Air-stable n-doped black phosphorus transistor by thermal deposition of metal adatoms.

In this work, a simple and effective thermal deposition method is described to enhance the stability and achieve n-doping of two-dimensional black phosphorus (BP), resulting in the successful fabrication of logic devices. By doping with Al adatoms, the stability of BP against oxidation is enhanced and the transfer characteristics are maintained for several days under ambient conditions. Furthermore, the resulting BP is n-doping showing a negative-shifted threshold voltage and enhanced electron mobility. The mechanism of Al-doping is investigated by first-principles calculation and Al induces a downward shift of the conduction band minimum and increases the Fermi level. In addition, integration of bare BP and Al-doped BP enables the fabrication of various logic devices such as inverters and p-n diodes. This work reveals a facile strategy to simultaneously enhance the stability and regulate the conductivity of BP by doping with metal adatoms boding well for device applications.