A presentation on Molecular Beam Epitaxy made by Deepak Rajput. It was presented as a course requirement at the University of Tennessee Space Institute in Fall 2008.
Chemical Vapour Deposition is a Chemical Synthesis route of Nanomaterials. Specially thin films like Graphene and Carbon NanoTubes are grown by this method.
Different types of Nanolithography technique.
Types: Electron beam lithography, Photolithography, electron-beam writing, ion- lithography, X-ray lithography, and related images, concepts and graphical views.
I hope this presentation helpful for you.
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Preeti Choudhary
Electron beam lithography (often abbreviated as e-beam lithography or EBL) is the process of transferring a pattern onto the surface of a substrate by first scanning a thin layer of organic film (called resist) on the surface by a tightly focused and precisely controlled electron beam (exposure) and then selectively removing the exposed or nonexposed regions of the resist in a solvent (developing). The process allows patterning of very small features, often with the dimensions of submicrometer down to a few nanometers, either covering the selected areas of the surface by the resist or exposing otherwise resist-covered areas. The exposed areas could be further processed for etching or thin-film deposition while the covered parts are protected during these processes. The advantage of e-beam lithography stems from the shorter wavelength of accelerated electrons compared to the wavelength of ultraviolet (UV) light used in photolithography.
In EBL, a resist layer is directly patterned by scanning with an electron beam electronically. Modern EBL systems have very good depth of focus (several hundred nanometres) and are able to correct for large-scale height variations of the wafer (of several hundred microns), and so are able to cope well with the rough surface topology of typical GaN wafers and associated wafer bow. EBL also has the advantage of allowing multiple designs to be fabricated together on one wafer. EBL is, however, a slow and expensive process, which is not practical for production. Substrate charging and proximity error effects must be taken into account to get good quality devices. Charging effects can be overcome by application of a sub-nanoscale removable conductive layer on top of the resist. Proximity error correction effects are overcome using specialised design correction software.
If you have any questions, contact me. I would be happy to help.
PLEASE LIKE IT AND GIVE COMMENT
In this presentation,
The author gives the working principle of the PVD and Sputtering methods. But you can also find an information about the thin film and plasma phase of a matter.
Also this is related with Magnetron Sputtering method.
Chemical Vapour Deposition is a Chemical Synthesis route of Nanomaterials. Specially thin films like Graphene and Carbon NanoTubes are grown by this method.
Different types of Nanolithography technique.
Types: Electron beam lithography, Photolithography, electron-beam writing, ion- lithography, X-ray lithography, and related images, concepts and graphical views.
I hope this presentation helpful for you.
https://www.linkedin.com/in/preeti-choudhary-266414182/
https://www.instagram.com/chaudharypreeti1997/
https://www.facebook.com/profile.php?id=100013419194533
https://twitter.com/preetic27018281
Please like, share, comment and follow.
stay connected
If any query then contact:
chaudharypreeti1997@gmail.com
Thanking-You
Preeti Choudhary
Electron beam lithography (often abbreviated as e-beam lithography or EBL) is the process of transferring a pattern onto the surface of a substrate by first scanning a thin layer of organic film (called resist) on the surface by a tightly focused and precisely controlled electron beam (exposure) and then selectively removing the exposed or nonexposed regions of the resist in a solvent (developing). The process allows patterning of very small features, often with the dimensions of submicrometer down to a few nanometers, either covering the selected areas of the surface by the resist or exposing otherwise resist-covered areas. The exposed areas could be further processed for etching or thin-film deposition while the covered parts are protected during these processes. The advantage of e-beam lithography stems from the shorter wavelength of accelerated electrons compared to the wavelength of ultraviolet (UV) light used in photolithography.
In EBL, a resist layer is directly patterned by scanning with an electron beam electronically. Modern EBL systems have very good depth of focus (several hundred nanometres) and are able to correct for large-scale height variations of the wafer (of several hundred microns), and so are able to cope well with the rough surface topology of typical GaN wafers and associated wafer bow. EBL also has the advantage of allowing multiple designs to be fabricated together on one wafer. EBL is, however, a slow and expensive process, which is not practical for production. Substrate charging and proximity error effects must be taken into account to get good quality devices. Charging effects can be overcome by application of a sub-nanoscale removable conductive layer on top of the resist. Proximity error correction effects are overcome using specialised design correction software.
If you have any questions, contact me. I would be happy to help.
PLEASE LIKE IT AND GIVE COMMENT
In this presentation,
The author gives the working principle of the PVD and Sputtering methods. But you can also find an information about the thin film and plasma phase of a matter.
Also this is related with Magnetron Sputtering method.
Have an overview of the most conventionally utilized crystal growth techniques: process, diagrams, advantages, and disadvantages. This is the presentation of my "PV cells and materials" course at the MSc Engg. level.
An alternative to the "big molecules" view of proteins is the "small things" view in which protein have a shape and material properties. This talk is about investigating these properties.
Perovskite: introduction, classification, structure of perovskite, method to synthesis, characterization by XRD and UV- vis spectroscopy , lambert beer's law, material properties and advantage and application.
This presentation was made as a seminar requirement by Deepak Rajput at the University of Tennessee Space Institute, Tullahoma, Tennessee, USA in spring 2010.
Please visit http://drajput.com.
Laser Shock Peening of Bulk Metallic GlassesDeepak Rajput
Final report on Laser Shock Peening of Bulk Metallic Glasses submitted by Deepak Rajput at the University of Tennessee at Knoxville.
This experiment was not so fruitful. Also, there is a mistake in the concept of "overlap". However, this was the first ever attempt on laser shock processing of bulk metallic glasses.
Molybdenum-on-Chromium Dual Coating on SteelDeepak Rajput
A presentation on Molybdenum-on-Chromium Dual Coating on Steel made by Deepak Rajput at the Center for Laser Applications, the University of Tennessee Space Institute.
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A presentation on White Light Upconversion Emissions from Tm3+ + Ho3+ + Yb 3+ Codoped Tellurite and Germanate Glasses on Excitation with 798 nm Radiation made by Deepak Rajput. It was presented as a course requirement at the University of Tennessee Space Institute.
In-situ TEM studies of tribo-induced bonding modification in near-frictionles...Deepak Rajput
A presentation on "In-situ TEM studies of tribo-induced bonding modification in near-frictionless carbon films" made by Deepak Rajput. This presentation was based on "critical review of a paper," in All Things Carbon course offered at the University of Tennessee Space Insitute at Tullahoma in Fall 2009.
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A presentation on Diamond-like Carbon Thin Film with Controlled Zeta Potential for Medical Application made by Deepak Rajput. It was presented as a course requirement at the University of Tennessee Space Institute in Fall 2008.
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A presentation on Polarization Spectroscopy by Deepak Rajput, UT Space Institute, TN, USA.
This presentation was made as a course requirement at the University of Tennessee Space Institute at Tullahoma.
A presentation on Photoacoustic Spectroscopy by Deepak Rajput, UT Space Institute, TN, USA.
This presentation was made as a course requirement at the University of Tennessee Space Institute at Tullahoma.
Laser based coatings and freeform fabrication on graphite. This work was done at the Center for Laser Applications (CLA) at the University of Tennessee Space Institute (UTSI) at Tullahoma.
MSE503 Seminar, Fall 2009, UTSI
Super low friction diamond like carbon films made at the Argonne National Laboratory. This presentation is based on a paper published by Dr. Ali Erdemir (J. Vac. Sci. Technol. A 18(4), Jul/Aug 2000 1987-1992).
This presentation was made as a course requirement in the Department of Materials Science and Engineering, the University of Tennessee Space Institute at Tullahoma in Fall 2009.
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Digital Tools and AI for Teaching Learning and Research
Molecular Beam Epitaxy
1. Molecular Beam Epitaxy
MSE 576 Thin Films
09/26/2008
MSE 576: Thin Films
Deepak Rajput
Graduate Research Assistant
Center for Laser Applications
Materials Science & Engineering
University of Tennessee Space Institute
Tullahoma, Tennessee 37388-9700
Email: drajput@utsi.edu
Web: http://drajput.com
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2. Outline
Epitaxy
MSE 576 Thin Films
Molecular Beam Epitaxy
Molecular Beam
Problems and Diagnostics
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3. Epitaxy
Method of depositing a monocrystalline film.
MSE 576 Thin Films
Greek root: epi means “above” and taxis means “ordered”.
Grown from: gaseous or liquid precursors.
Substrate acts as a seed crystal: film follows that !
Two kinds: Homoepitaxy (same composition) and
Heteroepitaxy (different composition).
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4. Epitaxy
Homoepitaxy:
MSE 576 Thin Films
# To grow more purified films than the substrate.
# To fabricate layers with different doping levels
Heteroepitaxy:
# To grow films of materials of which single crystals
cannot be grown.
# To fabricate integrated crystalline layers of different
materials
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5. Epitaxy
Vapor Phase Epitaxy (VPE)
SiCl4(g) + 2H2(g) ↔ Si(s) + 4HCl(g) (at 12000C)
# VPE growth rate: proportion of the two source gases
MSE 576 Thin Films
Liquid Phase Epitaxy (LPE)
Czochralski method (Si, Ge, GaAs)
# Growing crystals from melt on solid substrates
# Compound semiconductors (ternary and quaternary III-V
compounds on GaAs substrates)
Molecular Beam Epitaxy (MBE)
# Evaporated beam of particles
# Very high vacuum (10-8 Pa); condense on the substrate
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6. Molecular Beam Epitaxy
MSE 576 Thin Films
6 Source: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA xx
6 of
7. Molecular Beam Epitaxy: Idea !
Objective: To deposit single crystal thin films !
MSE 576 Thin Films
Inventors: J.R. Arthur and Alfred Y. Chuo (Bell Labs, 1960)
Very/Ultra high vacuum (10-8 Pa)
Important aspect: slow deposition rate (1 micron/hour)
Slow deposition rates require proportionally better
vacuum.
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8. Molecular Beam Epitaxy: Process
Ultra-pure elements are heated in separate quasi-knudson
effusion cells (e.g., Ga and As) until they begin to slowly
MSE 576 Thin Films
sublimate.
Gaseous elements then condense on the wafer, where
they may react with each other (e.g., GaAs).
The term “beam” means the evaporated atoms do not
interact with each other or with other vacuum chamber
gases until they reach the wafer.
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9. Molecular Beam
A collection of gas molecules moving in the same
direction.
MSE 576 Thin Films
Simplest way to generate: Effusion cell or Knudsen cell
Oven
Orifice Sample
Test Chamber
Pump
9 Knudson cell effusion beam system 9 of xx
10. Molecular beam
Oven contains the material to make the beam.
MSE 576 Thin Films
Oven is connected to a vacuum system through a hole.
The substrate is located with a line-of-sight to the oven
aperture.
From kinetic theory, the flow through the aperture is
simply the molecular impingement rate on the area of
the orifice.
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11. Molecular Beam
Impingement rate is:
1 1 ⎛ p ⎞ ⎛ 8kT ⎞
I = nv = ⎜ ⎟ ⎜ ⎟
4 4 ⎝ kT ⎠ ⎝ πm ⎠
MSE 576 Thin Films
The total flux through the hole will thus be:
pπr 2
Q = IA =
2πmkT
The spatial distribution of molecules from the orifice of
a knudsen cell is normally a cosine distribution:
1 ⎛ cos ϑ ⎞
I ' = nv ⎜ ⎟
4 ⎝ π ⎠
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12. Molecular Beam
The intensity drops off as the square of the distance from the
orifice.
⎛ cos ϑ ⎞⎛ 1 ⎞
I sub = IA⎜ ⎟⎜ 2 ⎟
MSE 576 Thin Films
⎝ π ⎠⎝ L ⎠
or ,
2
⎡ p ⎤⎛ r ⎞
I sub =⎢ ⎥⎜ ⎟ cos ϑ
⎣ 2πmkT ⎦⎝ L ⎠
High velocity, greater probability; the appropriate distribution:
dnv ⎛ v3 ⎞ ⎛ − v2 ⎞
= 2⎜ 4 ⎟ exp⎜ 2 ⎟dv
n ⎜α ⎟ ⎜α ⎟
⎝ ⎠ ⎝ ⎠
12 where α = 2kT / m 12 of xx
13. Molecular Beam
Integrating the equation gives:
Etr = 2kT
MSE 576 Thin Films
as the mean translational energy of the molecules
# Intensity is maximum in the
direction normal to the orifice and
decreases with increasing θ, which
causes problems. θ
Iθ
# Use collimator, a barrier with a
small hole; it intercepts all of the
13 flow except for that traveling towards the sample. 13 of xx
14. MBE: In-situ process diagnostics
RHEED (Reflection High Energy Electron Diffraction)
is used to monitor the growth of the crystal layers.
MSE 576 Thin Films
Computer controlled shutters of each furnace allows
precise control of the thickness of each layer, down to a
single layer of atoms.
Intricate structures of layers of different materials can be
fabricated this way e.g., semiconductor lasers, LEDs.
Systems requiring substrates to be cooled: Cryopumps
and Cryopanels are used using liquid nitrogen.
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15. ATG Instability
Ataro-Tiller-Grinfeld (ATG) Instability: Often
encountered during MBE.
MSE 576 Thin Films
If there is a lattice mismatch between the substrate and
the growing film, elastic energy is accumulated in the
growing film.
At some critical film thickness, the film may break/crack
to lower the free energy of the film.
The critical film thickness depends on the Young’s
moduli, mismatch size, and surface tensions.
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16. Assignment
Solve the equation to find the mean translational energy
(Etr) of the molecules:
⎛ v3 ⎞ ⎛ − v2 ⎞
MSE 576 Thin Films
dnv ⎟dv
= 2⎜ 4 ⎟ exp⎜ 2 ⎟
n ⎜α ⎟ ⎜α
⎝ ⎠ ⎝ ⎠
where α = 2kT / m
What fraction of the molecules in a molecular beam of
N2 formed by effusion of N2 gas initially at 300 K from
an orifice at a large Knudsen number will have kinetic
energies greater than 8kcal/mol?
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