$β-Ga_2O_3$ is a wide band gap semiconductor (Eg ≒4.8eV) with luminescence properties. Its conductivity depends on the environment. $β-Ga_2O_3$ exhibits ultraviolet, blue, and green luminescence properties and Overhauser effect. And $β-Ga_2O_3$ is a transparent conducting oxide (TCO).
One-dimensional gallium oxide structures were successfully grown by a vapor transport system without catalyst. The microstructure of gallium oxide structures were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The cathodoluminescence of gallium oxide structures was studied by FE-SEM with Mono-cathodoluminescence. It was identified from XRD data that the structures were $β-Ga_2O_3$ of which structure is monoclinic with space group of C2/m. $β-Ga_2O_3$ structures had film, particle, and one-dimensional shapes depending on the growth conditions. The thickness of one-dimensional $β-Ga_2O_3$ structures were from several tens nanometer to several hundreds nanometer. The thickness of one-dimensional $β-Ga_2O_3$ structures decreased with a decrease in growth temperature. Also, the thickness of those decreased with a decrease in growth time. It prove the two-step growth of the whisker. The tips of the one-dimensional structures have no anything. Therefore, one-dimensional $β-Ga_2O_3$ structures might were grown via the Vapor-Solid (VS) process. Various imperfection regions were observed in the one-dimensional $β-Ga_2O_3$ structures. And amorphous regions have been observed at the edge of some one-dimensional structures. Because of the peculiar crystal structure, one-dimensional $β-Ga_2O_3$ structures have been grown with altering the growth direction during the growth. The dendritic shape was observed in the growth of one-dimensional $β-Ga_2O_3$ structures. In the initial step of branching shape, the growth direction was continued as that of stem.
In the cathodoluminescence study, $β-Ga_2O_3$ structures showed various optical properties. The $β-Ga_2O_3$ film synthesized in this experiment appeared mainly ultraviolet (UV) luminescence. One-dimensional $β-Ga_2O_3$ structures exhibited from a UV to a visible ray luminescence. The thiner the thickness of one-dimensional structures become, the stronger the intensity of the visible ray luminescence does. But, the quantum effect did not clear at the one-dimensional $β-Ga_2O_3$ nanotructures. Such a luminescence property might be related with the complex structure of $β-Ga_2O_3$ . The same defects generated at the different site of the complex $β-Ga_2O_3$ crystal structure will differently affect in the optical property.
