Papers by Keyword: Thin Film

Abstract: Nanostructured Pt thin films were electrodeposited in the presence of varying amounts of xanhtine. The electrodeposited Pt films exhibit different catalytic efficiency for methanol electro-oxidation. The anodic current of methanol decreases linearly with the increase of xanthine during the electrodeposition. The effect of xanthine on the catalytic efficiency of Pt films was studied by cyclic votlammetry (CV) and differential pulse voltammetry (DPV). The results of CV and DPV reveal the formation of a 2:1 complex between Pt(IV) and xanthine. The conditional stability constant of the complexes was determined to be 3.8×10⁶.

Abstract: A low-cost non-vacuum process for fabrication of Cu2ZnSnSe4 (CZTSe) films by solvent-free mechanochemical method and spin-coating process is described. First, highly monodisperse Cu, Zn, Sn oxides nanoparticles are synthesized via a facile, solvent-free route. Second, the oxide particulate precursors are deposited in a thin layer by spin-coating technique. Finally, the dry layers are sintered into CZTSe thin films selenization. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), it is found that near stoichiometric CZTSe films with a micron-sized grains are obtained in our work.

Abstract: Aluminium doped ZnO (ZnO:Al) films were deposited on polymer substrates by RF magnetron sputtering. The effects of deposition temperatures on structure and properties of films were investigated by X-ray diffractometery, Scanning electronic microscopy, UV-visible spectrophotometer, as well as Four-point Probes System. The results revealed that moderate deposition temperature was helpful to improve the crystal quality and optoelectronic properties of ZnO:Al films. The lowest resistivity of 9.5×10^-3Ω•cm and the average transmittance of 76% in the visible region was obtained for the film deposited from ZnO:2wt% Al₂O₃ target at 75°C.

Abstract: Two-dimensional modeling and the computational fluid dynamics simulation are performed to investigate the deposition rate and the uniformity of the thin film under different power in PECVD reaction chamber using 13.56 MHz frequency. The results of the simulation show that as the power increased, the deposition rate of the thin film first increased gradually and then saturated, but the changes of power have little effect on uniformity.

Abstract: _{Subscript text}Reactive ion etching of barium strontium titanate (BST) thin films using an SF₆/Ar plasma has been studied. BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism, and chemical reactions had occurred between the F plasma and the Ba, Sr and Ti metal species. Fluorides of these metals were formed and some remained on the surface during the etching process. Ti can be removed completely by chemical reaction because the TiF₄ by-product is volatile. Minor quantities of Ti-F could still be detected by narrow scan X-ray photoelectron spectra, which was thought to be present in metal-oxy-fluoride(Metal-O-F). These species were investigated from O_1s spectra, and a fluoride-rich surface was formed during etching because the high boiling point BaF₂ and SrF₂ residues are hard to remove. The etching rate was limited to 14.28nm/min. A 1-minute Ar/10 plasma physical sputtering was carried out for every 4 minutes of surface etching, which effectively removed remaining surface residue. Sequential chemical reaction and sputtered etching is an effective etching method for BST films.

Abstract: In this study, the physical, electrical, and structural parameter on radio frequency (RF) sputtered molybdenum thin film is investigated as a function of two deposition parameters: rf power, and argon (Ar) pressure. Films are sputtered onto the substrates nominally held in room temperature in a RF sputtering system at partial argon (Ar) pressure. A number of 10 films are deposited at 8 sccm of Ar pressure while varying the rf power from 90 to 360 watt. Besides, another set of 7 films are deposited at 240 watt RF power while varying the Ar pressure from 8 to 32 watts. All the films are characterized using FESEM, AFM, XRD, and four points probe. The analysis results substantiate that, to fabricate a low resistive thin layer of molybdenum (Mo) both sputtering power, and deposition time Ar pressure plays significant rules. It is found that, with the increase of the RF power (90 to 280 watt) the deposition rate increase from 1.2 A⁰/sec to 4.4 A⁰/sec. But at a RF power higher than 280 watt the deposition rate saturated and it does not increase as linear as before. Also resistivity continuously decreases as the RF power increases from 90 watt up to 270 watt, after that the resistivity remain almost same regardless the RF power increased. Besides, by varying the Ar pressure it is found that with the increase of the Ar pressure the deposition rate increase until 20 sccm (up to 2.4 A⁰/sec). With further increase of the Ar pressure deposition rate start reducing and reached 2.1 A⁰/sec at 32 sccm. Based on the above investigation and analysis optimized film is deposited and further analyzed. The surface roughness is analyzed using AFM characterization tool and found 27.4519 nm. The FESEM and XRD analysis along with the resistivity of the film is used to measure the strain of the deposited film and found a strain of less than 0.01% on the optimized film, which is essential for MEMS/NEMS device fabrication and energy harvesting applications.

Abstract: Optical, surface and structural properties of ZnO thin films fabricated by reactive radio- frequency (rf) magnetron sputtering and sol-gel coating methods are comparatively investigated. The optical properties of films produced by both techniques have very similar characteristics, however; the surface morphology and degree of crystallinity have different behaviors. The nanostructure columnar zinc oxide thin films can be synthesized by sol-gel coating methods which can have numerous applications requiring larger surface area. Also, the process scalability and large-scale manufacturing of these materials are discussed. It indicated that the nanostructure ZnO thin films can be synthesized with sol-gel methods at wafer levels with nano-grains and improved surface properties compared with reactive rf magnetron sputtering deposition.

Abstract: 25% Zinc doped Cadmium Telluride thin films were prepared using Stacked Elemental Layer method. The structural studies were conducted by the X-Ray technique and the results were compared with standard data which confirmed the presence of mixed phases (CdTe, ZnTe and CdZnTe) in the stack annealed at 425°C. Transmittance spectra depicted the effect of Zn on the optical properties of CdTe thin film. The calculated band gaps from the transmittance spectra were lie between 1.42 and 1.51eV. Scanning Electron Microscope images elucidated the influence of Zn on surface morphology and the grain growth for CdTe thin films.

Abstract: Nickel furfuraldehyde thiosemcarbabazone adduct of the type, NiCl₂(L)₂ (L = furfuraldehyde thiosemicarbazone) was synthesized by the reaction between nickel dichloride hexahydrate and furfuraldehyde thiosemicarbazone in 1:2 stoichiometry. The resulting compound was characterised by elemental analysis, IR, ¹H and ¹³ C{¹H} NMR spectral data. It was further used as a single-source precursor for the deposition of nickel sulfide thin films by aerosol assisted chemical vapour deposition (AACVD) technique and the nickel sulfide nanocrystallites by pyrolysis and solvothermal decomposition methods. The thin films obtained were characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX) and atomic force microscopy (AFM). The nanocrystallites obtained were also characterized by XRD, EDAX as well as transmission electron microscopy (TEM). The SEM images of the thin films show formation of different morphologies of nickel sulfide, i.e. nanoball-like, nanowires to flower-like depending on the growth temperature. The mechanism for the variation of the morphology with the growth temperature has been proposed. The XRD of the nanocrystallites obtained matches with the hexagonal phase of nickel sulfide and the TEM images show formation of 10-50 nm spherical nano-crystals.

Abstract: A theoretical analysis of Vacuum Film Deaeration(VFD) based on the characteristics of fluid film on a rotating cone surface is carried out. The motion equation of bubble is derived to find out its relative slip velocity in the flowing film. And the bubbles removal time from the high viscosity liquid is discussed. The thickness model of liquid film on the rotating surface and the residence time of the film flows over the surface are built in this paper. It is found that the thickness and the velocity of the flowing film on the rotating cone surface are the key parameters for VFD; the time of bubble remove mainly includes the growth time and the rest time; the velocity of bubble is slightly lagging behind the main flow; the low angular velocity has little effect on the film thickness; and the time of VFD for flowing film is less than that of static film.