Defect engineering of two-dimensional transition metal dichalcogenides

Abstract

Two-dimensional transition metal dichalcogenides (TMDs), an emerging family of layered materials, have provided researchers a fertile ground for harvesting fundamental science and emergent applications. TMDs can contain a number of different structural defects in their crystal lattices which significantly alter their physico-chemical properties. Having structural defects can be either detrimental or beneficial, depending on the targeted application. Therefore, a comprehensive understanding of structural defects is required. Here we review different defects in semiconducting TMDs by summarizing: (i) the dimensionalities and atomic structures of defects; (ii) the pathways to generating structural defects during and after synthesis and, (iii) the effects of having defects on the physico-chemical properties and applications of TMDs. Thus far, significant progress has been made, although we are probably still witnessing the tip of the iceberg. A better understanding and control of defects is important in order to move forward the field of Defect Engineering in TMDs. Finally, we also provide our perspective on the challenges and opportunities in this emerging field.

Defect Structure of Localized Excitons in a WSe2 Monolayer

“…We further discovered on the same sample that these vacancy defects dominated the low temperature optical spectra as localized excitons. For the first time, our work shed light on the atomic-scale defect structure of localized excitons in the WSe 2 monolayer and paved the way toward defect engineering for SQEs in TMD monolayers and other 2D materials in general [7][8][9].…”

“…In addition, the photoluminescence quantum yield is unexpectedly low for a direct-gap semiconductor [6]. All these facts suggest that structural defects in TMD monolayers play significant roles in the electronic and optical properties [7][8][9].…”

Interlayer Nanoarchitectonics of Two‐Dimensional Transition‐Metal Dichalcogenides Nanosheets for Energy Storage and Conversion Applications

“…This high temperature preparation of the intercalated materials excluded formation of the thermally unstable 1T-phase in the product. [49] DFT calculations reveal that to accommodate the intercalated K atoms, the c lattice parameter of 2H-MoS 2 can be dramatically increased to 15.871 Å for K 0.25 MoS 2 . [50] In order to ameliorate the experimental conditions necessary for the metal vapor intercalation (high temperature or long reaction time), an electrochemical intercalation method was developed.…”

“…[1][2][3][4][5] Owing to their high anisotropy and unique crystal structures, MX 2 can be utilized in a variety of energy conversion and storage applications, including water splitting cells, rechargeable batteries, supercapacitors, fuel cells, as well as various electronic and optoelectronic devices, etc. [6][7][8][9][10][11] Nanoengineering (morphology, size, number of layers, edges, defects), [12][13][14][15][16][17] phase conversion, [18][19][20][21][22][23] and composition tuning (alloying, doping with foreign transition metal), [24][25][26][27][28][29][30][31] represent the hot research areas in the recent past, aiming at modulation of the material properties and improvement of the device performances. Such impressive progress benefits from the success in synthesizing nanostructured MX 2 with precisely controlled parameters including edge density and crystalline phase.…”

Micro-Extinction Spectroscopy (MExS): a versatile optical characterization technique

“…At monolayer thickness, TMDs can exhibit direct electronic and optical bandgaps ranging from the visible to the near-infrared. Optical spectroscopy techniques such as photoluminescence (PL) and Raman are currently the key methods used in studying TMD properties such as bandgap energy, [15,16] emission efficiency, [17][18][19] and defect density [19][20][21]. However, PL and Raman spectroscopies have limited quantum efficiency, making them unfit for high-throughput applications.…”