Thickness Scaling Effects on the Complex Optical Conductivity of Few‐Layer WSe₂ Investigated by Spectroscopic Ellipsometry

Abstract

2D WSe2 have attracted widespread attentions as an ideal platform for new type optoelectronic and nanoelectronics applications. Understanding the intrinsic thickness scaling effects in complex optical conductivity of 2D, WSe2 is vital for WSe2‐based photonic and optoelectronic devices. Herein, complex optical conductivities of 1–5 layers in the energy range of 0.73–6.42 eV by spectroscopic ellipsometry with the classical slab model have been determined. Up to eight feature peaks (A–H) are observed in the optical conductivity spectra, and the central energies of these peaks are identified by the differential spectrum analysis method. These central energies exhibit interesting layer dependencies due to the thickness scaling effects. Specifically, for the low‐energy feature peaks A–E, their central energies decrease with the thickness increasing. But for the high‐energy feature peaks G and H, their central energies first show significant blueshifts and then redshifts as the thickness increases. These novel layer‐dependent evolvements are attributed in the optical conductivity of few‐layer WSe2 to the competition mechanism between the decreasing exciton binding energy and the band gap narrowing.

Analyzing the Influence of Imaging Resolution on Polarization Properties of Scattering Media Obtained From Mueller Matrix

“…Some recent researches have shown that the polarization imaging method can better preserve the microstructural information of the sample when imaging resolution decreased compared to unpolarized optical imaging methods ( Shen et al, 2020 ; Liu et al, 2021 ; Chen et al, 2022 ; Yao et al, 2022 ). It indicates that adopting the polarization imaging method can well balance the requirements of imaging resolution and FOV, to acquire the micro- and even nanostructural ( Dong et al, 2020 ; Chen et al, 2021a ; Wang et al, 2021 ; Fang et al, 2022 ) properties of the scattering medium quickly using a relatively low NA objective. In addition, to further obtain more quantitative information, many studies combined polarization parameters and image texture methods together to better distinguish characteristic tissue structures ( Liu et al, 2019 ; Zhai et al, 2022 ).…”

Comparative study of the influence of imaging resolution on polarization properties derived from Mueller matrix

“…Furthermore, the polarization imaging method can balance the requirements of imaging resolution and FOV 15,[25][26][27] . In order to quantitatively characterize the sample information, some studies applied the image texture analyzing method to the polarization parameters 21,[28][29][30][31] , so that the sample structures can be better distinguished.…”