Crystallization, Phase Stability, Microstructure, and Chemical Bonding in Ga 2 O 3 Nanofibers Made by Electrospinning.

We report on the crystal structure, phase stability, surface morphology, microstructure, chemical bonding, and electronic properties of gallium oxide (Ga 2 O 3 ) nanofibers made by a simple and economically viable electrospinning process. The effect of processing parameters on the properties of Ga 2 O 3 nanofibers were evaluated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Thermal treatments in the range of 700-900 °C induce crystallization of amorphous fibers and lead to phase stabilization of α-GaOOH, β-Ga 2 O 3 , or mixtures of these phases. The electron diffraction analyses coupled with XPS indicate that the transformation sequence progresses by forming amorphous fibers, which then transform to crystalline fibers with a mixture of α-GaOOH and β-Ga 2 O 3 at intermediate temperatures and fully transforms to the β-Ga 2 O 3 phase at higher temperatures (800-900 °C). Raman spectroscopic analyses corroborate the structural evolution and confirm the high chemical quality of the β-Ga 2 O 3 nanofibers. The surface analysis by XPS studies indicates that the hydroxyl groups are present for the as-synthesized samples, while thermal treatment at higher temperatures fully removes those hydroxyl groups, resulting in the formation of β-Ga 2 O 3 nanofibers.