Highly polarization sensitive photodetectors based on quasi-1D titanium trisulfide (TiS).

Photodetectors with high polarization sensitivity are in great demand in advanced optical communication. Here, we demonstrate that photodetectors based on titanium trisulfide (TiS) are extremely sensitive to polarized light (from visible to the infrared), due to its reduced in-plane structural symmetry. By density functional theory calculation, TiS has a direct bandgap of 1.13 eV. The highest photoresponsivity reaches 2500 A W. What is more, in-plane optical selection caused by strong anisotropy leads to the photoresponsivity ratio for different directions of polarization that can reach 4:1. The angle-dependent photocurrents of TiS clearly display strong linear dichroism. Moreover, the Raman peak at 370 cm is also very sensitive to the polarization direction. The theoretical optical absorption of TiS is calculated by using the HSE06 hybrid functional method, in qualitative agreement with the observed experimental photoresponsivity.