Inspection of Line Defects in Transition Metal Dichalcogenides Using a Microscopic Hyperspectral Imaging Technique

Abstract

The line defects of two-dimensional (2D) transition metal dichalcogenides (TMDs) play a vital role in determining their device performance. In this work, a microscopic hyperspectral imaging technique based on differential reflectance was introduced for the online inspection of line defects in TMDs. Upon comparison of the measurement results of imaging and spectra, the relationship between optical contrast and differential reflectance spectra was established. A light selection method was proposed to optimize the optical contrast of line defects. Via application of an image processing algorithm, an automatic detection of the line defects with a classification accuracy of 95% was achieved for WS 2 , MoS 2 , and MoSe 2 . This work not only provides a microscopic hyperspectral imaging technique for detecting 2D material defects but also introduces a versatile design strategy for developing an advanced machine vision spectroscopic system.

Resonant Coherent Raman Scattering from WSe2

“…Briefly, both low signal levels and the typical spatial resolution of confocal Raman scattering are limiting, which motivated the use of nonlinear and plasmon-enhanced Raman micro-spectroscopy to characterize phonons in low-dimensional material systems . Excitons on the other hand are conventionally tracked through absorption/reflectance (extinction) and PL, both of which still suffer from (diffraction)-limited spatial resolution, , and from background scattering in the case of optical extinction-based measurements. Overcoming the diffraction limit is possible in plasmon-enhanced PL (i.e., TEPL), wherein the de-phased electronic process can be tracked on the nanoscale, as summarized in a recent review article .…”

“…Excitons in two-dimensional (2D) quantum materials can be optically excited and harnessed in modern optoelectronic devices. , This is true for intralayer excitons within individual atomically thin layers and also in low-dimensional heterostructures, e.g., of different transition-metal dichalcogenides (TMD), which have been shown to support long­(er)-lived interlayer excitons. , In the past few years, several methods based on photons, electrons, and photoelectrons have been developed and/or adapted to characterize excitons in space, time, and even real space–time (joint nano–femto scale). − In the realm of frequency-domain optical characterization of excitons in 2D materials, recent hyperspectral extinction as well as photoluminescence (PL) excitation measurements that are equally relevant to our present work come to mind.…”

“…1,2 In the past few years, several methods based on photons, electrons, and photoelectrons have been developed and/or adapted to characterize excitons in space, time, and even real space−time (joint nano−femto scale). 1−5 In the realm of frequency-domain optical characterization of excitons in 2D materials, recent hyperspectral extinction 6 as well as photoluminescence (PL) excitation measurements 7 that are equally relevant to our present work come to mind.…”

Defect identification of electricity transmission line insulators based on the improved lightweight network model with computer vision assistance

“…Presently, the integration of computer vision (CV) technology for assessing the condition of electricity transmission line structures and their associated components has transitioned into practical application. However, several challenges persist: 1) The model training dataset is unbalanced [ 5 ]. Applying deep learning (DL) models to defect detection requires massive labeled image data to train a high-precision and robust detection model.…”

Direct Assessment of Defective Regions in Monolayer MoS2 Field-Effect Transistors through In Situ Scanning Probe Microscopy Measurements

“…However, the discerning large variability in device characteristics rather requires the investigation of aberrant devices, which remains challenging by these techniques due to the strict requirements of specimen preparation, the limited field of view (FOV), and their sensitivity to even inactive defects. Thence, measurements of optical transitions associated with such defects seem more promising to make this correlation, − but so far, the 2D-FETs benchmarking by optical methods still remains to be shown which can be attributed to a complex relationship between excitonic, trionic and defect-associated recombinations, laser-induced damages, and so on.…”