Etching Techniques in 2D Materials

Abstract

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.

Bioelectronics‐Related 2D Materials Beyond Graphene: Fundamentals, Properties, and Applications

“…[ 149 ] Based on the absence of covalent bonding between 2D materials and substrates, metal‐assisted splitting has been developed to eliminate etching‐induced contamination. [ 169,170 ] Specifically, 2D materials covered by a photoresist are defined by lithography and then deposited on a metal film, and a certain region of the 2D material defined by lithography is then peeled off to achieve patterning. As a lithography‐free technique, direct laser writing can locally heat and thin 2D materials without the use of masks, and precise control of laser movement and power allows one to realize diverse patterns with different numbers of layers.…”

Recent progress and challenges on two-dimensional material photodetectors from the perspective of advanced characterization technologies

“…So it's essential to control the layer number accurately. Several methods have been explored, such as layer etching, reactive gas etching, and metal-assisted splitting [86]. Das et al reported the controlled thickness of PdSe2 by SF6+N2 plasma, as shown in Fig.…”

“…With the thickness decreasing from 9 layers to monolayer, the bandgap of WSe2 increases from 1.42 to 1.65 eV [149]. Because the thickness can be factitiously controlled, the layer-dependent bandgap makes it possible to design devices for a certain wavelength [86]. The layerdependent band structures affect not only photoresponse but also electronic transportation.…”

Synthesis of Wet‐Chemically Prepared Porous‐Graphene Single Layers on Si/SiO2 Substrate Increasing the Photoluminescence of MoS2 in Heterostructures

“…[24] Nanometer-sized pores were created in graphene by oxygen plasma or other plasmas. [25,26] Moreover, pores on the nanoscale were created in few-layered graphene using oxygen, ozone, or liquid phase etching using HNO 3 solution as etching reagents. [26][27][28] In addition, it is reported that a single Ni atom can be used to cut graphene to a nanomesh with a pore size of about 10-50 nm.…”

“…[25,26] Moreover, pores on the nanoscale were created in few-layered graphene using oxygen, ozone, or liquid phase etching using HNO 3 solution as etching reagents. [26][27][28] In addition, it is reported that a single Ni atom can be used to cut graphene to a nanomesh with a pore size of about 10-50 nm. [29] Sub-nanometer diameter pores in singlelayer graphene membranes were also fabricated, accordingly, defects were introduced into the graphene lattice through ion bombardment and oxidative etching enlarged defects into pores with sizes of 0.40 ± 0.24 nm.…”