Selective Area Growth of Gallium Oxide Nanowires on Gold Patterned Gallium Arsenide Using Implantation-assisted Technique

In this paper, the selective area synthesis of gallium oxide (Ga2O3) nanowires on gold patterned gallium arsenide (GaAs) substrate by ion implantation will be reported. The GaAs substrate was first treated with implantation of acetylene ions, nitrogen ions or nitrogen and oxygen co-implantation, followed by coating the surface with a gold film of 40nm in thickness. After rapid thermal annealing at 950oC for 30 seconds, Ga2O3 nanowires were found on the gold patterned surface. The Ga2O3 nanowires with diameters of 50-500nm were examined and characterized by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy and cathodoluminescence spectroscopy. Nanoparticles of gold were found at the tip of the nanowires, suggesting that a vapor-liquid-solid mechanism was involved. However, the fact that other implanted species such as argon and oxygen would not lead to the formation of Ga2O3 nanowires also suggests that the nitrogen and carbon play an important role as a catalyst. The implanted nitrogen forms intermediate gallium nitride nano-grains, which may in term lead to the formation of nano-grains of Ga2O3 upon reacting with ambient oxygen. These Ga2O3 nano-grains then act as a growth template for nanowires. Carbon has previously been reported to be a reduction agent for the formation of group III sub-oxides. Such sub-oxides provide the vapor source for the growth of nano-materials through further oxidation. In addition, when we annealed the implanted samples in an ambient with oxygen concentration higher than 1%, a thick Ga2O3 film formed and nanoribbons was inhibited.