Key Engineering Materials Vols. 675-676

Abstract: In this work, the nanorod structure of Tin oxide (SnO₂) prepared by glancing angle deposition (GLAD) technique with different O₂ flow rate from 12 to 48 sccm. The surface and Crystal structure of SnO₂ thin films were characterized by scanning electron microscopy (SEM), X-raydiffraction (XRD) and tested toward ethanol gas sensing. Structural characterization showed that the morphological of all SnO₂ thin films prepared with different O₂ flow rates consists of columnar nanorod structures and the nanorod size which are likely to decrease as the O₂ flow rate increases. As the O₂ flow rate increases from 12 to 48 sccm, the crystal structure of SnO₂ nanorods changes from amorphous to crystalline and the crystallinity is improved by the increase of the O₂ flow rate. Gas sensing performances of SnO₂ nanorods have been characterized toward ethanol sensing. It was found that SnO₂ nanorods exhibit n-type conductivity with decreased resistance when exposed to ethanol, which is reducing gas. In addition, sensitivity to ethanol tend to improve as O₂ flow rate increases. Furthermore, the SnO₂ nanorods prepared at O₂ flow rates 48 sccm are detecting ethanol gas at concentrations lower than 50 ppm at operating temperature 250 °C.

Abstract: A highly ordered nanotube TiO₂ was successfully prepared from sputtered Ti metal film using anodization process. Ethylene glycol and ammonium fluoride was introduced as the electrolyte solution. The applied of anodizing voltage was systematically controlled between 20 - 60 volts along fabrication process, respectively. The physical characteristic of the fabricated TiO₂ nanotube including anodizing rate, tube diameter and tube width was investigated through the characterization system as field emission scanning electron microscope (FE-SEM). According to cross-section FE-SEM photograph, the anodizing rate and tube width significantly increases when the anodizing voltage was future increased due to higher the electric field. Moreover, the tube diameter directly depends with the anodizing voltage also. The anodizing voltage provides a significant role on the feature of TiO₂ nanotube. Finally, the fabricated nanotube TiO₂ is potentially promising for Photo-activated application and Nanostructure template.

Abstract: CaMnO₃ (CMO) thermoelectric material is large Seebeck coefficient but high electrical resistivity. To reduce electrical resistivity by adding carbon nanotubes (CNTs) in CMO material and may be decreased Seebeck coefficient. In this work, we simulated electronic structure of CMO and CNTs-added CMO by DV-Xα method to investigation of power factor and enhance the thermoelectric performance. The Seebeck coefficient and electrical resistivity were calculated by Maxwell-Boltzmann distribution and Mott’s law to investigate power factor. The DV-Xa calculated show the energy level and density of state (DOS) of CMO and CNTs-added CMO demonstrated that the energy gap reduces from 3.33 eV to 0.19 eV affect to enhance the power factor of CMO with Seebeck coefficient and electrical resistivity are decreases. The power factor of CNTs-added CMO was increased with increasing CNTs content.

Abstract: Transparent ZnO films were deposited by sol-gel spin coating process. HCl acid was used in the wet etching process to modify its surface morphology that can be used as an anti-reflective layer of optoelectric devices. The effect of etching time on its structure, surface morphologies and optical properties were scrutinized. The overall results indicated that HCl acid has obviously effect on significant change in surface morphologies and its roughness varied in the range of 0.5 nm to 4.9 nm.

Abstract: Titanium chromium nitride (TiCrN) thin films were deposited by reactive DC magnetron co-sputtering. The effect of Ti sputtering current (I_Ti) on the structure of the TiCrN thin films were investigated. The crystal structure, microstructure, thickness, roughness and elemental composition were characterized by glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDS) technique, respectively. The results showed that, all the as-deposited films were formed as a (Ti,Cr)N solid solution. The as-deposited films exhibited a nanostructure with a crystallite size of less than 40 nm. The crystal size decreased from 39.9 nm to 33.5 nm, while the lattice constants increased from 4.139 Å to 4.162 Å, with increasing of the Ti sputtering current. The film thickness and roughness were found to increase from 397 nm to 615 nm and 3.7 nm to 6.3 nm, respectively, with increasing of the Ti sputtering current. The composition of the as-deposited films varied with the Ti sputtering current. Cross section analysis by FE-SEM showed compact columnar and dense morphology as a result of increasing the Ti sputtering current.

Abstract: Tantalum oxide (TaO) thin films were deposited by dc reactive magnetron sputtering at room temperature. A target of tantalum (99.995%) and a mixture of argon and oxygen gases were used to deposit TaO films on to silicon wafers (100) and BK7 glass substrate. The effects of annealing temperature (300–700 °C) on structural, morphology and anti-bacterial properties were investigated. Grazing incident X-ray diffraction (GIXRD), atomic force microscope (AFM) measurements are carried out to identify the crystalline structure, film morphology and surface roughness, respectively. The antibacterial behavior of the tantalum oxide thin films will be discussed in this paper.

Abstract: Titanium dioxide (TiO₂) thin films were deposited over glass slides by using spray pyrolysis technique to inhibit the bacteria growth. The samples were characterized by XRD, AFM methods. The XRD patterns of TiO₂ thin films showed the amorphous titanium dioxide phase (low crystallinity) and AFM images displayed the morphology of the constituted grains seems to be a fibrous microstructure. In this research, Escherichia coli (E.coli) was used as testing bacteria and the photocatalytic of TiO₂ was excited by UV light. TiO₂ thin films showed some antibacterial effect in the halo test.

Abstract: An affordable 6-cm diameter magnetron sputtering source was designed and constructed using a neodymium cylindrical permanent magnet inner stud and an outer ring magnet. Both magnets were set in isolation from a water-cooled disk behind the target. In this work, our magnetron sputtering source was employed to deposit copper thin films by changing the outer magnet ring. The outer magnate ring diameter sizes were 29 mm (I.D.)/39 mm (O.D.) and 30 mm (I.D.)/50 mm (O.D.). At the same applied bias voltage, the discharge current of the magnetron with a big outer magnet was higher than that of one with a small outer magnet. According to XRD pattern and AFM image of copper films, the degree of (111) and (200) orientations and surface roughness were increased in the case of films grown by magnetron with bigger outer magnet. The cross-sectional and plane-view SEM images showed that the grain size and film thickness were increased in the case of films grown by magnetron with bigger outer magnet. These results should be because the radial motion of secondary electron emitted from sputtering in front of target surface was increased with a bigger magnet.

Abstract: Spectroscopic Ellipsometry (SE) was used to analyse the effect of plasma treatment on aluminium oxide thin films. The aluminium oxide thin films were fabricated by reactive DC magnetron sputtering at different operating pressures. The as-deposited thin films were plasma treated at different ambient Ar and O₂ conditions. The prepared samples were investigated for physical microstructures with scanning electron microscopy (SEM) and optical characteristics with ellipsometry. The ellipsometric spectra of the prepared samples were measured in the range of 250 to 1650 nm with the incidence angle of 70 degree. Based on the optical model with the Tauc-Lorentz function, the thickness and the refractive index of the films were determined and discussed. The results showed that the thickness and the refractive index of the aluminium oxide thin films were greatly affected after the plasma treatments. In comparison, the results of those prepared at different operating pressures were also discussed. The SE results were confirmed with those from SEM.

Abstract: An emissive layer, fluorene derivative, was performed for organic light-emitting device properties. The preparation of fluorene derivative thin film by spin coating and convective technique was studied the band diagram of thin films which its properties out as the energy gap (E_g). UV-Visible spectrophotometer has been used to investigate the thin film properties. The results indicates spectacular property which occurs the optical properties, fluorescence in thin film and luminescence as a green light in device that it could be applied as emissive layer for organic light-emitting diodes (OLEDs) since the appropriate work function with cathode and anode, aluminum metal and indium tin oxide layer (ITO), respectively.