Strong in-plane optical anisotropy in 2D van der Waals antiferromagnet VOCl

Two-dimensional(2D)van der Waals(vdW)magnetic materials with strong in-plane anisotropy can make possible novel applications such as optospintronics and strain sensors.In this work,the strong in-plane optical anisotropy in 2D vdW antiferromagnet VOCl has been systematically investigated.The optical brightness and absorption coefficient exhibit evident periodic variation with the change of incident polarization,unveiling the strong in-plane anisotropic optical absorption.The Raman intensity in this material shows obvious dependence on the polarization angle of incident laser,demonstrating that the phonon properties possess strong in-plane anisotropy.Besides,we have also realized in-situ visualization of in-plane optical reflection anisotropy in this material.Moreover,the strong second harmonic generation(SHG)signal can only be detected when the incident polarization is along specific in-plane crystal orientations,illustrating the presence of strong in-plane nonlinear optical anisotropy.These findings will benefit the applications of VOCl in the field of polarization-dependent electronics and spintronics.

Polarization-sensitive and wide-spectrum photovoltaic detector based on quasi-1D ZrGeTe_(4)nanoribbon

Low-dimensional semiconductors with in-plane anisotropy and narrow bandgap have been extensively applied to polarized detection in the near-infrared(NIR)region.However,the narrow bandgap can cause noise owing to the high dark current in photodetectors.This article reports quasi-1D ZrGeTe_(4)nanoribbonbased photodetectors with low dark current and broadband polarization detection.The photodetector was fabricated by evaporating 50-nm-thick Au electrodes on a ZrGeTe_(4)nanoribbon.Benefiting from the photovoltaic characteristics in the ZrGeTe_(4)nanoribbon and Au electrodes,these photodetectors can operate without bias voltage,with decreased dark current,and improved device performance.Furthermore,the quasi-1D ZrGeTe_(4)nanoribbon-based photodetectors demonstrate a polarization sensitivity in a broadband from visible(VIS)to the NIR region,such as a high photoresponsivity of 625.65 mA W1,large external quantum efficiency of 145.9%at 532 nm,and photocurrent anisotropy ratio of 2.04 at 1064 nm.They exhibit a novel perpendicular optical reversal of 90in polarization-sensitive photodetection,angle-resolved absorption spectra,and azimuth-dependent reflectance difference microscopy(ADRDM)from VIS to the NIR region,as opposed to other nanoribbon-based polarization-sensitive photodetectors.This work paves the way for utilizing photovoltaic photodetectors based on low-dimensional materials for broad-spectrum polarized photodetection.

Polarization Measurement Method Based on Liquid Crystal Variable Retarder(LCVR)for Atomic Thin-Film Thickness

Atomic thickness thin films are critical functional materials and structures in atomic and close-to-atomic scale manufacturing.However,fast,facile,and highly sensitive precision measurement of atomic film thickness remains challenging.The reflected light has a dramatic phase change and extreme reflectivity considering the Brewster angle,indicating the high sensitivity of the optical signal to film thickness near this angle.Hence,the precision polarization measurement method focusing on Brewster angle is vital for the ultrahigh precision characterization of thin films.A precision polarization measurement method based on a liquid crystal variable retarder(LCVR)is proposed in this paper,and a measurement system with a high angular resolution is established.A comprehensive measurement system calibration scheme is also introduced to accommodate ultrahigh precision film thickness measurement.Repeatable measurement accuracy to the subnanometer level is achieved.Standard silicon oxide film samples of different thicknesses were measured around Brewster angle using the self-developed system and compared with a commercial ellipsometer to verify the measurement accuracy.The consistency of the thickness measurement results demonstrates the feasibility and robustness of the measurement method and calibration scheme.This study also demonstrates the remarkable potential of the LCVR-based polarization method for atomic film thickness measurement in ultraprecision manufacturing.