Advanced Materials Research Vols. 55-57

Abstract: A silver film was deposited on silicon wafer by DC unbalance magnetron sputtering system. The temperature dependence of the silver film was investigated. The spectroscopic ellipsometry (SE) with the heating of sample stage (HTC100) was employed for the in situ SE measurement under annealing cycles of the sample from room temperature to 300°C in dry nitrogen gas. The results show that the pseudo dielectric constants (<ε1>, < ε2>) of the sample varied with an annealing temperature. The real part of pseudo dielectric constant (<ε1>) of annealed Ag film was slightly changed and the imaginary part (< ε2>) was strongly increased at a photon energy below the optical band gap (3.5-4.5 eV). Furthermore, the pseudo dielectric constant of imaginary part at low energy region was changed due to the enhancement of crystallinity of Ag film at 300°C. All measured SE spectra were fitted by Drude-Lorentz optical model, the scattering time and resistivity were obtained.

Abstract: This work is to study the diffusion of Al into amorphous silicon (a-Si) thin film at the elevated temperature by in-situ Spectroscopic Ellipsometry (SE). The sputtered a-Si film 60 nm thick on an optically opaque Al (100 nm) layer on silicon wafer was heated in a temperature controlled heating sample stage from room temperature to 300°C and slowly cooled down to room temperature while the dynamic SE data were measured. It was found that the ∆ and Ψ spectra began to change quickly at 200°C until the temperature reached 250°C, then continue to changed very slowly until 300°C. No significant change could be observed while the sample was cooling down to room temperature. The full spectral SE measurements were also taken at every 50°C steps and used to model the diffusion of Al into the top a-Si film. The interface layer due to diffusion was modeled by Bruggeman Effective Medium Approximation (EMA) theory as the mixture of Al and Si.

Abstract: he TiO2 films were prepared by reactive smooth d.c. and pulsed d.c. magnetron sputtering on glass slide substrates. A metallic titanium target was reactively sputtered in a mixture of argon and oxygen. The influence of smooth d.c. and pulsed d.c. discharge power on films thickness, crystallinity, surface morphology, photocatalytic activity (methylene blue degradation) and hydrophilic activity were studied. At pulsed d.c. sputtering, plasma generator has been used to provide the asymmetric pulsed d.c. bias of the target at 100 kHz and pulsed off-time 4016ns. The structures of the films at 100nm and 300nm thick showed nano-grain size structure. The pulsed d.c. mode deposition exhibited a considerably lower surface roughness, but higher grain size compared to the films deposited with the smooth d.c. mode. At film thickness about 300 nm, the XRD peaks indicated that the dominant structure was anatase for which the preferred orientation was in (101) plane. It did not show any definite change of phase between the films deposited in the smooth d.c. mode and the film deposited in the pulse d.c. mode. For the photocatalytic activity, it was clearly seen that the films deposited by smooth d.c. mode showed a higher photocatalytic activity. The hydrophilic activity test, after the films had been irradiated by an ultraviolet light source for 30 min., the smooth d.c. mode films (thickness 300 nm) showed that a water contact angle can be less than 10°. In this study, the TiO2 films of smooth d.c. mode sputtering could be applied for a self-cleaning glass application.

Abstract: An experimental investigation was carried out to study the fabrication of double layers of aramid fiber/alumina/epoxy resin laminate composites using low-pressure technique. To obtain the sample with high wear resistance property, the micron size of alumina particles were added into epoxy resin using the ultrasonic processor. The physical and mechanical properties such as density, hardness, impact test, wear resistance and tensile strength of the composites samples were investigated. Furthermore, microstructures of specimens were also examined by scanning electron microscope (SEM). From the results, it was found that the mechanical properties of double layers laminate composites of aramid fiber/alumina/epoxy resin could improve by using the low-pressure technique.

Abstract: In this work the fabrication of glass-ceramics containing ferroelectric BIT crystals was carried out by incorporation method. The BIT powder was prepared by conventional ceramic method with calcination temperature of 800°C. In order to prepare bismuth titanate glass ceramic by incorporation method, the BIT powder was mixed with 25 - 95 mol% B2O3 as a glass former. The batches were melted in an air atmosphere using an electric furnace, at 1150°C for 15 minutes. After that, the melts were quenched between the stainless steel plates at room temperature. It was found that crystallization of unexpected Bi2Ti4O11 phase occurred in most of the glass – ceramics with the amount of B2O3 less than 70 mol%. This may cause from the evaporation of Bi2O3 during melting. Besides, glass could only be obtained from the melt of 80 mol% B2O3 batch. In this glass, however, the small amount of TiO2 crystals was detected using SEM technique. The glasses with the amount of B2O3 more than 80% shows severe phase separation and crystallization of TiO2 and B2O3. The glasses of 80 mol% B2O3 composition were subjected to heat – treatment processes at 300 to 500°C. It was found that the crystallization of Bi2Ti4O11 phase occurred at 500°C while at 300°C and 400°C the glasses were still amorphous. The maximum dielectric constant (er) of the heat treated glass ceramics was found in the range of 22 – 30.

Abstract: TiO2 thin films have been deposited by reactive DC magnetron sputtering technique to study the effect of total pressure and oxygen partial pressure on structure and hydrophilic properties. The crystal structure and hydrophilic property was measured by XRD and contact angle meter, respectively. The results showed that the films were composed of pure rutile and mixed of anatase/rutile structure dependent on the total pressure and oxygen partial pressure. It was found that all films can perform hydrophilic property. In case of high total pressure, the films showed superhydrophilic property, whereas the films deposited under various oxygen partial pressures with fixed total pressure were all films exhibit superhydrophilic property.

Abstract: Titanium dioxide, TiO2, thin films were deposited on unheated Si (100) wafers by two cathodes sputtering system. However, during the deposition of TiO2 films only one cathode was used. A pure metallic titanium was used as a sputtering target. Argon and oxygen were used as sputtered gas and reactive gas, respectively. TiO2 films were deposited at the argon and oxygen ratio of 1:4 and a total pressure of 5.0 x 10-3 mbar. The distance between the target and the center point of substrate was 12 cm. For each deposition of TiO2 films, the position of substrate was changed every 2 cm on the radial position of the cathode. The deposition time for each deposition was 60 min. The films were characterized by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The XRD results and TEM images show that the crystalline rutile TiO2 films can be successfully deposited on an unheated substrate.

Abstract: he glass ceramics from the PbO-Bi3O2-GeO2 system have been investigated. An excellent transparent glass can be obtained from the stoichiometric (S) composition, Pb3Bi2(GeO4)3, but only by rapid-quenching to give very thin samples. This glass could not therefore be used to make good glass-ceramic samples for measuring the dielectric properties. The A-composition (34.50%PbO :11.49%Bi2O3: 54.01%GeO2) and B-composition (25.90%PbO: 8.63%Bi2O3: 65.47%GeO2) have been prepared to form more stable glasses. These two compositions gave good transparent and thick glass samples. DTA analysis has been used to examine the crystallisation temperatures of all glasses. The controlled heat treatment process has been applied to all crystallisation temperatures and glass-ceramic samples were obtained. It was found that S glass-ceramic contained Pb3Bi2(GeO4)3 and Bi2GeO5 while A glass-ceramic contained only Pb3Bi2(GeO4)3 and was suitable for using in dielectric measurement. B glass-ceramic gave difficulty in identifying the phases. However, it was concluded that the glass-ceramic from this composition had three phases, which are PbGe4O9, PbGeO5 and Bi4(GeO4)3. Since this glass gave no PbO-Bi2O3-GeO2 ternary phase, the dielectric measurement concentrates only on the A glass-ceramic. The frequency dependence of eeee²²²² for the A glass-ceramic sample gave a loss peak at low frequency.

Abstract: Geopolymer matrice Composites are fabricated at room temperature or thermoset in a simple autoclave. After approximately four hours of curing, composite materials exhibit excellent properties. Finding applications of geopolymeric composites in all fields of industry are the hot topics. This paper covers: (i) mechanical properties of fibers: carbon, Saint-Gobain Cemfil/CFV alkali resistance glass (various types), ARG-NEC (Nippon electric Columbia) alkali resistance glass, E-glass for pultrusion, AR glass for pultrusion were evaluated in accordance with Japanese Industrial Standard (JIS R 7601). (ii) properties of geopolymeric matrices: geopolymeric matrices are fabricated from various types of geopolymeric resins that were made at Research Institute of Inorganic Chemistry, Inc., Czech Republic and testing for mechanical properties, and by SEM for structure characterization. (iii) fabrication procedures of geopolymer matrix composites with carbon and other fiber reinforcements. (iv) results of mechanical testing of geopolymer composites, SEM for adhesion between the matrix and reinforcement, and (v) Results and discussion.

Abstract: We propose a new design of the secured packet switching using the nonlinear behaviors of soliton in a micro ring resonator, where the nonlinear penalty of light traveling in the device becomes benefit. The chaotic signals are generated by a Kerr effects nonlinear type of soliton in a micro ring resonator, where the control input power can be used to specify the output filtering signals. Some device parameters are chosen and simulated using the proposed model. Results obtained have shown in good agreement with the practical device behaviors. The potential of using such a device for communication security is performed and discussed. For instance, the packet switching of the chaotic encoding data increases from the chaotic signal encoding of 100 bit/s. Results obtained have shown the potential of using such a proposed device for the tunable band-pass and band-stop filters, in which the packet switching data can be performed and secured.