Strain engineering of quasi-1D layered TiS₃ nanosheets toward giant anisotropic Raman and piezoresistance responses

Quasi-one-dimensional layered TiS₃ nanosheets possess highly anisotropic physical properties. Herein, we reported the anisotropic strain response of Raman and the piezoresistance effect in layered TiS₃ nanosheets. An attractive Grüneisen parameter (⁠$γm$⁠) of 5.82 was achieved for $AgIII$ mode in the b-axis strained TiS₃ nanosheet, while a negligible value of $γm$ was obtained when the strain is applied along the a-axis direction. We also revealed the opposite piezoresistive effect with strains applied along the two principal axes, demonstrating a gauge factor ratio of approximately −1:3.2. The giant anisotropy is attributed to the strain modulated bandgap, which was further confirmed by density functional theory calculations.