Extrinsic p-type doping of few layered WS2 films with niobium by pulsed laser deposition

Doping of few layered 2H WS2 films with Nb by pulsed laser deposition (PLD) using ablation targets fabricated from WS2, S and Nb powders is reported. The undoped controls were n-type, exhibited a Hall mobility of 0.4 cm(2) /Vs, and characterized by a Fermi level at 1.41 eV from the valence band edge. The latter was determined using ultraviolet photoelectron spectroscopy. Films doped at 0.5 and 1.1 atomic percentages niobium were p-type, and characterized by Fermi levels at 0.31 eV and 0.18 eV from the valence band edge. X-ray photoelectron spectroscopy indicates that Nb substitutes on W lattice sites. With increased Nb doping, the hole sheet concentration increased from 3.9 x 10(12) to 8.6 x 10(13) cm(-2), while the mobility decreased from 7.2 to 2.6 cm(2) /Vs, presumably due to increased ionized impurity scattering. The approach demonstrates the potential of PLD for controlled doping of transition metal dichalcogenides. Published by AIP Publishing.