The growth of ultralong and highly blue luminescent gallium oxide nanowires andnanobelts, and direct horizontal nanowire growth on substrates

Abstract

We report the growth of ultralongβ-Ga2O3 nanowires and nanobelts on silicon substrates using a vapor phase transport method. Thegrowth was carried out in a tube furnace, with gallium metal serving as the gallium source.The nanowires and nanobelts can grow to lengths of hundreds of nanometers and evenmillimeters. Their full lengths have been captured by both scanning electronmicroscope (SEM) and optical images. X-ray diffraction (XRD) patterns andtransmission electron microscope (TEM) images have been used to study the crystalstructures of these nanowires and nanobelts. Strong blue emission from these ultralongnanostructures can be readily observed by irradiation with an ultraviolet (UV)lamp. Diffuse reflectance spectroscopy measurements gave a band gap of 4.56 eVfor these nanostructures. The blue emission shows a band maximum at 470 nm.Interestingly, by annealing the silicon substrates in an oxygen atmosphere to form a thickSiO2 film, andgrowing Ga2O3 nanowires over the sputtered gold patterned regions, horizontalGa2O3 nanowiregrowth in the non-gold-coated regions can be observed. These horizontal nanowires can grow to as longas over 10 µm in length. Their composition has been confirmed by TEM characterization. This representsone of the first examples of direct horizontal growth of oxide nanowires on substrates.