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GaN nanoparticles were prepared on sapphire (0001) substrates with ZnO sacrificial layers by self assembly of GaO films in their reaction with NH. ZnO sacrificial layers with different thicknesses and GaO films were deposited on sapphire substrates in turn by a radio frequency (RF) magnetron sputtering system. Nitridation of the GaO films was then carried out in a quartz tube furnace. The effect of ZnO sacrificial layer thickness on the structure and optical properties of nanoparticles prepared by RF magnetron sputtering were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoluminescence (PL). GaN nanoparticles with ZnO sacrificial layers of different thicknesses possess hexagonal wurtzite crystal structure and have a preferred orientation with c axis perpendicular to the sapphire substrates. XRD, SEM, and AFM results reveal that the better-crystallinity, uniform, and well-dispersed GaN nanoparticles (∼30 nm) without agglomeration were obtained with a ZnO sacrificial layer 300-nm thick. The PL result reveals that the optical properties of the GaN nanoparticles are improved with a ZnO sacrificial layer 300-nm thick. Therefore, we suggest that a ZnO sacrificial layer 300-nm thick is the most suitable condition for obtaining better-quality GaN nanoparticles with good luminescence performance. Moreover, the mechanism of the formation of GaN nanoparticles with ZnO sacrificial layers is also discussed. [ABSTRACT FROM AUTHOR]

Highlights • Ga 2 O 3 film with (2 ¯ 0 1) preferred orientation was sputtered on SiC crystal substrate. • After annealing at 800 °C, Ga 2 O 3 film has better crystalline quality (FWHM = 0.108°). • Based on the facile Ga 2 O 3 film, MSM deep-ultraviolet detector was fabricated. • Its responsitvity and detectivity reach 2.6 A/W and 1.6 × 1012 Jones, respectively. • The detector shows fast response characteristics with the response time of 0.26 s. Abstract As a wide-bandgap semiconductor oxide material, Ga 2 O 3 has great application prospects in various optoelectronic fields. At present, much attention has been paid to Ga 2 O 3 deep ultraviolet (DUV) detectors, in which Ga 2 O 3 films are often poor-quality poly-crystalline or expensive mono-crystalline. In this paper, Ga 2 O 3 films with highly preferred orientation were deposited on hexagonal SiC (6H-SiC) substrate by magnetron sputtering, and the as-prepared Ga 2 O 3 films were then annealed. The influences of sputtering and annealing parameters on Ga 2 O 3 films were analyzed. Finally, DUV photo-detectors based on the as-obtained Ga 2 O 3 films were fabricated. The experimental results show, when choosing optimal sputtering parameters (RF power: 120 W, gas pressure: 1.5 Pa, film thickness: 400 nm), the sputtered Ga 2 O 3 films with (2 ¯ 0 1) highly preferred orientation after annealing at 800 °C, have good crystalline quality (FWHM = 0.108°) between single-crystal and polycrystal, showing good compromise between optoelectronic characteristics and preparation cost. The fabricated metal-semiconductor-metal (MSM) DUV photodetector operated at a bias voltage of 10 V can achieve excellent comprehensive photo-detection properties for 254 nm ultraviolet light: the responsivity, detectivity and quantum efficiency are high as 2.6 A/W, 1.6 × 1012 Jones and 1265%, respectively, along with short response time of 0.26 s. [ABSTRACT FROM AUTHOR]

GaN nanowires were synthesized on sapphire substrates by chemical vapor deposition. The selective growth of GaN nanowires was obtained through an N-Ga2O3 layer prepared by radio frequency magnetron sputtering. The X-ray diffraction (XRD) and Raman measurements indicated the GaN nanowires to be all indexed to the hexagonal wurtzite structure. The photoluminescence (PL) spectra were composed of a strong UV emission peak (365nm) and a weak yellow luminescence (YL) band (~600nm). The selective growth mechanism of GaN nanowires was briefly discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] AZO thin films were prepared on a-Si films by RF magnetron sputtering. [•] AZO thin films were prepared on a-Si films with various sputtering powers. [•] The crystallinity of AZO films was markedly improved at sputtering power of 1000W. [•] Thickness of a-Si film substrate is being reduced with increasing sputtering power. [•] AZO films deposited on a-Si films are suitable for application in HJ solar cells. [Copyright &y& Elsevier]

Highlights: [•] N-doped Ga2O3 films were deposited on sapphire substrates by radio frequency magnetron sputtering. [•] The samples were annealed in N2, O2, air, respectively. [•] The influence of annealing atmosphere on the structure, morphology and transmittance was investigated. [•] Annealing in nitrogen showed smooth surface and higher transmission in visible range. [•] The red shift of the optical band gap was observed after annealing. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we studied the growth of AlN films on 6H–SiC substrates under various sputtering pressures by RF reactive magnetron sputtering at low deposition temperature (300°C). The composition, chemical structure and oxygen impurity of the deposited films were investigated by X-ray photoelectron spectroscopy (XPS). It is suggested that the Al/N ratio of the high purity film is 1.13:1 which is very close to the stoichiometric value (1:1), and a few oxygen impurities exist in the grain boundaries in the form of Al. The two-dimensional X-ray diffraction (2D-XRD) was used to study the crystal structure of the deposited films. 2D-XRD patterns indicate that a low sputtering pressure favor the growth of AlN film with c-axis oriented, and a highly c-axis oriented AlN film resemble single crystal structure was prepared at the sputtering pressure of 0.3Pa. Surface morphology of the deposited films were investigated by SEM and AFM. The images show that the surface morphology of the films with (0002) preferred orientation present a pebble-like structure, and the grain size and surface roughness of the films decrease with increasing the sputtering pressure. [Copyright &y& Elsevier]

Abstract: In this paper, c-axis oriented AlN films were prepared on sapphire substrate by RF reactive magnetron sputtering at various deposition temperatures (30–700°C). The influences of deposition temperature on the chemical composition, crystalline structure and surface morphology of the AlN films were systematically investigated. The as-deposited films were characterized by X-ray photoelectron spectroscopy (XPS), two-dimensional X-ray diffraction (2D-XRD) and atomic force microscopy (AFM). The experimental results show that it can be successfully grown for high-purity and near-stoichiometric (Al/N=1.12:1) AlN films except for the segregation of a few oxygen impurities exist in the form of Al–O bonding. The chemical composition of as-deposited films is almost independent of substrate temperature in the range of 30–700°C. However, the crystalline structure and surface morphology of the deposited AlN films are strongly influenced by the deposition temperature. The optimum deposition temperature is 300°C, giving a good compromise between crystalline structure and surface morphology to grow AlN films. [Copyright &y& Elsevier]

Abstract: ZnO thin films were epitaxially grown on sapphire (0001) substrates by radio frequency magnetron sputtering. ZnO thin films were then annealed at different temperatures in air and in various atmospheres at 800°C, respectively. The effect of the annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films are investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL). A strong (002) diffraction peak of all ZnO thin films shows a polycrystalline hexagonal wurtzite structure and high preferential c-axis orientation. XRD and AFM results reveal that the better structural quality, relatively smaller tensile stress, smooth, uniform of ZnO thin films were obtained when annealed at 800°C in N2. Room temperature PL spectrum can be divided into the UV emission and the Visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the Visible broad band emission can be ascribed to the deep level emissions (DLE). By analyzing our experimental results, we recommend that the deep-level emission correspond to oxygen vacancy (VO) and interstitial oxygen (Oi). The biggest ratio of the PL intensity of UV emission to that of visible emission (I NBE/I DLE) is observed from ZnO thin films annealed at 800°C in N2. Therefore, we suggest that annealing temperature of 800°C and annealing atmosphere of N2 are the most suitable annealing conditions for obtaining high quality ZnO thin films with good luminescence performance. [Copyright &y& Elsevier]