Tunable n-type and p-type doping of two-dimensional layered PdSe2via organic molecular adsorption

Palladium diselenide (PdSe2) is a two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductor with desirable properties for nanoelectronics. Here, we demonstrate that 2D layered PdSe2 adsorbed with two kinds of organic molecules, an electrophilic molecule tetracyano-p-quinodimethane (TCNQ) as an electron acceptor and a nucleophilic molecule tetrathiafulvalene (TTF) as an electron donor, can realize tunable p-type and n-type doping of 2D PdSe2 by using first-principles density functional theory (DFT) calculations. We find that TCNQ attracts electrons from PdSe2 and introduces shallow acceptor states close to the valence band edge, resulting in p-type doping of PdSe2, while TTF donates electrons into PdSe2 and introduces shallow donor states close to the conduction band edge, resulting in n-type doping of PdSe2. Furthermore, such p-type and n-type doping of PdSe2 can be efficiently controlled with an external electric field, interlayer distance and substrate thickness. Such effective bipolar doping of PdSe2via molecular adsorption would broaden its applications in nanoelectronics.