Large Photoresponsivity in the Amorphous‐TiO2/SrRuO3 Heterostructure

Abstract

Thin‐film heterostructures are effective in enhancing the performance or triggering novel physical phenomena of optoelectronic applications. For example, the epitaxial heterostructures of ultraviolet‐light‐sensitive TiO2 with metallic SrRuO3 can acquire visible‐light functionalities using the hot carrier injection mechanism. Therefore, the TiO2/SrRuO3 heterostructure system has recently attracted increasing interest. Herein, the amorphous‐TiO2/SrRuO3 heterostructure is fabricated and compared to the epitaxial TiO2/SrRuO3. As opposed to the occurrence of the visible‐light photovoltaic effect in the epitaxial TiO2/SrRuO3, the amorphous‐TiO2/SrRuO3 heterostructure herein exhibits different optoelectronic functionality, specifically the photoresistor behavior. The amorphous‐TiO2/SrRuO3 heterostructure achieves a photoresponsivity of 6.56 A W−1 at 1 V. Such a performance is hardly obtained in typical oxide‐based photoresistors. The analyses of the crystalline and electronic structures show that it is due to the defect‐induced high electron doping in the amorphous TiO2 with hot carrier injection mechanism. This study discusses the correlation between the hot carrier injection and band diagram, which provides more degrees of freedom in designing potential optoelectronic devices.