Anisotropic Optical and Mechanical Properties in Few‐Layer GaPS₄

Abstract

Low‐symmetry 2D materials have received tremendous attention due to their anisotropic optical, electrical, and mechanical properties and viable candidates for polarized photodetectors, anisotropic field‐effect transistors, and nanomechanical systems. Here, an interesting low‐symmetry 2D material (GaPS4) is reported and its in‐plane anisotropic structure, optical, and mechanical properties are investigated. The polarized Raman and absorption spectra prove the sensitivity of GaPS4 to crystalline orientation and linear dichroism. The experimental results of azimuth‐dependent reflectance difference microscopy can visually reveal the in‐plane optical anisotropy of GaPS4 flakes. Moreover, an interesting pressurized bubble method is designed to verify the anisotropic mechanical properties of GaPS4 flakes and saddle‐like bubble devices of GaPS4 are successfully fabricated. The saddle‐like bubble devices exhibit visual anisotropic deflection variations along the orthogonal direction. Kelvin probe force microscope enables the direct identifying of the surface potential distribution of bubble devices under strain. Interest would be excited in the anisotropic optical and mechanical properties and relevant device applications of low‐symmetry 2D materials.

Low-dimensional van der Waals materials for linear-polarization-sensitive photodetection: materials, polarizing strategies and applications

“…As proof of the conception, in 2018, Chen et al unveiled that black arsenic exhibited remarkable anisotropy between the armchair direction and the zigzag direction in terms of its electrical conductance, carrier mobility, and thermal conductivity [107]. Most recently, Liu et al have discovered the anisotropic Raman scattering behaviors in the GaPS 4 nanosheets [113]. For clarity, figure 3 presents the crystal structures of some typical anisotropic 2D vdWMs.…”

“…In contrast to the widely explored group VIB transition metal dichalcogenides, the fundamental atomic layers of a considerable portion of 2D vdWMs host in-plane anisotropy [105]. The typical members of this family include the group VA elemental semiconductors [106,107], IVA-VIA compounds [108,109], group VIII transition metal dichalcogenides [110,111], multielemental vdWMs [112][113][114], etc. Accordingly, the low-symmetry lattice structures endow these materials with anisotropic physical properties, such as the anisotropic energy dispersion, laying a solid foundation for the realization polarized devices.…”

Divergent Vibrational Property Induced by an Anomalous Layer Sequence in Two-Dimensional GaPS4

“…In particular, the ν 1 peak is an RS mode that has been observed in other papers but not identified. 21 On the other hand, ν 2 , ν 3 , and ν 4 are peaks that are found in all of the different types, but the intensity of the peak changes significantly for each type (Figure 1c). Peaks ν 2 and ν 4 are significantly enhanced in type 2; specifically, the intensity of the ν 4 peak is greater than that of the ν 3 peak in type 2.…”

“…In addition, it is the main reason that the ν 1 peak was not previously identified in the previous study despite being observed, as they considered only the AA sequence of GaPS 4 when analyzing the origin of the RS peak. 21 On the other hand, ν 2 is the AA-sequence-oriented A g mode of the GaS-PS vibration, and the high intensity of the ν 2 peak in type 2 indicates that it contains relatively more AA sequences (Figure 2c). Among the four peaks, the most significant criterion for distinguishing between types 1 and 2 is the intensity ratio of ν 3 and ν 4 .…”

Extra‐High Mechanical and Phononic Anisotropy in Black Phosphorus Blisters

“…Bulge device has been a reliable yet facile way to generate a biaxial strain field to measure the elastic mechanical properties of ultrathin 2D materials, such as Young's modulus and bending rigidity, as well as interfacial parameters. [19] Meanwhile, the biaxial strain feature of 2D blisters offers an efficient way to tailor the band gap of transition metal dichalcogenide (TMD) materials, [16,20] control surface potential distribution, [21] monitor plasmon propagation, [22] and evaluate the Grüneisen parameters of graphene, [23] MoS 2 , and VS 2 . [24] However, for lowsymmetry anisotropic 2D materials, such as ReSe 2 , the bandgap response to mechanical strain is particularly sensitive to the loading direction.…”