Large birefringence and linear dichroism in TiS₃ nanosheets

Abstract

TiS₃ nanosheets have proven to be promising candidates for ultrathin optoelectronic devices due to their direct narrow band-gap and the strong light-matter interaction. In addition, the marked in-plane anisotropy of TiS₃ is appealing for the fabrication of polarization sensitive optoelectronic devices. Herein, we study the optical contrast of TiS₃ nanosheets of variable thickness on SiO₂/Si substrates, from which we obtain the complex refractive index in the visible spectrum. We find that TiS₃ exhibits very large birefringence, larger than that of well-known strong birefringent materials like TiO₂ or calcite, and linear dichroism. These findings are in qualitative agreement with ab initio calculations that suggest an excitonic origin for the birefringence and linear dichroism of the material.