P-type doping in edge-enriched MoS2−x nanostructures via RF-generated nitrogen plasma†

Abstract

In this work, we report an intuitive magnetron sputtering technique for the synthesis of vertically aligned MoS₂ (v-MS) nanostructures. The morphology and orientation of the as-synthesized nanostructures can be modified by altering the parameters of the sputtering process. This work emphasizes the versatility of magnetron sputtering to synthesize edge-enriched vertically aligned 2D nanostructures. These structures have diverse applications, such as those in optoelectronics, hydrogen evolution, sensing, energy storage and catalysis. The vertically aligned nanostructure of MoS₂ was confirmed using the field emission scanning electron microscopy and Raman spectroscopy techniques. Furthermore, we studied the plasma-based nitrogen doping process with minimal damage for introducing nitrogen atoms into 2D nanomaterials. A plasma discharged into a nitrogen environment, assisted by a simple radio frequency (RF) power supply, was employed for p-type doping in v-MS. The successful doping of nitrogen was investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy images confirmed the little surface damage resulting from the nitrogen doping technique. The change in work function resulting from doping was examined by Kelvin probe force microscopy and ultraviolet photoelectron spectroscopy. Optical emission spectroscopy (OES) study revealed the role of nitrogen plasma ions in doping with minimal surface damaging. This work demonstrates the effective alteration of the work function of the MoS₂ nanomaterial via plasma treatment.