P-type doping of MoS₂ thin films using Nb

We report on the first demonstration of p-type doping in large area few-layer films of (0001)-oriented chemical vapor deposited MoS₂. Niobium was found to act as an efficient acceptor up to relatively high density in MoS₂ films. For a hole density of 3.1 × 10²⁰ cm^-3, Hall mobility of 8.5 cm² V^-1 s ^-1 was determined, which matches well with the theoretically expected values. X-ray diffraction scans and Raman characterization indicated that the film had good out-of-plane crystalline quality. Absorption measurements showed that the doped sample had similar characteristics to high-quality undoped samples, with a clear absorption edge at 1.8 eV. Scanning transmission electron microscope imaging showed ordered crystalline nature of the Nb-doped MoS ₂ layers stacked in the [0001] direction. This demonstration of substitutional p-doping in large area epitaxial MoS₂ could help in realizing a wide variety of electrical and opto-electronic devices based on layered metal dichalcogenides.