Formation of titanium oxide phases in vacuum condensates produced by laser evaporation

Abstract

Titanium oxide vacuum condensates are produced by laser evaporation in vacuum, which involves vapor condensation onto a polycrystalline molybdenum substrate heated between 200 and 1500°C. The phases formed in titanium oxide vacuum condensates and their microstructure are studied with x-ray and electron diffraction and transmission electron microscopy. It is established that the phases formed in titanium oxide vacuum condensates are determined by substrate temperature (T s): amorphous TiO2 forms at T s < 400°C, anatase crystallizes at higher T s and coexists with rutile at T s = 700–900°C, and rutile alone is observed at T s > 900°C. Laser evaporation at T s < 1400°C promotes oxygen-rich TiO2 phases and that at T s ≥ 1400°C leads to Magneli phases in titanium oxide vacuum condensates. Higher T s results in phases in which the titanium–oxygen atomic ratio does not correspond to the TiO2 formula. It is shown that variation in the substrate temperature and the size of crystallites in titanium oxide vacuum condensates is symbate.