MOCVD Route to Stable, Oxygen-Rich, Chromium Oxide Films and Their Conversion to Epitaxial Cr2O3

Abstract

Using Cr(acac){sub 3} as a precursor, deposition of chromium oxide onto silicon and Al{sub 2}O{sub 3} by MOCVD produced 800 {angstrom} to 2 {mu}m thick films, which were characterized by IR, UV-vis spectroscopies, XPS, oxygen and carbon resonance RBS, and XRD, as well as optical and electron microscopies. Optimization of deposition conditions such as precursor temperature, carrier gas type and flow rate, substrate type and temperature, and postdeposition anneal yielded smooth, crystalline, epitaxially oriented films of Cr{sub 2}O{sub 3} on single crystalline Al{sub 2}O{sub 3} substrates. Deposition under flowing O{sub 2} at 400-900{degrees}C produced discontinuous Cr{sub 2}O{sub 3} films comprised of 1-20 {mu}m diameter crystallites the orientation of which was dependent on the substrate. Deposition at 300-350{degrees}C under O{sub 2} and at 300-500{degrees}C under N{sub 2} produced very smooth films of Cr{sub 2}O{sub x} (3.2 {le} x {le} 4.9); such films contained some crystalline Cr{sub 2}O{sub 3}. XPS analysis of these oxygen-rich films revealed the presence of chromium in oxidation states, III (major), IV, and VI. The Cr{sub 2}O{sub 3.5} films did not lose oxygen upon firing to 1100{degrees}C under argon, but were cleanly converted to smooth, epitaxial Cr{sub 2}O{sub 3} at 1300{degrees}C. 47 refs., 6 figs., 1 tab.