Robert W. Springer

The organometallic chemical vapor deposition of transition metal carbides: The use of homoleptic alkyls

The organometallic chemical vapor deposition of transition metal carbides (M = Ti, Zr, Hf, and Cr) from tetraneopentyl-metal precursors has been carried out. Metal carbides can be deposited on Si, Al{sub 2}O{sub 3}, and stainless steel substrates from M[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} at temperatures in the range of 300 to 750 C and pressures from 10{sup {minus}2} to 10{sup {minus}4} Torr. Thin films have also been grown using a carrier gas (Ar, H{sub 2}). The effects of variation of the metal center, deposition conditions, and reactor design on the resulting material have been examined by SEM, XPS, XRD, ERD and AES. Hydrocarbon fragments generated in the deposition chamber have been studied in by in-situ mass spectrometry. Complementary studies examining the UHV surface decomposition of Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} have allowed for a better understanding of the mechanism leading to film growth.

Low-Temperature Deposition of ZrC thin films from a Single-Source Precursor

Stable zirconium carbide thin films have been deposited from a single source organometallic precursor, tetraneopentyl zirconium, at substrate temperatures above 500C. Materials deposited above this temperature are crystalline by X-ray diffraction. A metal to carbon ratio of 1:2 is observed by Auger electron spectroscopy depth profiling. X-ray photoelectron spectroscopy indicates the zirconium is single phase. The observed spectra correspond well to spectra for zirconium carbide standards. Carbon XPS reveals carbidic and graphitic or hydrocarbon species with a third unknown carbon species. Elastic recoil detection finds a large, up to 16%, hydrogen content in the thin film.

Investigation of the nucleation and growth of thin-film phosphors

The deposition of CaGa{sub 2}S{sub 4}:Ce has been accomplished using a commercial liquid delivery system on two substrate surfaces: ZnS and SrS. However, the film deposited on ZnS was not of satisfactory quality because of the formation of an amorphous layer and a high amount of residual porosity within the deposition. The use of a SrS layer on top of the ZnS improved the nucleation by reducing the interfacial energy between the substrate and deposition. It greatly reduced the porosity in the coating and reduced the formation of the amorphous layer. The crystallinity of the CaGa{sub 2}S{sub 4} 400 peak was also increased by a factor of ten when a layer of SrS was used. Further, the FWHM of the 400 peaks from the two depositions was not significantly different, indicating that the crystallite size and strain was approximately the same. The B{sub 40} was increased by a factor of two, from 1.84 cd/m{sup 2} for ZnS to 3.67 cd/m{sup 2} for SrS. This increase is an improvement in the performance of the films and is attributable to the increase in the crystallinity.