Papers by Keyword: Thin Film

Abstract: Due to the inertness of the intrinsic (nondoped) amorphous SiC (i-aSiC) material to the chemical impact, for making it porous by the electrochemical etching method, one must use the electrolyte solution with an appropriate composition. For this purpose we have found that besides the use of solutions containing surface activation agent (Triton X-100 for example), one can use also solutions containing oxidation agent. In this report we present the results obtained with electrolyte solution in which H₂O₂ plays the role of oxidation agent. Results showed that with appropriate ratio of components in the HF/H₂O/H₂O₂ solution, we can manufacture a porous layer in the i-aSiC thin film with the porosity similar to the porosity of the porous layer obtained by etching in the HF/H₂O/Triton X-100 solution with optimal composition. Thin film of i-aSiC material with porous surface layer can be used in different types of sensors.

Abstract: Silver telluride (Ag2Te), I-VI semiconductor compound with potential applications in various advanced fields. Ag2Te nano films of thickness between 16 nm and 145 nm prepared by thermal evaporation technique at high vacuum better than 2x105 mbar. These films are found to exhibit polycrystalline nature with monoclinic structure from their XRD studies. The average particle size of these films are found to be around 24 nm using the Debye-Scherrer’s formula From AFM measurements, the average particle size is around 24 nm. The emission spectra of these films were recorded and analysed to determine its optical band gap. Optical band gap of Ag2Te varies from 1.6 eV to 1.8 eV with respect to their corresponding thicknesses of films.

Abstract: This study investigates the preparation of the three main layers of a CdS/CdTe thin film solar cell using a single vacuum system. A Close Space Sublimation System was constructed to deposit CdS, CdTe and CdCl2 solar cell layers. Two hot plates were used to heat the source and the substrate. Three fused silica melting dishes were used as containers for the sources. The properties of the deposited CdS and CdTe films were determined via Atomic force microscopy, scanning electron microscopy, X-ray diffraction and optical transmission spectroscopy. An J-V characterization of the fabricated CdS/CdTe solar cells was performed under solar radiation. The short-circuit current density, Jsc, the open-circuit voltage, Voc, fill factor, FF and conversion efficiency, η, were measured and yielded values of 27 mA/cm2, 0.619 V, 58% and 9.8%, respectively.

Abstract: The experiments focused on thin film buckling under impact load had been completed. The axial impact experiments were done to different films on the PMMA substrate with the drop hammer device, the buckling images of the film surface were recorded after impact, and the problem of stress release was studied. It was found that buckle’s initiation and propagation were influenced by the materials of thin films and the impact times, and meanwhile buckle’s local distribution phenomenon was also found.

Abstract: The Cu2ZnSnSe4 (CZTSe) thin films were prepared by co-electroplating Cu-Zn-Sn precursors followed by selenization at different substrate temperatures. The effect of substrate temperatures on the morphologies and structures of CZTSe films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum respectively. The results revealed that the impurity phases in CZTSe thin films such as CuSe and SnSe disappeared when the substrate temperatures were increased. The surface morphologies of CZTSe thin films were also strongly dependent on the substrate temperature treatment in the selenization process though the selenium temperature was kept at 340°C.

Abstract: In this research, the effect of precursor concentration of CuI thin film deposited by spin coating method was studied. The wide band gap p-type semiconductor CuI thin film was prepared by mixing the CuI powder with 50 ml of acetonitrile as a solvent. The CuI concentration varies from 0.05M to 0.5M. The speed for spin coating is 1000 rpm for 60 seconds. After the deposition the CuI thin films were annealed at 150°C. The result shows the CuI thin film properties strongly depends on its precursor concentration. Thickness between 33.65 nm - 441.25 nm was obtained as the concentration increased. The increment of thickness affected the electrical property with resistivity of about 10^-6 Ω.cm and 10¹ Ω.cm was observed for all the CuI thin films. For optical properties, the transmittance decreased with high concentration as high amount of CuI particle were observed in the thin films. From the transmittance, the absorption coefficient of 10^-6 m^-1 and optical band gap of 3.10 and 3.50 eV for all the films were observed using Tauc’s plot.

Abstract: Nanocrystalline PbS thin films were prepared using chemical bath deposition method on glass substrates, together with lead acetate as a source of lead ions (Pb²⁺) and thiourea as a source of sulfide ions (S^2-) with different molar concentrations. The structural properties of thin films were studied using X-ray diffraction.The patterns showed a polycrystalline structure, and the preferred orientation changed along (111) and (200) planes .The grain size of the thin films varied from 27 to 41 nm. The crystallites were under strain, which varied between 0.054 and 0.3. Scanning electron microscope images showed that all the films have uniform surface morphology over the entire glass substrate and that the films were of good quality.

Abstract: In this study, the design of the mechanism of a recycling system using composite electrochemical and chemical machining for removing the surface layers from silicon wafers of solar cells is studied. The reason for constructing a new engineering technology and developing a clean production approach to perform the removal of surface thin film layers from silicon wafers is to develop a mass production system for recycling defective or discarded silicon wafers of solar cells that can reduce pollution. The goal of the development is to replace the current approach, which uses strong acid and grinding and may cause damage to the physical structure of silicon wafers and cause pollution to the environment, to efficiently meet the requirements of industry for low cost. It can not only perform highly efficient recycling of silicon wafers from discarded solar cells to facilitate the following remelting and crystal pulling process, but can also recycle defective silicon wafers during the fabrication process of solar cells for rework. A small gap width between cathode and workpiece, higher temperature, higher concentration, or higher flow rate of machining fluid corresponds to a higher removal rate for Si3N4 layer and epoxy film. Pulsed direct current can improve the effect of dregs discharge and is advantageous to associate with the fast feed rate of workpiece, but raises the current rating. A higher feed rate of silicon wafers of solar cells combine with enough electric power produces fast machining performance. The electrochemical and chemical machining just needs quite short time to make the Si3N4 layer and epoxy film remove easily and cleanly. An effective and low-cost recycle process for silicon wafers of solar cells is presented.

Abstract: TiN thin films were deposited by Arc Ion Plating(AIP) with or without Magnetic Filter(AIP or MFAIP) on silicon(Si) and high-speed steel(HSS) substrates,respectively.Scanning Electron Microscope(SEM),X-ray Diffraction(XRD),nanoindentation and microscratch tests were applied for microstructure and property investigation.SEM data showed that the AIP films are plagued with macro-particles(MPs),while the MFAIP films have no or less MPs.XRD showed that the MFAIP films have more obvious preferred orientation at (111) than the AIP films.Scratch Crack Propagation Resistance(CPRs) was introduced to evaluate the film adhesion properties in a scratch test.MFAIP films had higher adhesion.AIP films were susceptible to failure as the CPRs was lower.The MFAIP films had higher hardness than the AIP ones, due to the reason of less MPs in MFAIP films and more obvious preferred orientation.It was proposed that the MPs were effectively removed with the magnetic filter, so the properties of the MFAIP films were greatly improved.

Abstract: The novel lithium enriched lithium tantalate (LiTaO₃) targets were papered by employing the sol-gel process and the high temperature sintered process. The sol of LiTaO₃ was firstly prepared through reacting lithium ethoxide with tantalum ethoxide. The LiTaO₃ powder was fabricated by presintered LiTaO₃ dry gel 4 hour, at 800°C. The 11cm13cm1cm lithium enriched LiTaO₃ target samples were prepared by sintered the pressed LiTaO₃ powder billet 4 hour in the 850°C muffle furnace. The density of the 5% overdose lithium enriched LiTaO₃ target is measured 5.96g/cm³. The XRD measured results show that the ion beam enhanced deposited (IBED) thin film samples using the prepared 5% overdose lithium enriched LiTaO₃ target have the polycrystal structure of LiTaO₃, but there has remanent Ta₂O₅ existed in the IBED thin film samples. The main reason for the remanent Ta₂O₅ growth was due to the stoichiometric proportion mismatch between Li and Ta in the IBED thin film samples during the high temperature annealed process, which caused the lithium oxide evaporation loss from the IBED thin film samples and made the proportion of Ta₂O₅ increase. After multipule repeated target prepared experiments, the 8.76% overdose lithium enriched LiTaO₃ target is suitable for fabricating the 550°C annealed IBED LiTaO₃ thin film. After the repeated process experiments, the suitable deposited process parameters of the IBED-C600M instrument for the 8.76% overdose lithium enriched LiTaO₃ target were obtained. The SEM micrographs of the 550°C annealed IBED LiTaO₃ thin films prepared by the 8.76% overdose lithium enriched LiTaO₃ target reveal the prepared thin films are uniform, smooth and crack-free on the surface, and the perfect adhesion between the thin film and the substrate. The successfully fabricated LiTaO₃ thin film samples verify the prepared processes of novel LiTaO₃ sputtering target are effective.