Centimeter-sized 2D alpha-MoO3 single crystal: growth, Raman anisotropy, and optoelectronic properties

Centimeter-sized 2D layered alpha-MoO3 single crystal has been grown by a facile physical vapor deposition method. The lateral size of alpha-MoO3 single crystals can be tunable from micrometer to centimeter by controlling the inner diameter of the quartz tube reaction chamber. The as-grown alpha-MoO3 exhibits strong in-plane Raman anisotropy, where A(g) Raman modes give the direction of crystallographic orientation, which can be used to rapidly and precisely identify the crystallinity of large-area alpha-MoO3 through selected-area angel-resolved polarized Raman spectroscopy. Moreover, the photodetectors based on annealed alpha-MoO3 single crystals exhibit excellent optoelectronic performance with a photoresponsivity of 65.6 A W-1 and a fast photoresponse time of 2 s.