Thickness-dependent patterning of MoS₂ sheets with well-oriented triangular pits by heating in air

Patterning ultrathin MoS₂ layers with regular edges or controllable shapes is appealing since the properties of MoS₂ sheets are sensitive to the edge structures. In this work, we have introduced a simple, effective and well-controlled technique to etch layered MoS₂ sheets with well-oriented equilateral triangular pits by simply heating the samples in air. The anisotropic oxidative etching is greatly affected by the surrounding temperature and the number of MoS₂ layers, whereby the pit sizes increase with the increase of surrounding temperature and the number of MoS₂ layers. First-principles computations have been performed to explain the formation mechanism of the triangular pits. This technique offers an alternative avenue to engineering the structure of MoS₂ sheets.