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 Ag 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.