Preparation and characteristics of ultra-wide Ga<sub>2</sub>O<sub>3</sub> nanoribbons up to millimeter-long level without catalyst

Abstract

<sec>Gallium oxide (Ga<sub>2</sub>O<sub>3</sub>) single crystal nanoribbons have the potential applications in electronic devices due to their unique properties. However, the current small surface area makes the fabrication of device based on this nano-material very complex and challenging, and the introduction of catalyst also makes the growth process of Ga<sub>2</sub>O<sub>3</sub> nanomaterial complicated and hard to control. Therefore, it is very important to study the growth method and physical mechanism of Ga<sub>2</sub>O<sub>3</sub> nanoribbon with the larger surface area without catalyst. </sec><sec>In this paper, the carbothermal reduction method is used to grow the Ga<sub>2</sub>O<sub>3</sub> nanomaterial. In this paper, the gallium oxide powder mixes with the carbon nanotubes at a mass ratio of 1:1.5 without the catalyst, and then they are put into a high temperature diffusion furnace for the growth of Ga<sub>2</sub>O<sub>3</sub> nanomaterials with different structures on silicon-based substrates by controlling the reaction temperature. In this paper, it is found that the reaction temperature directly affects the diameter and ratio of gallium oxide nanostructures. The reason is that the bonding energy of gallium oxide crystal is different in different crystal directions which leads to the different growth speed. The interface energy along the growth direction is the smallest and the growth speed is the fastest, while the growth speed along the vertical direction is slow. Finally, the crystal gradually grows into nanoriband, nanometer sheet and other structures. </sec><sec> In addition, the ultra-wide β-Ga<sub>2</sub>O<sub>3</sub> single crystal nanobelt up to the millimeter level was prepared in this paper. This nanobelt’s lateral dimension is observed to reach 44.3 μm under the scanning electron microscope (SEM), and the transmission electron microscope (TEM) is used to confirm that the nanoribbons have a single crystal structure. Further, Raman spectroscopy (Raman) shows that the β-Ga<sub>2</sub>O<sub>3</sub> nanoribbons grown by this method have the smaller strain and the lower defect density. Additionally, the room temperature photoluminescence spectrum (PL) test shows that the gallium oxide nanoribbon emits a stable and high-brightness blue light at 425 nm at the excitation wavelength of 295 nm. This growth method can provide a useful way for the preparation of device-level gallium oxide nanoribbons in the future. </sec>