Usage of Simulated Annealing Algorithm in Design of Optical Thin Film

Simulated annealing algorithm is a mathematic model,which imitates the physical process of annealing. And optical thin film is widely used in many industry.Its design is difficult and can be regarded as an optimization problem.In this paper,we use the simulated annealing algorithm to design an edge filter,which is composed of 20 dielectric thin film layers with TiO2 and SiO2.The simulated annealing algorithm is a very robust algorithm for optical thin film design.

Microstructure Control of Nanoporous Silica Thin Film Prepared by Sol-gel Process

Nanoporous silica films were prepared by sol-gel process with base, acid and base/acid two-step catalysis.Transmission electron microscope （TEM） and particle size analyzer were used to characterize the microstructure and the particle size distribution of the sols. Scanning electron microscopy （SEM）, atomic force microscopy （AFM） and spectroscopic ellipsometer were used to characterize the surface microstructure and the optical properties of the silica films. Stability of the sols during long-term storage was investigated. Moreover,the dispersion relation of the optical constants of the silica films, and the control of the microstructure and properties of the films by changing the catalysis conditions during sol-gel process were also discussed.

Design of non-polarizing thin film edge filters

The separation between s- and p-polarization components invariably affects thin film edge filters used for tilted incidence and is a difficult problem for many applications, especially for optical communication. This paper presents a novel design method to obtain edge filters with non-polarization at incidence angle of 45°. The polarization separation at 50% trans-mittance for a long-wave-pass filter and a short-wave-pass filter is 0.3 nm and 0.1 nm respectively. The design method is based on a broadband Fabry-Perot thin-film interference filter in which the higher or lower interference band at both sides of the main transmittance peak can be used for initial design of long-wave-pass filter or short-wave-pass filter and then can be refined to reduce the transmittance ripples. The spacer 2H2L2H or 2L2H2L of the filter is usually taken. Moreover, the method for expanding the bandwidth of rejection and transmission is explained. The bandwidth of 200 nm for both rejection region and transmission band is obtained at wavelength 1550 nm. In this way, the long-wave-pass and short-wave-pass edge filters with zero separation between two polarization components can easily be fabricated.

The third-order optical nonlinearity of the stainless steel doped SrTiO_3 thin film grown by L-MBE

Stainless steel-doped SrTiO3 thin films were fabricated by laser molecular beam epitaxy (L-MBE). Nonlinear optical property of the thin film was measured by the single beam Z-scan technique at the wavelength of 532 nm. Two two-phonon absorption coefficient and nonlinear refractive index were determined to be 9.37 x 10-7 m/W and 1.55 x 10-6 esu, respectively. The merit figure T was calculated to be 1.8, satisfying condition T < 1 for an optical switch. The thin film has a very promising prospect for the applications in optical device.

Semiconductor performance of rare earth gadolinium-doped aluminum–zinc oxide thin film

Rare earth element gadolinium-doped aluminum–zinc oxide（Gd–AZO） semiconductor thin film material was deposited on both silicon and glass substrate by radio frequency（RF） sputtering at room temperature.Electrical properties and microstructure of Gd–AZO thin film were mainly modulated by altering O2 partial pressure（OPP） during the RF sputtering process.Scanning electron microscope（SEM） and X-ray diffraction（XRD） test were carried out to uncover the microstructure variation trend with the sputtering OPP,and amorphous structure which is beneficial to large mass industry manufacture was also demonstrated by the XRD pattern.Transmittance in visible light spectrum implies the potential application for Gd–AZO to be used in transparent material field.Finally,bottom gate,top contact device structure thin film transistors（TFTs） with Gd–AZO thin film as the active channel layer were fabricated to verify the semiconductor availability of Gd–AZO thin film material.Besides,the Gd–AZO TFTs exhibit preferable transfer and output characteristics.

Low substrate temperature deposition of transparent and conducting ZnO:Al thin films by RF magnetron sputtering

Transparent and conducting Al-doped ZnO（ZnO：Al） films were prepared on glass substrate using the RF sputtering method at different substrate temperatures from room temperature（RT） to 200 ℃. The structural,morphological, electrical and optical properties of these films were investigated using a variety of characterization techniques such as low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy（XPS）, field-emission scanning electron microscopy（FE-SEM）, Hall measurement and UV–visible spectroscopy. The electrical properties showed that films deposited at RT have the lowest resistivity and it increases with an increase in the substrate temperature whereas carrier mobility and concentration decrease with an increase in substrate temperature. Low angle XRD and Raman spectroscopy analysis reavealed that films are highly crystalline with a hexagonal wurtzite structure and a preferred orientation along the c-axis. The FE-SEM analysis showed that the surface morphology of films is strongly dependent on the substrate temperature. The band gap decreases from 3.36 to 3.29 e V as the substrate temperature is increased from RT to 200 ℃. The fundamental absorption edge in the UV region shifts towards a longer wavelength with an increase in substrate temperature and be attributed to the Burstein-Moss shift. The synthesized films showed an average transmission（〉 85%） in the visible region, which signifies that synthesized ZnO：Al films can be suitable for display devices and solar cells as transparent electrodes.

The effect of complexing agent on crystal growth, structure and properties of nanostructured Cu_(2-x)S thin films

Thin films of Cu2 x S（x = 0, 1） were deposited on self-assembled, monolayer modified substrates in the copper–thiosulfate system with various concentrations of ethylene diamine tetraacetic acid（EDTA） at a low temperature of 70 8C. The thin films were characterized by means of X-ray diffraction（XRD）, X-ray photoelectron spectroscope（XPS）, field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM）. The optical and photoelectrochemical（PEC） properties of the Cu2 x S semiconductor films were investigated by ultraviolet–visible（UV–vis） absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2 x S nanocrystals formation and growth. The compositions of the Cu2 x S nanocrystals varied from Cu2S（chalcocide） to Cu S（covellite） through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2 x S films. The growth mechanisms of Cu2 x S nanocrystals with different EDTA concentrations are proposed and discussed in detail.

Spray pyrolysis of tin selenide thin-film semiconductors:the effect of selenium concentration on the properties of the thin films

Thin films of tin selenide（Sn_xSe_y） with an atomic ratio of r =[y/x]= 0.5,1 and 1.5 were prepared on a glass substrate at T = 470℃using a spray pyrolysis technique.The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride（SnCl_4·5H_2O） and selenide acide（H_2SeO_3）.The prepared thin films were characterized by X-ray diffraction（XRD）,scanning electron microscopy,scanning tunneling microscopy,scanning helium ion microscopy,and UV-vis spectroscopy.The photoconductivity and thermoelectric effects of the Sn_xSe_ythin films were then studied.The Sn_xSe_y thin films had a polycrystalline structure with an almost uniform surface and cluster type growth.The increasing atomic ratio of r in the films,the optical gap,photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV,0.01 to 0.31 and -26.2 to—42.7 mV/K （at T = 350 K）,respectively.In addition,the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe_2 phases.

Chemical Bath Co-deposited ZnS Film Prepared from Different Zinc Salts: ZnSO_4—Zn(CH_3COO)_2, Zn(NO_3)_2—Zn(CH_3COO)_2,or ZnSO_4—Zn(NO_3)_2

ZnSO4-Zn（CH3COO）2, Zn（NO3）2-Zn（CH3COO）2, ZnSO4-Zn（NO3）2, ZnSO4, Zn（NO3）2 or Zn（CH3COO）2 have been used as zinc sources to prepare ZnS thin films by chemical bath deposition and co-deposition methods. Zn（NO3）2 or/and Zn（CH3COO）2 is/are favorable for cluster by cluster deposition process while ZnSO4 favors ion by ion deposition process regardless of concentration ratios of ZnSO4. However, Zn（NO3）2 affects the nucleation density of ZnS nuclei on the substrate. ZnS thin films deposited from ZnSO4-Zn（CH3COO）2 are not only more homogeneous and compact, but also have higher growth rate and adhesion on to the glass substrate. The cubic ZnS films are obtained after only single deposition. The average transmission of films from S6, S7, S8, S9 and S1 for 2 and 2.5 h is greater than 85% in visible region. Compared with the film from S6 （112 nm）, the film from S7 is not only thicker （125 nm）, but also more transparent. The band gaps of the films deposited from S6,S7, S8, S9 and S1 for 2 and 2.5 h range from 3.88 to 3.98 eV. The effects of anions from different zinc salts are discussed in detail.

Optimization of SnS active layer thickness for solar cell application

This work presents a comparative study of n-SnS and p-SnS active layers for increased solar cell efficiency. Tin sulphide thin films of various thicknesses having p-type and n-type conductivity were fabricated by thermal evaporation. Both type of films had the same（113） orientation of the crystal planes with a constant tensile strain of ~ 0.003 and ~ 0.011, respectively. The persistent photocurrent was observed in all n-SnS and p-SnS samples with the current＇s time decay constant decreasing with increasing film thickness. Hole mobility of thicker p-SnS films was found to be greater than the electron mobility in n-SnS samples, with mobility（both hole and electron） showing an increasing trend with film thickness. The optimum absorber layer thickness for both p-and n-SnS layers should have a high value of diffusion length for a given absorption coefficient and band-gap.