On the phase formation of titanium oxide thin films deposited by reactive DC magnetron sputtering: influence of oxygen partial pressure and nitrogen doping

Abstract

This work describes about the control on phase formation in titanium oxide thin films deposited by reactive dc magnetron sputtering. Various phases of titanium oxide thin films were deposited by controlling the oxygen partial pressure during the sputtering process. By adding nitrogen gas to sputter gas mixture of oxygen and argon, the oxygen partial pressure was decreased further below the usual critical value, below and above which the sputtering yields metallic and oxide films, respectively. Furthermore, nitrogen addition eliminated the typical hysteretic behaviour between the flow rate and oxygen partial pressure, and significantly influenced the sputter rate. On increasing the oxygen partial pressure, the ratio between anatase and rutile fraction and grain size increases. The fracture cross-sectional scanning electron microscopy together with the complementary information from X-ray diffraction and micro-Raman investigations revealed the evolution and spatial distribution of the anatase and rutile phases. Both the energy delivered to the growing film and oxygen vacancy concentrations are correlated with the formation of various phases upon varying the oxygen partial pressure.