Highly anisotropic mechanical and optical properties of 2D layered As2S3 membranes
M. Siskins (TU Delft - QN/Steeneken Lab, Kavli institute of nanoscience Delft)
Martin Lee (TU Delft - QN/Steeneken Lab, Kavli institute of nanoscience Delft)
Farbod Alijani (TU Delft - Dynamics of Micro and Nano Systems)
M van Blankenstein (Student TU Delft, Kavli institute of nanoscience Delft)
D. Davidovikj (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
H. S.J. van der Zant (TU Delft - QN/van der Zant Lab, Kavli institute of nanoscience Delft)
Peter Steeneken (Kavli institute of nanoscience Delft, TU Delft - QN/Steeneken Lab, TU Delft - Dynamics of Micro and Nano Systems)
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Abstract
Two-dimensional (2D) materials with strong in-plane anisotropy are of interest for enabling orientation-dependent, frequency-tunable, optomechanical devices. However, black phosphorus (bP), the 2D material with the largest anisotropy to date, is unstable as it degrades in air. In this work we show that As2S3 is an interesting alternative, with a similar anisotropy to bP, while at the same time having a much higher chemical stability. We probe the mechanical and optical anisotropy in As2S3 by three distinct angular-resolved experimental methods: Raman spectroscopy, atomic force microscopy (AFM), and resonance frequency analysis. Using a dedicated angle-resolved AFM force-deflection method, an in-plane anisotropy factor of EaEc=1.7 is found in the Young's modulus of As2S3 with Ea-axis = 79.1 ± 10.1 GPa and Ec-axis = 47.2 ± 7.9 GPa. The high mechanical anisotropy is also shown to cause up to 65% difference in the resonance frequency, depending on crystal orientation and aspect ratio of membranes.
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