Etching Techniques in 2D Materials

2D materials including graphene, transition metal dichalcogenides, and phosphorene have been widely researched for electronic and optoelectronic applications in recent years. Etching techniques for controlling the layer number and patterning shape of layered materials have been demonstrated to be a crucial part of the fabrication of various functional devices. Six types of etching techniques used in 2D materials are discussed, and the mechanism, purpose, and advantages of each technique are explored. In addition to the mature etching techniques widely used in thin-film semiconductors processing such as reactive ion etching and reactive gas etching, distinct etching techniques adpoted for 2D materials including self-limited atomic layer etching, metal-assisted splitting, laser etching, and thermal annealing are introduced in detail. In particular, the modification of 2D materials resulting from etching-induced defects, in particular changes to the electrical and optical properties, are discussed. Due to of the reduced dimensions and layered property of 2D materials, etching with atomic-layer precision, anisotropy, and selectivity can be required to control the layer number and edge or define some nanostructures and special structures. Recent advances are presented for further clarification. The diversity of etching techniques effectively facilitates the development of functional devices based on 2D materials.