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Effect of oxygen flow rate on the low temperature deposition of titanium monoxide thin films via electron beam evaporation

Cosar, Mustafa Burak
Icli, Kerem Cagatay
Ozenbas, Macit
In this study, titanium monoxide thin films were evaporated by an electron beam source under different oxygen atmospheres at deposition temperatures not exceeding 80 degrees C. Deposition of thin films at low temperatures is a prerequisite for heat sensitive substrates. XRD results showed that crystallinity of titanium monoxide is achieved without the requirement of high temperature annealing. When oxygen is introduced into the coating chamber, a titanium peak is formed at exactly the Ti+2 position together with a small amount of Ti+3 and Ti+4 peaks. According to XPS analysis, the structure is transformed into mostly the Ti+4 state when the oxygen flow rate is over 25 sccm. The bandgap of thin films increases from 3.0 to 3.8 eV with an increase in oxygen flow rate from 1 to 50 sccm. Both optical transmission and Hall effect measurements showed the change in carrier type from p to n when the flow rate reaches 25 sccm. Electrical resistivity increases with additional oxygen in the structure, and minimum resistivity is obtained as 1.7 x 10(-4) Omega cm when no oxygen is admitted into the chamber. Highly conductive thin films were also observed via ultraviolet photoelectron spectroscopy measurements which yield a high density state showing a metallic character with degenerated oxide semiconductor nature. Published by the AVS.