Growth and Characterization of Zr and ZrC Thin Films on Al2O3(0001)

I report the growth of epitaxial Zr(0 0 0 1) and ZrC(1 1 1) thin films on Al2O3(0 0 0 1) via dc magnetron sputtering in an ultra-high vacuum deposition system equipped with facilities for chemical vapor deposition, low-energy electron diffraction, and Auger electron spectroscopy. Zr layers with a nominal thickness up to 270 nm are deposited at a rate of ∼0.07 nm/s in 10 mTorr Ar (99.999%) atmosphere. ZrC layers with a nominal thickness up to 110 nm are deposited at a rate of ∼0.06 nm/s in 10 mTorr atmosphere composed of 1 mTorr C2H4 (99.999%) and 9 mTorr Ar. As part of my thesis work, I investigate the effect of substrate temperature during sputter-deposition on the composition and crystallinity of the Zr and ZrC films. The as-deposited films are characterized in situ using Auger electron spectroscopy and low energy electron diffraction and ex situ using x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. I deposited Zr thin films at temperatures between 600°C and 900°C. My x-ray diffraction studies reveal that increasing the substrate temperature during sputter-deposition of Zr leads to the growth of polycrystalline hexagonal close-packed structure Zr films. Cross-sectional transmission electron microscopy images reveal columnar growth and the formation of an interfacial layer, whose thickness increased with increasing temperature. Energy dispersive x-ray spectra obtained from this region reveal the presence of both Zr and Al. I attribute the formation of this interfacial layer to plasma-induced substrate decomposition followed by interdiffusion of Al and Zr at the film-substrate interface during sputtering. I deposited ZrC layers at temperatures between 800°C and 1400°C. X-ray diffraction data acquired from my samples indicate that the crystallinity improves with increasing temperature. X-ray photoelectron spectra reveal that all of my films contain excess carbon, whose content decreases with increasing temperature. Based upon my results, I identify optimal growth temperatures for obtaining single-crystalline and epitaxial Zr and ZrC layers.