Atomic Layer Deposition of Defective Amorphous TiO Thin Films with Improved Photoelectrochemical Performance

A proper control of defects in TiO₂ thin films is challenging work for enhancing the photoelectrochemical (PEC) efficiency in water splitting processes. Additionally, a deep understanding of how defects affect the PEC performance of TiO₂ thin films is of great interest for achieving better performance. With these aims, we prepared defective amorphous TiO thin films at various growth temperatures by atomic layer deposition using tetrakis(dimethylamido)titanium as the Ti precursor. Careful X-ray photoelectron spectroscopy and electron spin resonance spectroscopy analyses revealed that the defect concentration in the TiO thin films can be controlled by adjusting the growth temperature during the ALD process. We also evaluated the light absorption properties of the deposited TiO thin films using ultraviolet-visible absorption spectroscopy. And it was found that the TiO thin film deposited at a growth temperature of 200 °C exhibited the highest defect concentration and the highest photocurrent density of 0.051 mA/cm² at 1.23 V vs reversible hydrogen electrode (RHE) compared to those of the other films. The light absorption efficiency, photogenerated charge separation efficiency, and charge transfer efficiency of defective amorphous TiO thin films were carefully studied to understand the correlation between the defect concentration in the prepared TiO thin film and its PEC activity. This study provides insight into the PEC properties of defective amorphous ALD-TiO thin films.