Jinliang Yan

ZnO/Ag/ZnO multilayer films deposited at room temperature

Transparent conductive ZnO/Ag/ZnO multilayer films were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of silver at room temperature. A silver film with nanoscale thickness was used as intermediate metallic layers. The crystal structure of the ZnO/Ag/ZnO film was analyzed by X-ray diffraction. The electrical property of the ZnO/Ag/ZnO film was investigated by a linear array four-point probe. The transmittance spectra of the ZnO/Ag/ZnO films were measured using spectrophotometer. A strong ZnO (002) peak is seen for ZnO/Ag/ZnO film, indicating polycrystalline nature and wurtzite structure of ZnO film. Silver has (111) orientation, addition of underlayer ZnO enhances the polycrystallinity of silver layer in ZnO/Ag/ZnO multilayer film. The transmittance decreases in the short wavelength as well as in the long wavelength regions as the thickness of the silver layer is increased. The peak transmittance shifts toward the long wavelength region when the thickness of the two ZnO layers is increased. The electrical and optical properties of the ZnO/Ag/ZnO films depend strongly on the silver film thickness. ZnO/Ag/ZnO multilayer films having high transmittance of 92.5% and low sheet resistance of 4.2Ω/sq. are successfully fabricated and can be reproduced by controlling the preparation process parameters properly.

Polarizer Made of Anodic Alumina Film

A theoretical evaluation has been made of the optical loss of anodic alumina film with implanted metal columns. It has been shown that micro-columns arranged in the alumina film give rise to an optical loss that strongly depends on the direction of polarization, exhibit a prominent anisotropy in the optical loss near the infrared wavelength. The porous alumina film was prepared by anodizing aluminum, and then silver was electrodeposited into pores of alumina film by using alternating current. Silver nanowires are parallel to each other in the pores of the alumina film. Spectrophotometer measurements show that anodic alumina film with silver nanowire arrays has an excellent polarization property in near infrared region. An extinction ratio of 30 dB and average insertion loss of 0.8 dB in the wavelength range 1-2.2 mum were obtained. The anodic alumina film with silver nanowires can be used as a novel polarizer

Spectral investigation of porous anodic alumina film

Nanopore arrays were fabricated by self-organized anodization on aluminum. A two step anodization process was used to oxidize aluminum in H2SO4 solution. Hexagonally ordered pore array films were obtained by dissolving the remained aluminum base of anodic alumina in saturated HgCl2 solution. Scanning electron microscopy and X-ray Diffraction were used to investigate the morphology and crystal structures of the porous anodic alumina films. An investigation was made on the optical transmission, optical absorption and photoluminescence of the porous anodic alumina films. The results show that the highly ordered anodic porous alumina films are amorphous. The transmission spectra and absorption spectra of porous anodic alumina films abruptly curve at wavelength of 360nm, the optical transmission increases at wavelength more than 360nm, the optical absorption increases at wavelength less than 360nm. The photoluminescence intensity and peak position of the porous anodic alumina films depend strongly on the excitation wavelength, there is a wide blue photoluminescence band in the wavelength range of 340- 600nm.

Optical properties of porous anodic alumina films implanted with ZnO nanoparticles

Porous anodic alumina (PAA) films with highly ordered pore arrays were prepared by a two step anodization process in 0.3M oxalic acid solution at 0°C. ZnO nanoparticles were loaded into the nanopores of PAA films by soaking the PAA films in an aqueous solution of zinc acetate and then annealing them at 500°C. The PAA films and ZnO/PAA composites were characterized by scanning electron microscope, X-ray diffraction, ultraviolet-visible spectrophotometer and fluorescent spectrometer. The highly ordered PAA films are amorphous, the PAA films have a high optical transmissivity in visible range and a wide blue photoluminescence band in the wavelength range of 350~550nm. The photoluminescence intensity and peak position depend strongly on the excitation wavelength. ZnO nanoparticles loaded into PAA films display a pure wurtzite ZnO phase, the average diameter of ZnO particles is 10.8nm. The transmissivity of PAA films declines after ZnO is loaded in. The photoluminescence of ZnO/PAA films exhibits intense and broad emission spectra in the wavelength range of 350-600nm. There is only one strong photoluminescence peak at 430nm when excited at 340nm wavelength, the photoluminescence peak divides into two peaks of 410nm and 460nm while excited at 380nm wavelength. The oxygen vacancies, F+ centres, are responsible for the photoluminescence of ZnO nanoparticles loaded into PAA films.

Theory and simulation of MEMS deformable mirror

A novel MEMS deformable mirror was proposed and characterized. Actuator deflection was simulated using one dimensional electromechanical model. The diaphragm was modeled as a double cantilever beam, with a gap-dependent electrostatic actuating force. The effect of the structural parameters and actuated voltages on the deflection of the actuator was closely studied. A lumped parameter model for predicting the reset transient motion of the actuator, taking into account tensile forces and viscous air damping via squeeze film theory, was used to determine the reset time. The results show that the elastic diaphragm thickness, the elastic diaphragm length and gap spacing have a strong effect on the deflection, the actuator displays typical nonlinear deflection versus voltage characteristics and electromechanical instability at elevated voltages. The reset transient motion of the actuator is an exponential decay oscillation line, the reset time is about 0.14μs.