Application of picosecond interferometry to characterize physical behavior of crystals

Mahat, Sushant

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https://hdl.handle.net/2142/116158 Copy

Description

Title

Application of picosecond interferometry to characterize physical behavior of crystals

Author(s)

Mahat, Sushant

Issue Date

2022-06-28

Director of Research (if dissertation) or Advisor (if thesis)

Cahill, David G

Doctoral Committee Chair(s)

Cahill, David G

Committee Member(s)

• Schleife, Andre
• Hoffmann, Axel
• Perry, Nicola H

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

elastic, photoelastic, tensors, elastic constants

Abstract

Recent development in computational tools have enabled rapid discovery of new materials with highly specialized properties. In contrast, growth and synthesis processes lag behind significantly in terms of high throughput capabilities. Part of the problem in development of new materials is lack of characterization tools capable of accurately mapping different physical properties in grown materials. Most materials development process remain iterative trail-and-error procedures, requiring repeated rounds of growth and characterization before a material is ready for deployment. Having tools capable of providing composition-process-structure-property relation at each iterative step would significantly reduce the trial-and-error nature of these growth characterization cycles, and would generate a lot of materials data. In this dissertation, I develop and improve the picosecond interferometric technique (PI) tool. PI is an optical pump probe technique capable of non-contact characterization using ultrashort laser pulses. Recently, high throughput characterization of thermal properties was made possible using an optical pump probe technique similar to PI. As the PI technique can simultaneously probe different physical properties, it is a strong candidate for development as a high throughput characterization tool. While the primary use of the PI technique has been to characterize thermal and mechanical properties of newly grown thin films, small adjustments and a through study of the system can allow for characterization of many properties of materials grown in many shapes and forms. In this work, I explore the use of picosecond interferometry technique in characterizing the full set of elastic constants and photoelastic constants of semiconducting crystals. I report how the PI tool can be used to calculate the full set of elastic constants and relative photoelastic constants of crystals. Despite being fundamental materials property, full set of elastic and photo elastic constants are not characterized for a lot of materials. Part of the reason for this has been the stringent sample requirements of existing techniques. I show that the sample requirements for PI experiment are relatively simpler and could be performed in a high throughout manner. I also use PI to measure optical attenuation in semiconductors. The useful signal in a PI experiment is generated by Brillouin scattering. Often, it may be difficult to parse accurate material properties from a PI signal. After careful consideration of material properties involved, and the signal generation and detection mechanism in PI, I develop and implement computational tools that can extract material properties from PI experimental results. Although the experimental examples shown in this work deal with cubic crystals, the processes laid out, and the calculation made available should work with materials of any symmetry.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Sushant Mahat

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