Research paperRed-light emission of Li-doped Ga2O3 one-dimensional nanostructures and the luminescence mechanism
Graphical abstract
Introduction
Compared to conventional bulk and thin film semiconductors, single crystal and one-dimensional semiconductor nanostructures have attracted great attention due to their size confinement and increased surface to volume ratio resulting in excellent optical, electrical and chemical properties. Gallium oxide (Ga2O3) is promising nanometer semiconductor oxides for optoelectronic application due to its wide band gap (4.8–5.1 eV) and vacancy defects [1], [2], [3], [4], [5]. Owing to the reasonable electrical conductivity, and high thermal and chemical stability, the doped Ga2O3 one-dimensional (1D) nanostructures could exhibit excellent photoelectric properties [6], [7]. Many studies have produced Ga2O3 1D nanostructures doped with different elements, such as rare earths, transition metals, as well as isoelectronic dopants [8], [9], [10], [11], [12], [13]. Due to the defect structure in Ga2O3 [4], [14], [15], and the existence of many intrinsic donor defects in Ga2O3 materials, the acceptor level of Ga2O3 is generally deep. That makes it not easy for holes to enter the valence band. Thus it is sometimes difficult to achieve p-type doping, which restricts the development of Ga2O3 devices. However, recent reports [8], [9], [11] have proved that doping metals could help Ga2O3 become p-type, such as Zn, Mg and Cu, etc. In addition, Gonzalo [13] has studied the luminescence and structure of Ga2O3 nanowires after doping transition metal ions. Pang [16] has studied the Li+ doping to optimize the optoelectronic properties of Ga2O3: Dy3+. Since defects in the Ga2O3 before and after doping are different, it exhibits different optical properties. Therefore, optical characterization is a very effective means of assessing the change in properties after doping.
In this work, Li-doped Ga2O3 one-dimensional (1D) nanostructures were synthesized by a thermal evaporation method. The morphology of the samples was characterized by scanning electron microscopy (SEM). In addition, the room-temperature Raman spectrum of Li-doped Ga2O3 1D nanostructures was used to confirm whether the Li ions were incorporated into the prepared product. And another, Photoluminescence (PL) measurements were carried out to gain the light emission characteristics of the prepared Li-doped Ga2O3 1D nanostructures.
Section snippets
Experimental
Li-doped Ga2O3 1D nanostructures were fabricated by thermal evaporation in ample oxygen atmosphere. The experimental system consists of a horizontal tube furnace, two ceramic boats and temperature control system. Specifically, pure gallium oxide powder, lithium hydroxide powder and metallic gallium were mixed in a ceramic boat at a weight ratio of 4:1:4. To help the formation of Li-doped Ga2O3 1D nanostructures, an appropriate amount of carbon powder was added to the mixtures. Two silicon
Structural properties
The sample prepared at the growth temperature of 1000 °C shown in the SEM image of Fig. 1(a) has two nanostructures, nanowires and nanoribbons. The average diameter of the Li-doped Ga2O3 nanowires are about 60 nm and length up to several tens of microns. A nanoribbon is shown in Fig. 1(b), which is relatively uniform and relatively flat, and the ribbon presents dimensions in the range of several microns wide and several tens of microns long. In order to precisely define the chemical composition
Conclusion
Li-doped Ga2O3 1D nanostructures have been successfully synthesized through thermal evaporation process. Raman analysis shows that the samples have good crystallinity. Due to the doping of Li ions, the Raman spectrum of the Li-doped Ga2O3 1D nanostructures has a slight red-shift in the low wavenumber sections compared to the “undoped”, and the PL peaks of the Li-doped Ga2O3 are blue-shifted in the blue-green emission range. Furthermore, the Li-doped Ga2O3 1D nanostructures not only have a blue
Declaration of interests
The authors declared that there is no conflict of interest.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (No. 61601397, No. 61805209, and No. 60277023), and Graduate Innovation Foundation of Yantai University (GIFYTU).
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