Electrical and optical properties of titanium oxynitride thin films

A TiNxOy (TiNO) material system has been synthesized in thin film form for the first time using a pulsed laser deposition process. X-ray diffraction and X-ray photoelectron spectroscopy measurements have been carried out to show partial oxidation of TiN to TiNO. The current (I)-voltage (V) characteristics recorded from TiNO films sandwiched between indium tin oxide (ITO) and gold (Au) layers and/or copper (Cu) electrodes have shown that the I-V curves lie in the first and third quadrants (i.e., both I and V are either positive or negative) in the dark conditions, while the I-V curves lie in the second and fourth quadrants (i.e., I and V with opposite sign) in the illuminated conditions. The positive sign of power (I x V = Positive) under dark conditions indicates dissipation of power in the TiNO system, while the negative sign of the power (I x V = Negative) under optical illumination indicates the power generation capability of TiNO system. The bandgap of the TiNO thin film samples, measured using ultra violet (UV)-visible (400-800 nm) spectroscopy, was found to be ~ 1.6 eV. As the number of photocatalysts/semiconductors that are active under the visible light irradiation is very limited, our approach to develop a unique visible-light-driven TiNO photoactive material system can open a new avenue for the realization of novel optical devices.