Isotropic conduction and negative photoconduction in ultrathin PtSe2 films

PtSe2 ultrathin films are used as the channel of back-gated field-effect transistors that are investigated at different temperatures and under super-continuous white laser irradiation. The temperature-dependent behavior confirms the semiconducting nature of multilayer PtSe2, with p-type conduction, a hole field-effect mobility up to 40 cm2 V−1 s−1, and significant gate modulation. Electrical conduction measured along different directions shows isotropic transport. A reduction of PtSe2 channel conductance is observed under exposure to light. Such a negative photoconductivity is explained by a photogating effect caused by photo-charge accumulation in SiO2 and at the Si/SiO2 interface.