Horizontally Oriented Growth of Highly Conductive MoO₂ Nanobelts on Sapphire

Controlling the growth direction of one-dimensional (1D) nanostructures is crucial for their resulting applications. In this work, the growth of MoO2 nanobelts was directed into three directions on a flat C-plane sapphire and one direction on an annealed M-plane sapphire, respectively. Structural characterizations show that these MoO2 nanobelts have high crystal quality and grow epitaxially along a consistent [010] crystallographic orientation. UV–visible absorption spectra indicate that these self-oriented MoO2 nanobelts have a large intrinsic band gap of 3.9 eV. Angle-resolved polarized Raman spectra confirm that these nanobelts exhibit remarkable anisotropic properties. In situ conductivity measurements show that these MoO2 nanobelts have a high conductivity of 1.6 × 103 S/cm. Last, two self-assembly models are proposed for the horizontally oriented growth of these MoO2 nanobelts. These horizontally oriented MoO2 nanobelts are promising for potential applications in various new micro/nanophotonic and electronic devices.