Mixed-Connectivity GeS4 Framework for Wavelength-Dependent Linear Dichroism in Layered GeS2

Abstract

Abstract Polyhedral connectivity offers a crystal-chemical route for understanding anisotropic properties in low-symmetry solids. Here, layered monoclinic GeS2 is investigated as a mixed-connectivity tetrahedral system composed of corner-sharing Ge−S−Ge bridges and edge-sharing Ge2S2 units. Polarization-resolved Raman spectroscopy combined with phonon calculations reveals strongly mode-dependent vibrational polarizability within the interconnected GeS4 framework. First-principles calculations show S-p-dominated valence states, Ge−S-hybridized conduction states, and an energy-dependent interchange of the preferred in-plane absorption direction. Polarization-resolved absorption measurements confirm this behavior through a sign change in the normalized linear-dichroism contrast between 266 and 336 nm. ADRDM further verifies spatially coherent dielectric anisotropy, while a GeS2 device converts the 266 nm optical anisotropy into a reproducible polarization-dependent photocurrent with a ratio of approximately 1.92. These results establish mixed GeS4 connectivity as a crystal-chemical framework linking lattice dynamics, electronic structure, and wavelength-dependent linear dichroism.