Strong In-Plane Anisotropies of Optical and Electrical Response in Layered Dimetal Chalcogenide

An interesting in-plane anisotropic layered dimetal chalcogenide Ta₂NiS₅ is introduced, and the optical and electrical properties with respect to its in-plane anisotropy are systematically studied. The Raman vibration modes have been identified by Raman spectra measurements combined with calculations of phonon-related properties. Importantly, the Ta₂NiS₅ flakes exhibit strong anisotropic Raman response under the angle-resolved polarized Raman spectroscopy measurements. We found that Raman intensities of the A_g mode not only depend on rotation angle but are also related to the sample thickness. In contrast, the infrared absorption with light polarized along the a axis direction is always larger than that in the c axis direction regardless of thickness under the polarization-resolved infrared spectroscopy measurements. Remarkably, the first-principles calculations combined with angle-resolved conductance measurements indicate strong anisotropic conductivity of Ta₂NiS₅. Our results not only prove Ta₂NiS₅ is a promising in-plane anisotropic 2D material but also provide an interesting platform for future functionalized electronic devices.