Probing the Optical Properties of MoS2 on SiO2/Si and Sapphire Substrates

Abstract

As an important supplementary material to graphene in the optoelectronics field, molybdenum disulfide (MoS2) has attracted attention from researchers due to its good light absorption capacity and adjustable bandgap. In this paper, MoS2 layers are respectively grown on SiO2/Si and sapphire substrates by atmospheric pressure chemical vapor deposition (APCVD). Atomic force microscopy, optical microscopy, and Raman and photoluminescence spectroscopy are used to probe the optical properties of MoS2 on SiO2/Si and sapphire substrates systematically. The peak shift between the characteristic A1g and E12g peaks increases, and the I peak of the PL spectrum on the SiO2/Si substrate redshifts slightly when the layer numbers were increased, which can help in obtaining the layer number and peak position of MoS2. Moreover, the difference from monolayer MoS2 on the SiO2/Si substrate is that the B peak of the PL spectrum has a blueshift of 56 meV and the characteristic E12g peak of the Raman spectrum has no blueshift. The 1- and 2-layer MoS2 on a sapphire substrate had a higher PL peak intensity than that of the SiO2/Si substrate. When the laser wavelength is transformed from 532 to 633 nm, the position of I exciton peak has a blueshift of 16 meV, and the PL intensity of monolayer MoS2 on the SiO2/Si substrate increases. The optical properties of MoS2 can be obtained, which is helpful for the fabrication of optoelectronic devices.

An In Situ Reflectance Spectroscopic Investigation to Monitor Two-Dimensional MoS2 Flakes on a Sapphire Substrate

“…It is worth to mention that the frequency difference between the E 1 2g and A 1g is sensitive to the layer thickness. Raman frequency difference of MoS 2 flakes is ~19.6 cm −1 , in good agreement with that of monolayer MoS 2 in previous studies [ 32 ]. Thus, the thickness for the sample can be interpreted by a monolayer structure.…”

“…Additionally, AFM was used to assess the thickness of as-grown MoS 2 flakes on the sapphire. A height profile along the black broken line is about 0.85 nm in Figure 4 d, which is consistent with the results of monolayer MoS 2 thickness reported in the literature [ 32 , 33 ]. An AFM image in the inset of Figure 4 d reveals that the sample has the classic monolayer topography.…”

Twisted Light-Enhanced Photovoltaic Effect

“…These peaks were identified as contributions by the A excitons (∼1.837 eV), B excitons (∼1.98 eV), and negative trions (∼1.80 eV). 30,31 Raman measurements of the device channel (Figure 1(d)), on the other hand, showed the two dominant phonon modes of MoS 2 . 30,32 Fixed optical power (P laser ) was used in each set of measurements to ensure that the corresponding analysis were based on the fact that almost consistent amount of photons per unit time goes to the sample.…”

Intelligent Identification of MoS2 Nanostructures with Hyperspectral Imaging by 3D-CNN

“…Figure 1 shows the processing step before the data enters the model. Layer number labeling of the manual area circle mask (Mask) is performed and the data are divided when the captured image is converted into a spectrum image by using a hyperspectral image technology; we will measure the result on the basis of the Raman spectrum ( Figure S3 ) [ 50 , 51 , 52 , 53 , 54 ]. The categories are substrate, monolayer, bilayer, trilayer, bulk, and residues, which are our ground truths.…”