Influence of material synthesis and doping on the transport properties of WSe2 single crystals grown by selenium transport

Abstract Resistivity and Hall effect measurements of WSe 2 single crystals grown with excess selenium as transport agent in chemical vapor transport are presented. The electronic properties are shown to depend strongly on the materials selected for synthesizing polycrystalline powder used in the crystal growth procedure. Compensated high-resistivity samples of p-type doping were obtained with room-temperature carrier concentrations of p ≈ 10 12 cm −3 and activation energies of E A = 450 meV. Changing the starting material resulted in low-resistivity p-type samples with p ≈ 10 17 cm −3 and E A = 80 meV. Vanadium doping leads to degenerate p-type samples with p ≈ 10 19 cm −3 . Copper doping changes high resistivity material to n-type conductivity. No significant changes of transport properties are observed for doping with Au, Ni, Mo, Cr, and Fe. Evidence is presented that the effective mass of holes in WSe 2 is m h = 0.3 m 0 .