Thin Film Technology

We deposited CdS and ZnS chalcogenides thin films on different substrates by Chemical Bath Deposition Technique. Structural, Surface Morphology and Optical properties of as deposited CdS and ZnS films were investigated by XRD, SEM, FTIR and UV-VIS Spectrophotometer. It is found that, the average grain size of CdS and ZnS in the films is 08 to 130nm and 08 to 113nm. The band gap is also calculated from the equation relating absorption co-efficient to wavelength. The band gap indicates the film is transmitting within the visible range and the band gaps changes because of the grain size of the CdS and ZnS in the films. We also observed that, the change in preparative parameters affects the deposition rate of thin films. From the observation, it is clear that the growth rate increases as the deposition temperature, deposition time, molarities of the solution increases. It is also clear that the growth rate increases as the film thickness and grain sizes increases while band gap decreases.

Well-ordered SAMs using adipic acid were formed on the oxide of iron carbon steel surface by immersion method. This leads to ordered, robust monolayers bound to the surface in a tetradentate manner. Monolayer formation takes place when carbon steel is immersed in an aqueous solution containing 60ppm of Cl– and 100ppm of adipic acid for 5 minutes, and rinsing the physisorbed molecules in distilled water and heating in a hot air oven. The adipic acid monolayers on iron oxide steel carbon can withstand rinsing with water, concentrated acid and base exposure. Additionally, these monolayers are stable over the course of at least one week. The formations of monolayers were confirmed by AFM study and FTIR spectra. The SAMs were tested by polarization and EIS electrochemical analysis. The results of this study show that adipic acid monolayers adsorbed on metal surface can reduce electrochemical activity on the surface, often the first step in corrosion.

Nanocrystalline lead sulphide thin films have been deposited on glass substrates from chemical baths containing lead acetate, sodium hydroxide, ammonia and thiourea at a bath temperature of 90 0C and a pH of about 12. Three different samples were prepared with deposition times of 30, 45 and 60 minutes respectively. The films were characterized using a variety of techniques. X-ray diffraction analyses revealed that all the films were polycrystalline in nature with the diffraction peaks indexed to the face centered cubic structure. The deposition time strongly influenced the preferred orientations of the crystallites as well as structural parameters such as average crystallite size, strain and dislocation density. SEM micrographs of all the films showed a highly compact surface composed of sharp-edged cubic shaped grains of different sizes. The elemental compositions of the films were confirmed by energy dispersive X-ray spectroscopy. The optical band gap of the films decreased from 1.32 eV to 1.10 eV with increasing deposition time.

Semiconducting materials in thin film form are of great interest due to their distinctive physico-chemical properties towards optical and optoelectronic device applications. Zinc oxide (ZnO) is one of the well-known II-VI group wide-band gap semiconductor which shows the wide range of applications such as optical filters, short wavelength emission, transparent conducting, laser diodes and intense luminescence applications etc.,. In the present work the ZnO thin film was fabricated on well cleaned glass substrates by spray pyrolysis technique and the structural, surface and optical properties were investigated by powder X-ray diffraction, scanning electron microscopy and UV-vis spectroscopy at room temperature. Structural parameters such as crystallite size, microstrain and dislocation density were calculated by using Scherrer’s formula. The applicability of the spray deposited ZnO thin film towards window material in solar cell application are presented and discussed in the present work.

Cadmium zinc sulfide (CdZnS) thin film was deposited on transparent conduction Indium tin oxide (ITO) coated glass substrate by a cost effective chemical bath deposition (CBD) method. Commercially purchased ITO coated glass substrate with sheet resistance 8 ?/cm2 was utilized for the deposition of CdZnS thin film under optimized chemical bath conditions. Surface texture of the fabricated CdZnS thin film was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis. The optical absorption and transmittance properties of the fabricated CdZnS thin film was investigated by UV-Vis spectroscopy in the wavelength range of 300 to 1100 nm. The investigated surface and optical properties of the fabricated CdZnS thin film towards optical applications are presented and discussed.

Tin Oxide thin films were deposited by sol gel dip coating method using the acrylamide route. The films were post heated at different temperature in the range of 350-525 ^oC. X-Ray diffraction (XRD) studies indicatyed the formation of tetragonal SnO₂. The Optimum temperature for the formation of the films was 450 ^oC.Microstructural parameters were estimated from the XRD data. XPS studies indicated the peaks corresponding to Sn 3d and 01s. Transmission spectra exhibited interference fringes. Refractive Index was in the range of 2.05-2.18. Optical bandgap value was around 3.68 eV. Three fundamental Raman lines are observed which agree well with that of the bulk material.

Tin doped zinc oxide thin films have been deposited by reactive evaporation, the deposition has been done at various doping levels ranging from 1% to 8%. The optical properties have been characterized using UV-VIS-NIR spectrophotometer, the data for transmittance has been used for further analysis using scout. The transmittance of doped thin films has been found to be > 75% while for those of as prepared samples has been found to be even higher. The bandgap calculations have shown that the band gap for as prepared and doped thin films ranges between 2.95 – 3.95 eV. The electrical characterization has been done mainly at room temperature using a well calibrated four point probe. The sheet resistivity has been found to range from 24.3-26.7 Ohm cm. The coating have been found to be suitable for antireflectance as well as transparent contacting oxide applications.

In this paper we synthesis various thickness of nickel oxide (NiO) nanostructure films deposited on si substrate. by using RF. Reactive magnetron sputtering technique rotating by 5 cycle/min with both Argon and Oxygen mixture gases .argon and oxygen partial pressure was(7.0×10-3torr)and(1.89×10-2torr) respectively. The gas sensing application and electrical properties investigated as a function to the thickness variation the dramatic change in the electrical properties shows strong dependence on the thickness variation. Conductivity, resistivity, gas sensitivity of hydrogen and nitrogen dioxide gases was (95 %) and (90 %) for 50 nm respectively, gas sensitivity for NiO films increasing as film thickness increasing.

Thin film patterned CdS is considered to be as the most promising semiconducting materials among various structures because of its tunable physical properties which leads the material to the recent applications such as solar cells, sensors, hydrogen storage devices, modulators etc. Moreover, in order to form CdS thin films chemical bath deposition techniques is one of the easiest method among various techniques. It is due to the fact that it has many advantages such as simplicity, no requirements for sophisticated instruments, minimum wastage, economical way of large area deposition, no need of handling poisonous gases and possibility of room temperature depositions. With these advantages in mind an attempt has been made to deposit device quality CdS thin films at various temperatures by CBD technique. The thicknesses of the deposited films have been determined by gravimetry. The structural characterization is carried out by X-ray diffraction. The study confirms the polycrystalline nature of films with hexagonal structure. The structural parameters such as grain size, dislocation density, strain and lattice parameters have been evaluated. The composition of various constituents in CdS films have been determined by energy dispersive X-ray analysis. The optical properties like optical transmittance, band gap and refractive index has been studied in detail for the CdS films of various thicknesses.

In this study, tin selenide was prepared at different ratios using tin and selenium pellets in glass tube filled with argon and then heated up to 350°C. The resulting materials were cut into ingots which were used in preparation of thin films by thermal evaporation. The evaporation was done using Edwards auto 306 coating unit. The chamber pressure was maintained at 5.0 x 10-5mbars during the film deposition. Thin films of tin-selenide produced using various ratios were characterized for optical properties and sheet resistance. The optical measurements were done using UV-VIS-NIR spectrophotometer Solid State 3700 DUV in the visible range (380-750nm) and the transmittance spectra data obtained was analyzed using the SCOUT software. The films with ratio of 1:1 showed the highest transmittance of 85% with a band gap energy obtained as 1.40eV. The electrical characterization measurements were carried out using a four point probe at room temperature (25°C) to obtain the sheet resistivity. The resistivity obtained for the films was 20.1?cm.