Effect of Film Thickness on Properties of a-Si∶H Films

The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.     

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin(II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2 :F thin films were deposited at a 350 C pending time(5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9( cm)1for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.     

Optical Constants and Structure of ZnO Films by Radio Frequency Magnetron Sputtering

ZnO films are deposited on glass slides by radio frequency（RF） magnetron sputtering under different powers. The polycrystal structures and surface morphologies of the film are investigated. The optical transmission spectra for the ZnO films are measured within the range from 300 nm to 800 nm. The optical constants and thickness of the films are determined using a nonlinear programming method suggested by Birgin et al. The band gap of the film increases with reducing the nano-size of the film grains. The packing density of the films can be improved by reducing the RF power.     

Recent Advances in ZnO Films Prepared by Pulsed Laser Deposition

Pulsed laser deposition （PLD） is emerging as the most rapid and efficient technique for fabricating the many compound films. ZnO thin films can be prepared under various deposition conditions by PLD. The effects of various substrate temperature, oxygen partial pressure, annealing temperature, substrate, buffer layers thickness and film thickness on micro-structural, optical and electrical properties of ZnO films grown by PLD technology are reviewed. ZnO films with special function can grow under proper conditions by PLD.     

Influence of substrate temperature on the deposition and structural properties of μc-Si: H thin films fabricated with VHF-PECVD

With in situ optical emission spectroscopy (OES) diagnosis on VHF-generated H₂+SiH₄ plasmas, and with the measurements of deposition rate and structure of μc-Si: H thin films fabricated with VHF-PECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si: H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature, the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for (μc-Si: H thin films deposition under our current growth system is about 210 °C, at which deposition rate 0.8 nm/s of μc-Si: H thin film with Xc?60% and d?9 nm can be obtained.     

Dependence of Threshold Voltage of a-Si:H TFT on a-SiNx:H Film^①

The relation between threshold voltage for hydrogenated amorphous silicon thin film transistors(a-Si:HTFTs)and deposition conditions for hydrogenated amorphous silicon nitride(a-SiNx:H)films is investigated.It is observed that the threshold voltage,Vth,of a-Si:HTFT increases with the increase of the thickness of a-SiNx:H film,and the threshold voltage is reduced apparently with the increase of NH3/SiH4 gas flow rate ratio.     

Determination of Optical Constant and Thickness for Thin Film by Using Improved FTM

A new method to determine the optical constant and thickness of thin films is proposed. Based on the Fresnel＇s optical expression, the improved flexible tolerance method（FTM） is employed in the case of a digital model of thin film to fit the curve of measured reflectance spectrum. The simulation results show a satisfactory correlation of the optical constant with the thickness of the target film. By taking the influence of nonlinear condition into account as well as more direct and indirect limitation, the precision and value-searching efficiency have been improved. Furthermore, the problem of dimension degradation, which exists in “Downhill Simplex”, has been successfully avoided. No initial input is needed for the procedure of optimization to achieve optical solution, which makes the whole processing of value calculation much more convenient and efficient.     

Effects of the ZnO buffer layer and Al proportion on AZO film properties

To evaluate the influence of the ZnO buffer layer and Al proportion on the properties of ZnO: Al (AZO)/ZnO bi-layer films, a series of AZO/ZnO films are deposited on the quartz substrates by electron beam evaporation. The X-ray diffraction measurement shows that the crystal quality of the films is improved with the increase of the film thickness. The electrical properties of the films are investigated. The carrier concentration and Hall mobility both increase with the increase of buffer layer thickness. However, the resistivity reaches the lowest at about 50 nm-thick buffer layer. The lowest resistivity and the maximum Hall mobility are both obtained at 1 wt% Al concentration. But the optical transmittance of all the films is greater than 80% regardless of the buffer layer thickness with Al concentration lower than 5 wt% in the visible region.     

Ga2O3缓冲层厚度对柔性衬底沉积Cu/ITO薄膜性能的影响

Cu and Cu/ITO films were prepared on polyethylene terephthalate （PET） substrates with a Ga2O3 buffer layer using radio frequency （RF） and direct current （DC） magnetron sputtering. The effect of Cu layer thickness on the optical and electrical properties of the Cu film deposited on a PET substrate with a Ga2O3 buffer layer was studied, and an appropriate Cu layer thickness of 4.2 nm was obtained. Changes in the optoelectrical properties of Cu（4.2 nm）/ITO（30 nm） films were investigated with respect to the Ga2O3 buffer layer thickness. The optical and electrical properties of the Cu/ITO films were significantly influenced by the thickness of the Ga2O3 buffer layer. A maximum transmission of 86%, sheet resistance of 45 Ω/□ and figure of merit of 3.96 × 10^-3 Ω^ -1 were achieved for Cu（4.2 nm）/ITO（30 nm） films with a Ga2O3 layer thickness of 15 nm.     

The effect of film thickness and doping content of SnO2:F thin films prepared by ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin (II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO₂:F thin films were deposited at a 350 ℃ pending time (5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO₂:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9 (Ω·cm^-1) for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO₂:F thin films deposited by ultrasonic spray was reported.     

Transmission spectra of coated phase shifted long-period fiber gratings

The transmission spectrum of the coated phase-shifted long-pcriod fiber gratings （LPFCrs） with single and multiple phase shifts is analyzed by the coupled-mode theory and the transfer matrix method, and the influences of the film parameters on the spectral characteristics are also studied. It is shown that these parameters will affect the LPFG filtering characteristics. The loss peak of Wansmission spectrum decreases with the increase of film thickness, and the peak position shifts with the film refractive index. Compared with the non-coated phase-shifted LPFG, the coated one has the similar desirable filtering characteristics, and it has a flexible ability to adjust the transmission properties.     

Preparation and Properties of C—axis Oriented PT／PEK—c Films

The preparation of PT/PEK-c films is reported as well as their dielectric and optical properties.The c-axis orientation ratio of the films is 68%.Dielectric constant and loss factor at 10kHz is about 4.023 F/m and 0.003, respectively.The refractive indices of the films,ne and no, are 1.6573 and 1.6278 at 0.63μm wavelength, respectively.The optical band-gap of the film with a thickness of 2.33μm is found to be 3.06eV.     

Influences of laser energy density and annealing on structure properties of AIN films prepared by pulsed laser deposition

Aluminum nitride （AlN） films with h〈100〉 crystalline orientation are fabricated on p-Si （100） substrates at room tempera- ture by pulsed laser deposition. The effects of laser energy density and annealing on the quality of the films are studied by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The crystalline quality of AlN films is improved considerably by increasing the laser energy density while there is increased number of farraginous particles on the surface. The annealing treatment at 600~C produces a recrystallization process in the film, characterized by the improvement of the original crystallinity, the appearance of new crystalline orientations, and the increase of the crystallites. The surface becomes rougher due to the increase of the grain size during annealing.     

Optimization of a fiber grating film sensor based on dual peak resonance

Based on the dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity Sn and the thin film optical parameters （the film thickness h3 and the refractive index n3） and the fiber grating parameters （the grating period A and the core index modulation σ）. By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors.     

Effects of Annealing Temperature on Properties of ZnO Thin Films Grown by Pulsed Laser Deposition

ZnO thin films are deposited on n-Si（111） substrates by pulsed laser deposition（PLD） system. Then the samples are annealed at different temperatures in air ambient and their properties are investigated particularly as a function of annealing temperature. The microstructure, morphology and optical properties of the as-grown ZnO films are studied by X-ray diffraetion（XRD）. atomic force mieroseope（AFM）, Fourier transform infrared spectroscopy（FTIR） and photoluminescence（PL） spectra. The results show that the as- grown ZnO films have a hexagonal wurtzite structure with a preferred c-axis orientation. Moreover, the diameters of the ZnO crystallites become larger and the crystal quality of the ZnO fihns is improved with the increase of annealing temperature.     

Effect of deposition conditions on the physical properties of Sn_xS_y thin films prepared by the spray pyrolysis technique

Tin sulfide thin films（Sn_xS_y） with an atomic ratio of y/x = 0.5 have been deposited on a glass substrate by spray pyrolysis.The effects of deposition parameters,such as spray solution rate（R）,substrate temperature （T_s） and film thickness（t）,on the structural,optical,thermo-electrical and photoconductivity related properties of the films have been studied.The precursor solution was prepared by dissolving tin chloride（SnCl₄,5H₂O） and thiourea in propanol,and Sn_xS_y thin film was prepared with a mole ratio of y/x = 0.5.The prepared films were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and UV-vis spectroscopy. It is indicated that the XRD patterns of Sn_xS_y films have amorphous and polycrystalline structures and the size of the grains has been changed from 7 to 16 nm.The optical gap of Sn_xS_y thin films is determined to be about 2.41 to 3.08 eV by a plot of the variation of（αhv）² versus hv related to the change of deposition conditions.The thermoelectric and photo-conductivity measurement results for the films show that these properties are depend considerably on the deposition parameters.     

（AlxGa1—x）yIn1—yP Films an Its Optical Constants on the Surface

The optical parameters for three samples of intrinsic,doped Si and doped Mg（AlxGa1-x)yIn1-yP prepared by the MOCVD on GaAs substrate were measured by using ellipsometry and were calculated by the two-layer absorption film model.The results obtained were discussed.The grown rates and thickness of oxidic layer on the intrinsic（AlxGa1-x)yIn1-yP surface exposed in the atmosphere were studied.Alinear dependence of oxidic layer thickness on the time was obtained.     

Surface-type humidity sensor based on cellulose-PEPC for telemetry systems

In this study, Au/Cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole (PEPC) blend thin films. Blend of 2 wt.% of each cellulose and PEPC in benzol were used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices were observed with the increase of relative humidity in the range of 0−95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing of the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increase of relative humidity, the oscillator’s frequencies were also increased in the range of 4.2−12.0 kHz for 65 μm thick film sample and 4.1−9.0 kHz for 88 μm thick film sample and for 210 μm sample, the oscillator frequency changed in the range of 4.2−9.0 kHz. Effects of film thickness on the oscillator’s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.     

An optical fiber hydrogen sensor with Pd/Ag film

A20 nanometer palladium-silver （Pd/Ag） ultra-thin film was used for hydrogen gas sensing. The atomic ratio of Pd： Ag was 3：1, the thin film was evaporated on the optical glass, the Pd/Ag alloy could increase the life and provide the stability of the sensing film. The artificial neutral network was used for processing the data collected from the optical fiber bundle hydrogen sensor, which could enhance the measuring accuracy, at the same time, the intrinsic and extrinsic influences were eliminated mainly. Experimental results and numerical simulation show the training method available, a linear precision of 0. 1% for the optical hydrogen sensor is achieved.     

A Model of Magneto-mechano-optical Transfer in Fibre-optic Magnetic Sensors with Magnetostrictive Films

Fibre-optic magnetic sensors with magnetostrictive films are used as all-fibre Mach-Zehnder interferometer to detect the optical phase shift, which is caused by the magnetostriction-induced strains transferred from the magnetostrictive film to the fibre. A theoretical model based on the plane strain approximation and uniform axial strain is developed to determine the magneto-mechano-optical transfer relations in this kind of sensors. The expression for the model is presented as well as relation of the phase shift in the fibre to the magnetic and elastic properties of the magnetostrictive film coated on the fibre. And from the model, the thickness of the film has significant influence on the phase shift.