Orientation-dependent optical characterization of atomically thin transition metal ditellurides

Molybdenum ditellurides (MoTe₂) have recently attracted attention owing to their excellent structurally tunable nature between 1T′(metallic)- and 2H(semiconducting)-phases; thus, the controllable fabrication and critical identification of MoTe₂ are highly desired. Here, we semi-controllably synthesized 1T′- and 2H-MoTe₂ crystals using the atmospheric pressure chemical vapor deposition (APCVD) technique and studied their grain-orientation dependency using polarization-sensitive optical microscopy, Raman scattering, and second-harmonic generation (SHG) microspectroscopy. The polycrystalline 1T′-MoTe₂ phase with quasi-1D "Mo-Mo" zigzag chains showed anisotropic optical absorption, leading to a clear visualization of the lattice domains. On the other hand, 2H-MoTe₂ lattice grains did not exhibit any discernible difference under polarized light illumination. The combined aforementioned microscopy techniques could be used as an easy-to-access and non-destructive tool for a quick and solid identification of intended lattice orientation development in industry-scale MoTe₂ crystal manufacturing.