Papers by Keyword: RF Magnetron Sputtering

Abstract: To meet the requirements of second generation photovoltaics, spin coating and RF magnetron sputtering techniques have been utilized to fabricate zinc sulfide thin films for buffer layer optimization. During fabrication process, substrate temperatures for spin coating and RF magnetron sputtering processes are kept at room temperature and at 200 oC, respectively. Thin films are annealed at 500oC for 1 hour in an inert environment to acquire crystallinity and uniform surface morphology. XRD analysis reveals that thin films fabricated by spin coating and RF magnetron sputtering exhibit wurtzite and zinc blende crystal structures, respectively. SEM shows that the surface morphology of thin films fabricated by both techniques is uniform and homogeneous without voids and cracks. EDS results indicate that thin films fabricated via spin coating have equal stoichiometric ratio of zinc to sulfur (1:1). Whereas, an unequal stoichiometric ratio of zinc to sulfur is detected in RF magnetron sputtered thin films. According to optical studies, spin coated zinc sulfide thin films have 67% transmission with an energy band gap of 3.62 eV. While, RF magnetron sputtered thin films have 76% transmission with a wide energy band gap of 3.70 eV. Electrical properties depict that thin films fabricated by RF magnetron sputtering have higher carrier concentration, lower resistivity and higher conductivity than spin coated thin films. In comparison, RF magnetron sputtered zinc sulfide thin films exhibit best structural and optoelectronic properties for buffer layer in second generation solar cells.

Abstract: Transparent conducting oxides (TCO) are semiconducting materials that are electrically conductive as well as optically transparent thus making them suitable for application in photovoltaics, transparent heat transfer windows, electrochromic windows, flexible display, and transparent electronics. One of the methods to enhance the conductivity of metal oxides is doping, however, it can adversely affect the optical transparency of metal oxide. Aluminum (Al) doped zinc (Zn) oxide (AZO) is an important TCO material whose optoelectronic properties heavily rely on the Al doping level. There are various methods to develop AZO thin films. However, since Al and Zn are high vapor pressure materials, and their precise content control isn’t that easy, that’s why we dedicated this study to devise a facile method of Al doping into the ZnO structure. We report a twostep synthesis route to develop AZO thin films over glass substrates. Sub stoichiometric zinc oxide (ZnOx) thin films were sputter deposited over glass employing RF magnetron sputtering at 70W and 9 x 10-3 Torr Ar pressure. To mitigate Zn losses during annealing at 450 °C, the films were first oxidized up to 200 °C in air so as to convert ZnOx into stoichiometric ZnO. To incorporate Al into the ZnO structure, Al was spin coated on top of ZnO from its stabilized sol of 0.07 molar aluminum nitrate nonahydrate in ethanol. The samples were subsequently annealed at 450 °C for 2h in air with a controlled heating ramp of 3 °C/min. The film morphology, microstructure, electronic, and optical characteristics were explored employing scanning electron microscopy, energy dispersive x-ray spectroscopy, Hall effect measurements, and UV-Vis-NIR spectrophotometry, respectively. We found that both the Al and oxygen (O) content affect the optoelectronic behavior of AZO. Even without Al doping, O deficient samples were found to be sufficiently conductive, however, the ZnOx is less transparent relative to O rich stoichiometric ZnO. Furthermore, if ZnOx is annealed at higher temperatures, it causes Zn losses, since Zn is a relatively high vapor pressure material. It degrades the film morphology as well. Once we have ZnO we can confidently treat it at 450 °C to allow Al diffusion into the interiors of the ZnO film. We found that AZO produced via this method is sufficiently conductive as well as transparent.

Abstract: The characteristics of sputtered amorphous diamond-like carbon-containing copper (DLC: Cu films) films deposited on Si (100) substrates and Si (111) in argon gas-filled chamber using carbon target under different substrates deposition time, and RF power. The samples were deposited by RF magnetron sputtering and analyzed using Raman spectroscopy and X-ray reflectivity (XRR) methods. Different parameters of depositions were used to study the structure, thickness, roughness, and density of the samples. The Cu preliminary layer act as a catalyst to growth the DLC thin-film analyzed using XRR analysis to measure thickness, roughness, and density of the thin films. The film structures of the samples were analyzed using Raman spectroscopy with a 532nm laser source. Gaussian peak shapes were used in Raman spectrum fitting to analyzed to measure the D band and G band for both samples. The Films thickness, roughness, and mass density were studied by XRR techniques using XRD to acquire the multilayer structure of thin films grown by magnetron sputtering.

Abstract: Titanium dioxide thin films were deposited by radio frequency sputtering on glass substrates at different substrate temperatures. Hence, we first optimized the preparation conditions and parameters which offer better control and reproducibility of film fabrication. Then, we investigate the structural, morphological and optical properties of the prepared titanium dioxide thin films. To do so, we used several characterization techniques: X-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy and ultraviolet-visible spectroscopy. Interesting results were obtained, e.g. X-ray diffraction analysis shows that the films crystallize only in the anatase tetragonal structure with a preferential orientation along the (101) plane. The intensity of the (101) diffraction peak and the crystallite size are found to increase with increasing substrate temperature, indicating a crystallinity improvement of the films. Raman peaks observed around 144, 197, 399, 515 and 639 cm⁻¹ confirm that all samples possess anatase phase and the crystallinity is enhanced with increasing substrate temperatures. The analysis of scanning electron microscopy and atomic force microscopy images demonstrates that increasing the substrate temperature significantly affects the morphology, grain size and surface roughness of TiO₂ films. The ultraviolet-visible spectroscopy analysis put into evidence that the film deposited at RT is highly transparent in the visible region with average transmittance greater than 84%. Higher substrate temperatures result in a slight decrease of transmittance. Moreover, the direct optical band gap decreases while the refractive index increases with increasing the substrate temperature. Thus, the obtained results reveal that ultraviolet-visible can be considered as a potential material for optical and photovoltaic applications.

Abstract: Zinc Oxide (ZnO) thin films were deposited on glass substrate by radio frequency (RF)reactive magnetron sputtering technique at variable Oxygen flow rates while Argon flow rates waskept constant. The effect of oxygen flow rate on structural, electrical, optical properties of nanostructured ZnO thin films were investigated by X-ray diffractometer, scanning eletron microscopy(SEM), Hall effect measurements and UV-Visible spectrophotometer. X-ray diffraction (XRD) datareveals films are polycrystalline hexagonal structure with (002) peak as a preferred orientation andcrystallite size was found to be in range12 nm-16 nm.The electrical resistivity of films decreasesfrom 10^-1 Ω-cm to 10^-2 Ω-cm. All deposited ZnO thin films shows high transmittance above 95% inthe visible range 360 nm-800 nm. The optical band gap and refractive indices have been calculatedusing UV-Vis transmission spectra. Oxygen gas flow rates found to have large impact onoptoelectronic properties of ZnO films.

Abstract: A series of ZrN-Ag nano-composite films were deposited using the RF magnetron sputtering system. The microstructure, mechanical properties and tribological performances were investigated. The results showed that ZrN-Ag films were composed of face-centered cubic (fcc)-ZrN and face-centered cubic (fcc)-Ag. With the increase of Ag content, the hardness of ZrN-Ag composite film increased rapidly and then decreased rapidly. The maximum hardness value was 22.8 GPa at 6.1at.% Ag. At room temperature, the coefficient of friction (Cof.) of ZrN-Ag films were lower than the ZrN film. During 25-500°C, the Cof. of ZrN-Ag films at 29.16 at.% Ag were lower than ZrN film, while the wear rate were higher than the ZrN film. In summary, the addition of Ag improved the hardness, and decreased the Cof. of the ZrN-Ag during 25-500°C.

Abstract: A series of oxygen-deficient tin oxide thin films were deposited by radio frequency magnetron sputtering a sintered tin oxide ceramic target under pure argon atmosphere at different sputtering powers (80-160 w) under the based pressure of no more than 2.0×10^-4 Pa, sputtering pressure of 2.0 Pa and deposition time of 20 min. It was revealed that all the as-deposited films were oxygen-deficient tin oxide films, and the main defect in films was oxygen vacancy (V_O), whose concentration gradually decreased with the increase of sputtering power. The films prepared at a power of no more than 120 w were amorphous, and as the sputtering power increased to 140 and 160 w, the deposited thin films exhibited polycrystalline characteristics with (110), (101) and (211) diffraction peaks of tin oxide. The grain size, deposition rate as well as thickness of the obtained films rose up with increasing sputtering power. In addition, as the sputtering power raised, the electrical resistivity of the films increased, due to the electron conducting mechanism controlled by V_O in the samples.

Abstract: The aim of this study was to evaluate surface characteristics and biological properties of the dentin derived hydroxyapatite (DDHA) coating on titanium substrate. DDHA was derived from extracted human teeth with calcination method at 850°C. The commercially pure titanium was used as a metallic substrate and a RF magnetron sputtering method was used as a coating method. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX) were performed to investigate the morphology and composition of coating surface. Atomic Forced Microscopy (AFM) and surface profiler were used to assess the surface morphology and roughness. Corrosion tests were performed in phosphate buffered saline at a 36.5±1°C in order to determine the corrosion behavior of the uncoated and coated surface samples. The biocompatibility of DDHA coating surface samples with murine osteoblastic cells was assessed by SEM. As a results, thin coating layer was observed on SEM images and uniformly cover the surfaces without change of titanium substrate. The EDX analysis of this coating surface indicated the presence of Ca, P elements. The mean surface roughness of cp-Ti and DDHA coating samples was 0.27μm, 1.7μm, respectively. The corrosion test indicated the stable passive film on coating samples. SEM observations of murine osteoblastic cells on coating surface showed that cells have proliferated and developed a network of dense interconnections. These results suggest that DDHA coating with RF magnetron sputtering method has good surface characteristics and biocompatibility.

Abstract: The thermal insulation function of tungsten-doped vanadium dioxide (V₂O₅) thin films deposited on non-alkali glass substrate using RF magnetron sputtering was analyzed in this study. Grinded hot-dry V₂O₅ and tungsten powders, mixed in weight ratio of 98.1:1.9 or 97:3, were pressed at 800 psi for 10 min. These compounds were sintered at 550 or 600 °C for 8 hours, in oxygen gas environments (10 sccm and 0 sccm), to several W-doped V₂O₅ targets. The surface morphologies of these targets were analyzed by a SEM, and the crystal structure was characterized by a XRD. The experimental studies with reference to the thermal insulation property of V₂O₅ were conducted under various duration of deposition, substrate temperatures, rf powers and duration of annealing time. The influence of these factors was investigated using the Taguchi method, an orthogonal array L₈. The results show that the targets contain a more homogenous structure and a larger grain size with higher oxygen gas flow rate. With a deposition-parameter combination of 60 min (duration of deposition), 300°C (substrate temperature), 150 W (rf power) and 60 min (duration of annealing time), the optimal thermal insulation temperature, 19.3°C, was observed.

Abstract: Barium strontium titanate (BST) thin films with excellent dielectric properties are deposited by on-axis RF magnetron sputtering system. The effects of composition of the target and oxygen partial pressure on the microstructure of BST thin film have been investigated. The dielectric properties of the thin films are investigated. The results show that composition of BST thin film deposited with pure argon ambient by the target with 30atm% excess of Ba and Sr is stoichiometric. Perovskite phase can be observed in the thin film annealed in oxygen at 750 °C for 30 min. A metal-insulator-metal (MIM) capacitor is fabricated by microfabrication technique. The capacitance value at 2 GHz is 0.417 pF and 1.42 pF for 50 nm and 90 nm BST thin film respectively, and the leakage current density is 6×10^-6 A/cm² and 5.35×10^-8 A/cm² respectively.