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.