE Growth and Instrumentation / Summary

• Summary of the study.
• Answer to research questions.
• Conclusions based on the results and analysis of
  the study.
• Strengths of the study.
• Weakness of the study.

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MBE Growth and Instrumentation / Timeline
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MBE Growth and Instrumentation / References

1. http//mrlxp2.mrl.uiuc.edu/rheed/index.html
2. Oscillations in the Surface Structure of Sn-doped
   GaAs during growth by MBE Surf. Sci. 103, L90
   (1981) by J.J.Harris, B.A.Joyce and P.J.Dobson.
3. K.G. Gunther, Z.Naturforsch. 13A (1958) 1801 W.
   Hanlein, K.G. Gunther, in Advances in Vaccum
   Science Technology (Proc. 1st Int. Congr. on
   Vacuum Techiques, Namur 1958) 727.
4. J.R.Arthur, J.Appl. Phys. 39 (1968) 4032.
5. C.Kittel, Introduction to Solid State Physics.

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MBE Growth and Instrumentation / References

1. A.Y.Cho, J. Vac. Sci. Technol. 8, S31 (1971).
2. http//www.ece.utexas.edu/projects/ece/mrc/groups/
   street_mbe/mbechapter
3. http//sine.ni.com/apps/we/nioc.vp?cid11407lang
   US
4. Gunther, K.G. 1958. Z. Naturforsch. Teil A
   131801-89.
5. Davey, J.E. Pankey, T. 1968. J. Appl. Phys, 39
   1941-48.
6. Molecular Beam Epitaxy of III-V Compounds
   Technology and Growth Process, by Klaus Proog.
   Ann. Rev. Material Sci. 1981. 11-171-210.

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MBE Growth and Instrumentation / References

1. MBE Varian 360 manual, Operations and Routine
   Maintenance, Varian Industrial Equipment
   Group,1978.
2. W.Braun. Applied RHEED. Reflection High-energy
   Electron Diffraction during Crystal Growth. 1999.
   Springer Tracts in Modern Physics, 154. 2. The
   Spectramass PC 2000 mass spectrometer manual,
   Kurt J.Lesker Co.
3. The Spectramass PC 2000 mass spectrometer manual,
   Kurt J.Lesker Co.
4. Spec View Plus software User Guide, Spec View
   LLC, February 1, 2000.
5. Varian System Instruction manual, Volume 1 2,
   Varian Industrial Equipment Group.

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QUESTIONS????
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Thank you