MOCVD ROUTE TO STABLE, OXYGEN-RICH, CHROMIUM-OXIDE FILMS AND THEIR CONVERSION TO EPITAXIAL CR2O3

Using Cr(acac)3 as a precursor, deposition of chromium oxide onto silicon and Al2O3 by MOCVD produced 800 angstrom to 2 mum thick films, which were characterized by IR, UV-vis spectroscopies, YPS, 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 Cr2O3 on single crystalline Al2O3 substrates. Deposition under flowing 02 at 400-900-degrees-C produced discontinuous Cr2O3 filMS comprised of 1-20 mum diameter crystallites the orientation of which was dependent on the substrate. Deposition at 300-350-degrees-C under 02 and at 300-500-degrees-C under N2 produced very smooth films of Cr2Ox (3.2 less-than-or-equal-to x less-than-or-equal-to 4.9); such films contained some crystalline Cr2O3. XPS analysis of these oxygen-rich films revealed the presence of chromium in oxidation states, III (major), IV, and VI. The Cr2O3.5 films did not lose oxygen upon firing to 1100-degrees-C under argon, but were cleanly converted to smooth, epitaxial Cr2O3 at 1300-degrees-C.