GaOOH, and beta- and gamma-Ga2O3 nanowires: preparation and photoluminescence

A composite methodology using laser ablation followed by a solution refluxing process was demonstrated to prepare GaOOH and (beta-, gamma-) Ga2O3 nanowires, where GaOOH and gamma-Ga2O3 nanowires were prepared for the first time. The CTAB surfactant and PVP polymer facilitated the nucleation and growth of GaOOH nanorods, and played different roles in selectively controlling the growth rates of different facets. In the PVA/CTAB-assisted reaction, a high aspect ratio (of at least 200) of GaOOH nanowires was approached. The calcination of GaOOH nanowires at a temperature of 500 degrees C (6 h) transformed them into gamma-Ga2O3 nanowires and converted them further into beta-Ga2O3 nanowires at 750 degrees C (18 h). Photoluminescence measurements were conducted at room temperature for the GaOOH and (beta-, gamma-) Ga2O3 nanowires using a high resolution synchrotron X-ray source. The blue emissions from the GaOOH and (beta-, gamma-) Ga2O3 nanowires were resolved into a few sharp peaks, and may provide a valuable reference for further understanding the PL mechanisms. Although luminescence spectra of the GaOOH and gamma-Ga2O3 nanowires were recorded for the first time, the similar optical band gap and emission contour observed for beta-Ga2O3 nanowires suggests that the optical behavior of GaOOH and gamma-Ga2O3 nanowires are likely to closely follow the PL mechanisms of beta-Ga2O3 nanowires.