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The defect structure of VO x . II. Local ionic arrangements in the disordered phase

1979; International Union of Crystallography; Volume: 35; Issue: 6 Linguagem: Inglês

10.1107/s0567739479002175

1600-8596

M. Morinaga, Jerome B. Cohen,

Semiconductor materials and devices

In VOx (0.8 < x < 1.3), there are large numbers of cation and anion vacancies and interstitial vanadium ions. To determine the local arrangements of these defects, X-ray diffuse scattering was measured in absolute units with single crystals of VOx (x = 0.89, 1.17 and 1.28). For x > 1, the interstitials are present near vacancy clusters, similar to the defect arrays found in the semiconductor FexO. For x < 1, there are few interstitials, but an increased concentration of anion vacancies. The anion and cation vacancies are arranged (so as to minimize the electrostatic energy) in rows along (110) directions with alternating vacancy-rich and vacancy-deficient { 111 } layers. Some portions of this vacancy arrangement resemble that found in metallic TiOx. VOx behaves like a semimetal for x < 1, but a semiconductor for x > 1, and the present results, when compared to the defect structures in TiOx and FexO, show that the nature of the bonding between cations and anions controlling the conduction mechanism is reflected in the defect structure.