The effect of Ta doping in polycrystalline TiO_x and the associated thin film transistor properties

Tantalum (Ta) is suggested to act as an electron donor and crystal phase stabilizer in titanium oxide (TiO_x). A transition occurs from an amorphous state to a crystalline phase at an annealing temperature above 300°C in a vacuum ambient. As the annealing temperature increases from 300°C to 450°C, the mobility increases drastically from 0.07 cm ²/Vs to 0.61 cm²/Vs. The remarkable enhancement of thin film transistor performance is suggested to be due to the splitting of Ti 3d band orbitals as well as the increase in Ta⁵⁺ ions that can act as electron donors.