CATHODE VOLTAGE GAS-COMPOSITION FILM CRYSTALLOGRAPHY RELATIONSHIPS FOR SPUTTER-DEPOSITED VANADIA (V2O5)

Films were grown by r.f.-excited reactive sputter deposition on opening-elbow-111-closing elbow-cut silicon substrates using a vanadium target and O2-bearing discharges containing 0%-98% argon operated at four values of cathode voltage. The 4111.6-angstrom emission line intensity from neutral excited vanadium atoms in the discharge was monitored by optical spectrometry, and these data were used to detect target surface oxidation. The region of cathode voltage-gas O2 content space over which crystalline vanadia was produced was defined. All crystalline vanadia grew with vanadyl oxygen layers oriented parallel to the substrate (b axis normal). The interlayer spacing b varied from less than to greater than b0, the value for bulk vanadia. An oxidized target surface was a requirement for an interlayer spacing b > b0 but not a guarantee of it. As the cathode voltage decreased, the critical gas O2 content at which the target surface became oxidized was shifted to lower values and the critical gas O2 content at which b > b0 was shifted to higher values, opening up a region in which crystalline vanadia with b less-than-or-equal-to b0 and short-range order vanadia were produced from an oxidized target surface.