Influence of two gradual steps of vacuum annealing on structural and opto-electronic characteristics of Nb-doped TiO2 transparent conducting oxide

In this research, experimental characterizations of Nb doped TiO2 (TNO) thin films as a transparent conductive oxide (TCO) were reported, with a focus on effects of gradual vacuum annealing (two steps of annealing in different vacuum) was reported. The morphological, optical and electrical characterizations properties of the final thin films confirm the undesired effects of non-gradual vacuum annealing (two steps of annealing in a same vacuum) which can be related to the oxygen vacancy shock in this type of heat treatment. It was has been shown that non-gradual vacuum annealing could act as an obstacle of nucleation and crystallization in thin films preparation. In addition, influences of gradual vacuum annealing on opto-electronic properties of TNO were investigated. It was has been confirmed that oxygen in annealing process plays an important role on optical transparency and electrical conductivity of TNO thin films, so that gradual vacuum annealing could gives TNO thin films a chance at having a better nucleation and more desired crystallites. Sample with gradual vacuum annealing exhibited the resistivity of 0.92 Ω cm and the transparency of about 57% in the visible region spectrum.