Date of Award

4-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Materials Science and Engineering

Advisor

Dr. Olin Thompson Mefford

Committee Member

Dr. Vincent Blouin

Committee Member

Dr. Stephanie Crette

Committee Member

Dr. Marian Kennedy

Abstract

Sub- and supercritical fluids remain an underexploited resource for materials processing. Around its critical point a common compound such as water behaves like a different substance exhibiting changes in its properties that modify its behavior as a solvent and unlock reaction paths not viable in other conditions. In the subcritical region water’s properties can be directed by controlling temperature and pressure.

Water and silicon are two of the most abundant, versatile, environmentally non-harmful, and simplest substances on Earth. They are among the most researched and best-known substances. Both are ubiquitous and essential for present-day world. Silicon is fundamental in semiconductor fabrication, microelectromechanical systems, and photovoltaic cells. Wet etching of silicon is a fabrication strategy shared by these three applications. Processing of silicon requires large amounts of water, often involving dangerous and environmentally hazardous chemicals. Yet, minimal knowledge is available on the ways high temperature water interacts with crystalline silicon.

The purpose of this project is to identify and implement a method for the modification of monocrystalline silicon surfaces with three important characteristics: 1) requires minimal amounts of added chemicals, 2) controllability of morphological features formed, 3) reduced processing time. This will be accomplished by subjecting crystalline silicon to diluted alkaline solutions working in the subcritical region of water. This approach allows for variations on surface morphologies and etching rates by adapting the reactions conditions, with focus on composition and temperature of the solutions used.

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