Degree Type

Thesis

Date of Award

2008

Degree Name

Master of Science

Department

Electrical and Computer Engineering

First Advisor

Vikram L. Dalal

Second Advisor

Gary Tuttle

Third Advisor

Mani Mina

Abstract

The benefits of low pressure Plasma Enhanced Chemical Vapor Deposition (PECVD) using helium as the dilutant gas were investigated in a variety of conditions to identify the techniques feasibility as a low band gap material yielding deposition method. Films and photovoltaic devices with intrinsic layers processed at lower pressures with helium dilution are thought to possess improved characteristics with lower hydrogen content and lowered optical band gaps. When films are grown at lower pressures in the presence of helium the optical band gap tends to decrease. Amorphous silicon a-Si:H generally has a band gap around 1.75eV. This work intends to decrease this band gap as far as possible.;Films grown under these conditions exhibited reasonable growth rates considering the conditions and yielded very good photo and dark conductivity. It was expected that dilution with helium at low pressure would decrease hydrogen content by increasing ion bombardment. This was confirmed by FTIR results that indicated hydrogen content of 7-9%. Both films and devices were fabricated that achieved optical band gaps around 1.62-1.65eV. Devices exhibited Urbach energies that were typically lower than 50meV indicating a good quality amorphous structure.

DOI

https://doi.org/10.31274/rtd-180813-16083

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Michael William Beckman

Language

en

Proquest ID

AAI1453075

OCLC Number

237183164

ISBN

9780549541165

File Format

application/pdf

File Size

64 pages

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