Key Engineering Materials Vols. 675-676

Abstract: In this work, niobium oxide thin films were deposited on silicon wafer (100) and glass slide substrate by reactive magnetron sputtering. The niobium oxide films were further annealed and effect of post annealing on the crystallinity, microstructure and optical properties was studies. In order to identify the crystalline structure and microstructure, X-ray diffraction (XRD) and scanning electron microscope (SEM) measurement carried out. The optical property was determined by UV-Vis spectrophotometer. It has been observed that with increase in annealing temperature films become microcrystalline films. In particularly, the optical property of niobium oxide thin film also improves with annealing temperature.

Abstract: Indium doped tin oxide (ITO) thin films were deposited on silicon wafer (100) and glass slide by ion assisted electron beam evaporation deposition. After deposition, the ITO thin films were annealed in vacuum (100-300°C) and their structural, optical and electrical properties were systematically investigated. X-ray diffraction,atomic force microscopy, ultraviolet–visible (UV–vis) spectrophotometer and hall-effect measurement were employed to obtain information on the crystallization, transmission and resistivity the films.It was found that the rapid thermal annealing can improve the resistivity of ITO thin films which specializes for the transparent conductive layers.

Abstract: We prepare Lead Telluride (PbTe) thin film by DC magnetron sputtering method. The powder precursors of Pb and Te purity 99.99 % ratio 1:1 were mixed. PbTe Powder was pressed using as sputtering target. DC magnetron sputtering condition, the base pressure is 3.2×10⁻³ Torr, applied the argon gas (purity 99.99%) in vacuum chamber to obtained working pressure at 50×10⁻³ Torr. The sputtering power is 25 W and sputtering time is 30 minutes. Phase identification, morphology and film thickness have been investigated by X−ray diffraction and scanning electron microscope. Electrical resistivity and Seebeck coefficient of the PbTe thin films have been investigated by four probe steady state method. The results demonstrated that the crystal phase of PbTe is face center cubic (FCC) structure. The average PbTe films yielded film thickness is around 460 nm, the average electrical resistivity is 17 Ω m and seebeck coefficient is 8.0×10⁻⁵ V K^─1.

Abstract: Germanium–Antimony–Telluride (Ge–Sb–Te) has low electrical resistivity and thermal conductivity for good thermoelectric properties. The Ge–Sb–Te thin films were deposited on Al₂O₃ ceramic substrate by pulsed–dc magnetron sputtering system using a 99.99 % Ge:Sb:Te of 1:1:1 composite target and annealed at 573, 623, 673, and 723 K for 1 hour in vacuum. The phase identification, atomic composition, morphology and film thickness (d), carrier concentration (n), mobility (µ), Seebeck coefficient (S) and electrical resistivity (ρ) of the as–deposited and the annealed samples were investigated by X–ray diffraction (XRD), energy dispersive X–ray spectroscopy (EDX), field–emission scanning electron microscopy (FE–SEM), Hall–effect measurement, steady state method and calculation of from n and µ, respectively. The results demonstrated that the as–deposited Ge–Sb–Te film showed amorphous phase and annealing changed the phase crystalline. Morphologies of annealed Ge–Sb–Te films showed very large grain size and porosity to obtaining good n and µ. The approximately maximum power factor (P) was 4.22×10⁻⁴ W m⁻¹ K⁻² at annealing temperature of 723 K.

Abstract: In this work, cobalt oxide thin films were prepared by electrostatic spray deposition (ESD) technique. The influence of the substrate temperatures on properties of film was investigated. Phase transformation of cobalt oxide thin films due to the effect of different substrate temperature was also observed. Cyclic voltammetry was used to measure the performance of cobalt oxide supercapacitor. At higher substrate temperature, the cobalt oxide thin films exhibit the high specific capacitance due to the effect of phase transformation in cobalt oxide films.

Abstract: A simple method was achieved to develop a coating of silver nanoparticles on paper using ultrasonic radiation. Silver nanoparticles were prepared by the chemical reduction method using triethylene glycol as a reducing agent. UV-Vis spectrometry was used to characterize the synthesized silver nanoparticles in solution. The coated papers were characterized the surface features by scanning electron microscopy (SEM) and energy dispersive spectrum (EDS). The particle size distribution was 78 – 311 nm in diameter depending on ultrasonication time. The coated papers revealed the most effective in the antibacterial activity against both Staphylococcus aureus ATCC 25923^Tand Escherichia coli ATCC 25922^T.

Abstract: Manganese oxide thin film sandwiched between carbon nanotubes thin films-coated on fluorine-doped tin oxide (FTO/CNT/MnO_x/CNT) was used as a counter electrode of dye-sensitized solar cell (DSSC) for performance improvement. The multi-layer electrodes were fabricated by sequential process comprising doctor-blade coating of CNT layer and the following electroplating coating of MnO_x layer and subsequent doctor-blade coating of CNT layer once again. The multi-layered counter electrode of CNT/MnO_x/CNT exhibited the improved conversion efficiency and a fill factor of 2.01±0.01% and a fill factor of 0.55±0.01, respectively, due to an increase in capacitance of the electrode. Electrochemical impedance spectra (EIS) show that the capacitance of multi-layered CNT/MnO_x/CNT electrode increased from 22±3 mF to 41±2 mF comparing to that of a monolayer of CNT. Furthermore, EIS of FTO/CNT/MnO_x/CNT-based DSSC shows the smallest radius of the semicircle with a charge transfer resistance of 42 Ω, implying a quick redox reaction between counter electrode and electrolyte. The improved fill factor is likely due to the role of MnO_x that increases the capacitance of electrode and reduces electron transfer rate from counter electron to electrolyte.

Abstract: Manganese oxide (MnO_x) thin films were prepared on stainless steel (SS) 304 by galvanostatic (GS) mode of electrodeposition technique using different precursors; 0.1 M potassium permanganate (KMnO₄) and 0.1 M manganese sulfate (MnSO₄) solutions. The electrodeposition condition was set at a constant current of 1 mA/cm². Different precursors provide MnO_x thin films with different morphologies. Using KMnO₄ as a precursor, the MnO_x thin film was deposited (MnO_x-K), while using MnSO₄ as a precursor, the MnO_x nanosheets with a thickness of approximately 40 nm were formed (MnO_x-S). XPS results evidence the formation of manganese oxide with different oxidation states composition by different precursors. Electrochemical measurements were carried out in a three-electrode setup using Pt and Ag/AgCl electrodes as counting and reference electrodes, respectively and 1M Na₂SO₄ aqueous solution as electrolyte. MnO_x-K at a deposition time of 10 min shows the highest specific capacitance of 233.55±19.01 F/g. The specific capacitance improvement of MnO_x-K may be attributed to MnO_x nanosheet structure which increases surface area of electrode.

Abstract: Abstract In this work, the low-temperature H₂-sensing properties of palladium (Pd) and palladium oxide (PdO) nanoparticles decorated titanium dioxide (TiO₂) thin film were studied. The TiO₂ thin films were prepared by the dc reactive magnetron sputtering. The Pd and PdO nanoparticles were sputtered on the top surface of TiO₂ surface in order to enhance the sensitivity to the H₂ gas. Morphologies, crystal structures, and chemical element of the examiner samples were investigated by the field-emission scanning electron microscopy (FE-SEM), grazing-incident X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS), respectively. The effects of the Pd and PdO nanoparticles on H₂-sensing performance of TiO₂ were investigated over a low concentration range of 150-3,000 ppm H₂ at 50-250°C-operating temperatures. This result exhibited that the PdO decorated on TiO₂ surface showed very high response to H₂ at a low operating temperature of 150°C.

Abstract: Aluminum oxide films were grown on (100) silicon wafers and glass substrates by pulsed dc reactive magnetron sputtering deposition. In this experiment, substrate temperatures were varied from room temperature to 500°C. Grazing-incidence X-ray diffraction (GIXRD) analysis revealed that the resulting films have amorphous structures. Field-emission scanning electron microscope (FESEM) was used to characterize the morphology of the films. The films’ optical properties were determined by UV-Vis spectroscopy. The results demonstrated that the deposition rate, the surface roughness and the transmittance spectra of the aluminum oxide films were strongly influenced by the substrate temperature. The deposition rate and the surface roughness of the films were higher at higher substrate temperatures. In the range between 100°C and 200°C, the transmittance spectra were found to be lower than those of the films deposited at other substrate temperatures. This was due to the sub-aluminum oxide condition in the films. The dependence of films’ optical properties on the substrate temperature might result from the change in chemical compositions during the sputtering process.