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We studied the growth process of nanocrystalline ZnO which grown in amorphous ZnO by photoluminescence (PL). In this process, we found a new visible emission band, the visible emission intensity increased quickly at first, then decreased exponentially, while the peaks energy has a red shift from 583nm to 615nm along with the increasing reaction temperature. The results indicate this visible emission...
A novel type of GaN substrate for light emitting devices with a highly polarized output using metal-dielectric composite subwavelength grating structure is proposed. Characteristics of both optical transmission and polarization extinction ratio of the polarized GaN-based LED with a double-layer grating structures are investigated. It is found that both TM transmission (TTM) and the extinction ratio(ER)...
Using the magnetron sputtering technology, high quality Al2O3-based textured ZnO thin films (Al2O3/ZnO) which can be applied to solar cells' light trapping effect were fabricated by controlling the preparation parameters properly. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) results show that O2 /(Ar+O2) flow ratio has great influence on Al2O3/ZnO films surface morphology during...
The feasibility of THz oscillations in a GaN-based planar nanoscale unipolar diode, or a self-switching device (SSD), is analyzed using Monte Carlo simulations. The origin of THz oscillations is contributed to Gunn-effect. The dependence of the Gunn oscillations on geometric parameters and bias conditions has been studied. By using proper parameters, the oscillation frequency can reach 0.6 THz. Moreover,...
The effect of carrier gas on thick GaN film grown by hydride vapor phase epitaxy on (0001) sapphire substrate has been studied by double crystal X-ray diffraction (DCXRD), polarizing microscope and field emission scanning electron microscope (FE-SEM). H2, as carrier, is propitious to two-dimension growth pattern of GaN film but causes production of more defects and impurities. N2, as carrier, weakens...
Using first-principles total energy calculations, we have studied the structural and electronic properties of GaNxAs1-x alloys within density-functional theory (DFT) framework. The validity of Local density approximation (LDA) and generalized gradient approximation (GGA) has been demonstrated by the calculations of lattice parameters and band-gap bowing. The results show that LDA is relatively more...
The stabilities of the doped configurations and the ferromagnetic ordering behaviours in ZnO system are studied systematically by calculating the total energies of the ferromagnetic and antiferromagnetic state based on density function theory. The doping atoms tend to align closely each other to hold the most stable configuration. The weak ferromagnetic properties only exists in the case when the...
A simple microwave reaction method without using additives was employed to synthesize ZnO microcrystals with controllable morphology. Zinc acetate dehydrate was selected as reactants and ethylene glycol-water was solvents. Peanutlike ZnO built up by short nanorods, multi-sphere aggregations, spherelike microcrystals covered by ZnO nanoparticles, and spinous morphology mixed with flake like ZnO were...
Prepared a-SiC thin films with plasma enhanced chemical vapor deposition (PECVD) at low temperature (135°C), by using CH4, H2, SiH4 and B2H6. And with Raman spectroscopy, ellipsometry, absorption spectroscopy and other equipment to demonstrate the film characteristics such as structural characteristics, growth rate characteristics, band gap and refractive index spectra. The results show that we facbricate...
ZnO bulk material (bandgap 3.26 eV) was reduced in size via a top-down wet-chemistry synthesis process into colloidal nanoparticles that were then coated with polyvinyl-alcohol (PVA). When the nanoparticles were excited at 340 nm, strong UV emission at 377 nm was observed, and parasitic green emission (510 nm) which normally appears in ZnO nano-material was suppressed. Quantum confinement effects...
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