Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, Delft 2628 CJ, The Netherlands.
Nanoscale. 2018 Jul 9;10(26):12424-12429. doi: 10.1039/c8nr03616k.
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.
TiS3 纳米片因其直接的窄带隙和强的光物质相互作用，已被证明是超薄光电器件有前途的候选材料。此外，TiS3 的显著面内各向异性吸引了人们对偏振敏感光电器件的研究。在本文中，我们研究了 SiO2/Si 衬底上不同厚度的 TiS3 纳米片的光学对比度，从中我们获得了可见光谱中的复折射率。我们发现 TiS3 表现出非常大的双折射，比已知的强双折射材料如 TiO2 或方解石更大，并且具有线性二色性。这些发现与从头算计算定性一致，表明材料的双折射和线性二色性源于激子起源。
