Xiaodong Lu

Amorphous silicon-assisted self-catalytic growth of FeSi nanowires in arc plasma

We report the synthesis of FeSi nanowires via a direct current arc discharge method. As material sources, the mixture of Si and Fe powders are put into a graphite crucible that acts as the anode. Free-standing FeSi nanowires are deposited on the iron wires suspended near the cathode without the designed use of any catalyst. The as-grown FeSi nanowires are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The typical size of the FeSi nanowires is 1-3 μm in length and 10-20 nm in diameter. Based on the traditional vapor-liquid-solid (VLS) growth model, a so-called amorphous silicon-assisted self-catalytic growth process is put forward to explain the growth mechanism of the FeSi nanowires. A photoluminescence emission peak with a maximum at about 600 nm is observed at room temperature. Magnetic characterization is carried out and the results show that the FeSi nanowires exhibit ferromagnetic characteristics at room temperature.

Design of GaAs solar cell front surface anti-reflection coating

Based on a variety of dielectric film materials are of different refractive rate, design anti-reflection coating structure applying on the GaAs solar cell front surface in transfer matrix method (TMM), the optical absorption effect showed by different coating structure are analyzed and evaluated. Results show that: the three-layer anti-reflection film structure composed of three different dielectric film material has a smaller reflection loss than single-layer coating and double coating in GaAs cells absorb spectrum (300 nm ~ 867 nm wavelength range), for different incident angles, the reflectivity of incident light can be reduced to less than 5%.

Preparation of SiO 2 nanowires by using carbon as reducing agent

SiO2 nanowires structures have been grown by a simple thermal evaporation method using C and SiO2 as the source materials at a relatively low. The as-synthesized products were characterized by scanning electron microscopy, electron energy-dispersive X-ray (EDX), X-ray powder diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). The products characterization indicated that the SiO2 nanowires with diameters ranging from 60nm to 120nm with a hexagonal strcture, with the length up to a few centimeters. The photoluminescence spectra of the grown products indicate excellent optical properties for the as-grown SiO2 nanowires.

S-doped SiO 2 microsphere structure prepared by thermal evaporation

S-doped SiO2 microspheres have been successfully synthesized via the thermal evaporation method using S powders as the reducing agents. The as-synthesized products have been systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscope (SEM), electron energy-dispersive X-ray (EDX) and photoluminescence (PL). The results indicate that pure S-doped SiO2 microspheres were collected at the growth temperatures of 730 °C. Furthermore, The RT PL spectral results reveal the S-doped SiO2 microspheres have a stable and strong green emission band. The products are available for the applications in optoelectronic semiconductor devices with improving performances.

Reflecting filters based on one dimensional photonic crystal with large lattice constant

We change the optical thicknesses of different layers in one dimensional photonic crystals (1DPCs) by introducing sine and cosine functions into transfer matrix method and find that the changes of 1DPCs optical thicknesses from regular periodic structures to sine and cosine function structures, will make the reflection spectrums of 1DPCs appear multiple reflection peaks and these peaks widths and positions can be easily modulated by changing the fundamental parameters of sine and cosine functions. In this paper, we use this method to design two types of narrow band reflecting filters based on 1DPCs with large lattice constant.

Preparation and characterization of Cu 2 ZnSnS 4 thin films by solvothermal method

The Cu2ZnSnS4 thin films have been deposited onto FTO glass substrates by a simple solvothermal method. The films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analyzer, and optical absorption spectroscopy technique, respectively. The influence of the annealing temperature on the structure, morphology, and composition of the films has been studied. The polycrystalline Cu2ZnSnS4 thin films crystallized in the tetragonal structure with nearly stoichiometric after annealing at 550 °C in Ar atmosphere for 1h. The analysis of the optical absorption data gave the bandgap energy to be 1.5 eV. The photoelectrochemical characterization showed that the annealed CZTS thin films behaved as p-type semiconductor photoelectrodes.

Preparation and characterization of CdIn 2 S 4 wedgelike thin films

Cadmim Indium sulfide (CdIn₂S₄) thin films composed of wedgelike crystals were prepared on fluorine-doped tin oxide substrate by a tartaric acid assisted hydrothermal method. The tartaric acid was found to play an important role in the formation of the final product. The formation mechanism of the CdIn₂S₄ film was also discussed. The optical properties and microstructure of the CdIn₂S₄ films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and UV-vis absorption spectroscopy. The results revealed that the wedgelike CdIn₂S₄ thin films were crystallized in the cubic spinel structure. The analysis of optical absorption data shows bandgap energy to be 2.46 eV which is optimal for photovoltaic applications.

Optimization of antireflective coatings to crystalline silicon solar cell

Based on varieties of dielectric film materials with different refractive rate, this paper has designed antireflective coatings to crystalline silicon solar cell front surface in transfer matrix method (TMM). The optical absorption effect showed by single, double, three layer antireflection coatings and the incident light with different angle of incidence are analyzed and evaluated. Results show that: when 360nm<;λ<;1200nm, among double layer dielectric film, the reflection loss of MgF2|Si3N4 double layer dielectric film is minimum; among three layer dielectric film, the MgF2|Al2O3|Si3N4 three layer dielectric film reflection loss is very low. In the three layer antireflection film structure and for different incident angles, the reflectivity of incident light can be reduced basically under 10%, and all regions of the spectrum absorption of the silicon material are made good use.