Tunable Bi-directional Photoresponse in Hybrid PtSe2-x Thin Films Based on Precisely Controllable Selenization Engineering

Bi-directional photodetection with positive and negative photoconductance (PPC/NPC) plays a critical role in building next-generation artificial neuromorphic systems, visual information processing and optoelectronic logic gates of the future. However, the typical device configuration based on heterostructures with strict working principles restricts the diversity of material selection. In this work, a novel strategy is proposed to fabricate bi-directional photoresponse devices based on PtSe2-x films with precisely controllable selenization engineering. It is found that the PtSe2-x films are composed of Pt and PtSe2 components. The direction of the photocurrent can be reversibly modulated in a broadband range by tuning the ratio of PtSe2 in the film, which is ascribed to the synergistic mechanism of bolometric effect of Pt and photoconductive effect of PtSe2. The polarity switching wavelength from NPC to PPC can be further modulated through tuning the components of the film for specific demand. The tunable bi-directional photoresponse enables the device to mimic the fundamental functions of artificial synapses all optically, such as aversion learning capability and logical functions, with high paired pulse facilitation index. This work potentially opens an opportunity for the development of advanced artificial neuromorphic systems and optoelectronic logic gates.