Solid-state spreading of oxides: Morphology and conductivity of In2O3-based films

Spontaneous solid-state spreading of In₂O₃ over the surface of ceramic and single crystal substrates of Al₂O₃, ZrO₂(0.08Y₂O₃), Y₃Al₅O₁₂ and YAlO₃ at 1380 and 1500 °C has been investigated. The films structure, element and phase composition were studied by means of XRD and SEM/EDS. The phase compositions of all films correspond to that of powder In₂O₃. The most films are dense with monolithic “film/substrate” interface. AC-conductivity in the range 25–250 °C is reported. Depending on the substrate material, the films demonstrate a whole set of conductivity types (semi-conductive, metallic) and wide range of magnitudes (more than 3 orders).Thermodynamic and kinetic aspects of oxide spreading and subsequent crystallization on the surface of primary border film are discussed. It is shown, in particular, that the solid-state spreading is facilitated in systems with high chemical affinity (mutual solubility, formation of intermediate interface compounds). In the case of eutectic-type systems, heteroepitaxy of diffusant at substrate surface results in formation of dense films.