Effect of RF power on the structural and optical properties of ZnS thin films prepared by RF-sputtering

Zinc sulphide(ZnS) thin films have grown on glass and Si substrates by reactive cathodic radio frequency(RF) sputtering. The RF power was varied in the range of 100 to 250 W, while the deposition time is set at75 min. The optical, structural, and morphological properties of these thin films have been studied. The optical properties(mainly thickness, refractive index,absorption coefficient, and optical band gap) were investigated by optical transmittance measurements in the wavelength range of ultraviolet-visible-near infrared spectroscopy and spectroscopy infrared with Fourier transform. Fourier(FT-IR) and XRD analysis indicated that all sputtering ZnS films had a single-phase with a preferred orientation along the(111) plane of the zinc sphalerite phase(ZB). The crystallite size ranged from 11.5 to 48.5 nm with RF power getting a maximum of 200 W. UV-visible measurements exhibited that the ZnS film had more than 80% transmission in the visible wavelength region. In addition, it has been observed that the band gap energy of ZnS films is decreased slightly from 3.52 to 3.29 eV, and as the RF power is increased, the film thickness increases with the speed of deposit growth. Scanning electron microscopy observations revealed the types of smooth-surfaced films. The measurements(FT-IR) revealed at wave number1118 and 465.02 cmabsorption bands corresponding to the symmetrical and asymmetric vibration of the Zn-S stretching mode. X-ray reflectometry measurements of ZnS films have shown that the density of the films is(3.9 g/cm~3) close to that of solid ZnS.

Effects of thermal annealing on the properties of N-implanted ZnS films

N-ion-implantation to a fluence of 1 × 1015 ions/cm^2 was performed on ZnS thin films deposited on glass substrates by using the vacuum evaporation method. The films were annealed in flowing nitrogen at 400 ℃-500 ℃ after N-ion-implantation to repair the ion-beam-induced structural destruction and electrically activate the dopants. Effects of ion-implantation and post-thermal annealing on ZnS films were investigated by X-ray diffraction （XRD）, photoluminescence （PL）, optical transmittance, and electrical measurements. Results showed that the diffraction peaks and PL intensities were decreased by N-ion-implantation, but fully recovered by further annealing at 500 ℃. In this experiment, all films exhibited high resistivity due to the partial dopant activation under 500 ℃.

Magnetic Properties of NiCuZn Ferrite Thin Films Prepared by the Sol-gel Method

Ni0.4Cu0.2Zn0.4Fe2O4 thin films were fabricated on Si substrates by using the sol-gel method and rapid thermal annealing （RTA）, and their magnetic properties and crystalline structures were investigated. The samples calcined at and above 600 ℃ have a single-phase spinel structure and the average grain size of the sample calcined at 600 ℃ is about 20 nm. The initial permeability μi, saturation magnetization M and coercivity H of the samples increase with the increasing calcination temperature. The sample calcined at 600 ℃ exhibits an excellent soft magnetic performance, which has μi=33.97 （10 MHz）, Hc=15.62 Oe and Ms=228.877 emu/cm^3. Low-temperature annealing can enhance the magnetic properties of the samples. The work shows that using the sol-gel method in conjunction with RTA is a promising way to fabricate integrated thin-film devices.

Effect of Pre-heating Temperature on Structural and Optical Properties of Sol-gel Derived Zn_(0.8)Cd_(0.2)O Thin Films

Zn_（0.8）Cd_（0.2）O thin films prepared using the spin-coating method were investigated. X-ray diffraction, scanning electron microscopy, and UV-Vis spectrophotometry were employed to illustrate the effects of the pre-heating temperature on the crystalline structure, surface morphology and transmission spectra of Zn_（0.8）Cd_（0.2）O thin films. When the thin films were pre-heated at 150 ℃, polycrystalline Zn O thin films were obtained. When the thin films were pre-heated at temperatures of 200 ℃ or higher, preferential growth of Zn O nanocrystals along the c-axis was observed. Transmission spectra showed that thin films with high transmission in the visible light range were prepared and effective bandgap energies of these thin films decreased from 3.19 e V to 3.08 e V when the pre-heating temperature increased from 150 ℃ to 300 ℃.

Pulsed Laser Deposition ZnS Buffer Layers for CIGS Solar Cells

Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suitable alternative to chemical bath deposited （CBD） CdS as a buffer layer in Cu（In,Ga）Se2 （CIGS） solar cells. X-ray diffraction studies indicate the films are polycrystalline with zinc-blende structure and they exhibit preferential orientation along the cubic phase β-ZnS （111） direction, which conflicts with the conclusion of wurtzite structure by Murali that the ZnS films deposited by pulse plating technique was polycrystalline with wurtzite structure. The Raman spectra of grown films show Al mode at approximately 350 cm^-1, generally observed in the cubic phase β-ZnS compounds. The planar and the cross-sectional morphology were observed by scanning electron microscopic. The dense, smooth, uniform grains are formed on the quartz glass substrates through PLD technique. The grain size of ZnS deposited by PLD is much smaller than that of CdS by conventional CBD method, which is analyzed as the main reason of detrimental cell performance. The composition of the ZnS films was also measured by X-ray fluorescence. The typical ZnS films obtained in this work are near stoichiometric and only a small amount of S-rich. The energy band gaps at different temperatures were obtained by absorption spectroscopy measurement, which increases from 3.2 eV to 3.7 eV with the increasing of the deposition temperature. ZnS has a wider energy band gap than CdS （2.4 eV）, which can enhance the blue response of the photovoltaic cells. These results show the high-quality of these substitute buffer layer materials are prepared through an all-dry technology, which can be used in the manufacture of CIGS thin film solar cells.