Huizhao Zhuang

Effects of ZnO buffer layers on the fabrication of GaN films using pulsed laser deposition

GaN thin films were deposited on Si (111) substrates using ZnO buffer layers by pulsed laser deposition of a GaN target in a nitrogen atmosphere. High-quality GaN thin films were obtained after annealing at 950 °C for 15 min in a NH3 atmosphere. The crystalline quality, composition, and surface morphology of the films were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy. Through analysis of the measured results, a conclusion was drawn that ZnO buffer layers and their crystalline quality affected the structural properties (crystalline quality, composition, and surface morphology) of GaN films. Crystalline ZnO buffer layers improved nucleation and growth of GaN films. Zn–O bonds are destroyed when the GaN films are annealed in ammonia (NH3) ambience; a few O and Zn atoms depart from their positions, while N and Ga atoms fill in the empty positions and form a hexagonal structure of a special component. The structure is propitious to the epitaxial growt...

Synthesis of Large-scale GaN Nanowires by Ammoniating Ga2O3/V Films

Abstract Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.

FORMATION OF GaN FILM BY AMMONIATING Ga2O3 DEPOSITED ON Si SUBSTRATE WITH ELECTROPHORESIS

The gallium nitride (GaN) films have been successfully fabricated on silicon (111) substrates through ammoniating Ga2O3 films deposited by electrophoresis. The structure and composition of the formed films were characterized by Fourier transform infrared (FTIR) transmission spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that the films formed in this study are polycrystalline GaN with hexagonal wurtzite structure.

Preparation and properties of GaN nanostructures by post-nitridation technique

Abstract Nanostructure GaN films were prepared by post-nitridation technique. The morphology and structure of GaN nanowires are investigated by using transmission electron microscopy and scanning electron microscopy. The growth mechanism of the GaN nanowires is unlikely to be controlled by the well-known vapor–liquid–solid mechanism, vapor–solid phase was involved in the growth of GaN nanostructures. A strong blue photoluminescence is observed for room temperature measurement.

Influence of Mg Doping on GaN Nanowires

Magnesium-doped GaN nanowires with different dopant concentrations are synthesized by ammoniating Ga(2)O(3) thin films doped with Mg at 900 degrees C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and room-temperature photoluminescence (PL) are employed to characterize the influences on the morphology, structure, crystallinity, and optical properties of Mg-doped GaN nanowires. The results demonstrate that the nanowires are single-crystalline with hexagonal wurzite structure. GaN nanowires doped with 5 atom % of Mg have the best morphology and crystallinity with a single-crystalline structure, and at this composition the PL spectrum with the strongest UV peak is observed. The growth mechanism of crystalline GaN nanowires is discussed briefly.

Structure and luminescence of GaN films by sputtering post-annealing-reaction technique

Abstract Gallium nitride (GaN) films were prepared on quartz substrates by sputtering post-annealing-reaction technique. The sputtered Ga 2 O 3 films were used as a precursor for GaN growth. X-ray diffractometer, X-ray photoelectron spectroscopy and TEM measurement results indicate that the obtained GaN films are polycrystalline films with hexagonal structure, which consist of single-crystalline nanorods. A strong blue photoluminescence located at 458 nm and a UV photoluminescence located at 370 nm is observed at room temperature.

Synthesis and properties of novel liquid-medicine-filter shaped ZnO nanostructures.

Liquid-medicine-filter shaped ZnO nanostructures have been synthesized on Al2O3-coated Si (111) substrates by chemical vapor deposition method (CVD) at 1050 °C. Every liquid-medicine-filter shaped ZnO nanostructure is made up of one nanorod and two nanowires at the ends. The liquid-medicine-filter shaped ZnO nanostructures are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS) photoluminescence (PL). The results indicate that the liquid-medicine-filter shaped ZnO nanostructures are wurtzite hexagonal structure and the growth direction is [0001]. The liquid-medicine-filter shaped ZnO nanostructures became the new member of ZnO nanostructures for the novel configuration. PL reveals ultraviolet (UV) emission at 384 nm and a broad emission peak at 540 nm. These novel liquid-medicine-filter shaped ZnO nanostructures will provide an improvement for electronic and optical devices. The pre-prepared Al2O3 film on the Si (111) substrate solves the troublesome lattice mismatch problem between the Si substrate and ZnO, and makes the growth of liquid-medicine-filter shaped ZnO nanostructures more effective. In addition, the effect of screw dislocation and polar surfaces in understanding crystal growth mechanisms in nanometer scale were also provided.

Effect of substrate temperature on microstructural and optical properties of ZnO films grown by pulsed laser deposition

Abstract ZnO thin films were deposited on n-Si (111) at various substrate temperatures by pulsed laser deposition (PLD). X-ray diffraction (XRD), photoluminescence (PL), Fourier transform infrared spectrophotometer (FTIR), and scanning electron microscopy (SEM) were used to analyze the structure, morphology, and optical property of the ZnO thin films. An optimal crystallized ZnO thin film was obtained at the substrate temperature of 600°C. A blue shift was found in PL spectra due to size confinement effect as the grain sizes decreased. The surfaces of the ZnO thin films were more planar and compact as the substrate temperature increased.

Synthesis of GaN films on porous silicon substrates

Abstract A novel and simple method was employed to synthesize GaN films on porous silicon (PS) substrates. GaN films were obtained through the reaction between NH 3 and Ga 2 O 3 films deposited on the substrates with magnetron sputtering. Since GaN and PS are all good materials for luminescence, it is expected to obtain some new properties from GaN on PS. The samples were analyzed with X-ray diffraction (XRD) to identify crystalline structure. Fourier transmit infrared (FTIR) spectrum was used to analyze the chemical state of the samples. The films were observed with scanning electron microscopy (SEM) and were found to consist of many big crystal grains. Photoluminescence (PL) spectrum was used to illuminate the optical property of the GaN films.

Investigation of preparation and characterization of GaN films on sapphire (0001) substrates

Gallium nitride (GaN) films were prepared on sapphire (0001) substrates by post-nitridation technique. XRD, XPS, and TEM measurement results indicate that the polycrystalline GaN with hexagonal wurtzite structure was successfully grown. Intense room-temperature photoluminescence peaked at 466 nm of the films is observed.