Anisotropic\nEtching of Atomically Thin MoS₂

Abstract

Exposure to oxygen at 300–340\n°C results in triangular etch pits with uniform orientation on\nthe surfaces of atomically thin molybdenum disulfide (MoS₂), indicating anisotropic etching terminating on lattice planes.\nThe triangular pits grow laterally with oxidation time. The density\nof pits scarcely depends on oxidation time, temperature, and MoS₂ thickness but varies significantly from sample to sample,\nindicating that etching is initiated at native defect sites on the\nbasal plane surface rather than activated by substrate effects such\nas charged impurities or surface roughness. Raman spectroscopy confirms\nthat oxygen treatment produces no molybdenum oxide (MoO₃) below 340 °C. However, upon oxidation above 200 °C, the\nRaman A_1g mode upshifts and the linewidth decreases, indicating\np-type doping of MoS₂. Oxidation at 400 °C results\nin complete conversion to MoO₃.