Orientation controllable growth of MoO₃ nanoflakes: Micro-raman, field emission, and birefringence properties

A simple but effective way to control the orientational arrangement of MoO3 nanoflakes is presented, which offers an opportunity to investigate the anisotropic properties of different crystallographic faces. Their electrical and optical properties are investigated. According to the polarized micro-Raman spectra, oxygen vacancies preferred to be located at the sharp side edges of the lamella, which might play an important role in the catalytic properties of samples. Ascribing to the unique structural geometry and the oxygen-defects-induced reduction of the work function, the electron field emission properties of the samples show that the erect MoO3 nanoflakes are potential candidates for the cold-cathode-based electronics. Furthermore, strong optical birefringence properties of samples are also first observed.