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.

Optical-Based Thickness Measurement of MoO3 Nanosheets

“…The direct comparison between the AFM and the optical images allows us to build up a color-chart correlating the apparent color of the MoO 3 flakes deposited on top of the 297 nm SiO 2 /Si substrate (the SiO 2 thickness is experimentally measured by reflectometry with ±0.5 nm uncertainty) with their corresponding thickness with an uncertainty of ±3 nm. Similar approaches have been reported for graphene [ 45 ], transition metal dichalcogenides [ 46 ], TiS 3 [ 47 ] and franckeite [ 48 ]. This method has the main limitation that it requires the use of a specific SiO 2 thickness as the interference colors of the MoO 3 flakes strongly depend on the underlying substrate.…”

Birefringence and Dichroism in Quasi‐1D Transition Metal Trichalcogenides: Direct Experimental Investigation

“…This result indicates that both TiS 3 and ZrS 3 have inplane optical anisotropy properties, which is consistent with the previous and experimental results. [13][14][15][16] In this work, the electronic and optical properties were computed by using first-principles methods, which are programmed in Vienna ab initio simulation package. [28][29][30][31] The electron exchange-correlation is treated with generalized gradient approximation of Perdew-Burke-Ernzerhof.…”

“…[6] Among all kinds of optical anisotropic materials, transition metals trichalcogenides (TMTC) materials have attracted more attention due to their unique crystal structure, optical properties and electrical properties. [7][8][9][10][11][12][13][14][15] Among the numerous TMTC materials, there is a material system MS 3 (M = Ti, Zr, Hf) the transition metal element as the IVB group element, and the ratio of transition metal element to sulfur element is 1:3. MS 3 bulk materials are wire-like crystals, and the mono-layered materials obtained by mechanically separated are nanoribbons with quasi-1D structure.…”

Thickness Identification of Thin InSe by Optical Microscopy Methods

“…It is well known that graphene, transition metal dichalcogenides (TMDCs), TiS 3 , franckeite, mica, antimonene and MoO 3 flakes deposited on a SiO 2 /Si substrate present different colors depending on their thickness and on the SiO 2 thickness. [16,[49][50][51][52][53][54] A comprehensive analysis of the apparent colors can yield a quick guide to estimate the thickness of 2D materials in a similar fashion as the thickness of SiO 2 capping layers on Si wafers is estimated from its interference color. Figure 2a shows the AFM topography of seven InSe flakes with thicknesses ranging from %4 to %90 nm, and Figure 2b shows their corresponding optical microscopy images on 270 nm SiO 2 /Si substrate (the SiO 2 thickness has been experimentally determined by reflectometry with AE0.5 nm uncertainty).…”