Papers by Keyword: Au

Abstract: In the ultrasonic bonding process, oxides existing on the metal surfaces are removed, and bonding is achieved by bringing clean surfaces to be in contact with each other. However, the bonding process with microstructure variation is not well understood due to experimental difficulties. In this study, using a newly developed sample holder, which enables ultrasonic bonding in a TEM, we directly observed the bonding process at the nanoscale. The bonding process of Au foils with a clean surface was investigated and compared to that of Al foils with a stable oxide film, a bonding inhibitor, on the surface. During the Al ultrasonic bonding process, the nanoparticles generated dispersed over the entire bonding interface and finally formed a fine grain region at the interface. In contrast, in Au bonding, the nanoparticles generated tended to accumulate at the local area of the Au surface and form bridge-like connections between Au foils. It was considered that these differences in bonding behavior were caused by the surface conditions of the materials to be bonded.

Abstract: An investigation of the electrical and microstructural properties of gold (Au)/p-type silicon (Si) contact was performed as a function of rapid thermal annealing (RTA) temperatures. Au films reacted with Si and produced Au₂Si and Au₃Si phases during the deposition of the films at room temperature. The electrical properties of the Au contact to p-type Si degraded with increasing RTA temperature. Such a degradation of the electrical properties could be associated with the degradation of the surface and interface morphology caused by the formation of Au-silicide clusters. The RTA process at 500 °C led to an increase in the size of the Au-silicide Island. This led to the further degradation of the electrical properties after annealing at 500 °C.

Abstract: There were still unclear questions in the new method that fabricate the high quality poly crystalline Si thin film from amorphous Si thin film with lower annealing temperature than conventional Si recrystallization temperature. In that recrystallization process, the recrystallization mechanism was generally explained by the MIC (Metal Induced Crystallization) of Au. In this paper, we have discussed the effects of film structure and strong gravity on recrystallization, by using conventional furnace and high-temperature ultracentrifuge furnace system. The five kinds of samples (two bilayered Si/Au thin films, two multilayered Si/Au thin films and trilayered Si/Au/Si thin film) and found the effects of structure and strong gravity. The best for crystallization was Au/Si multilayered thin film, which is almost finished to crystallize even at 673 K annealing. The strong gravity advanced and retreated the crystallization, depending to thin film structure.

Abstract: This article presents a simple method for fabrication of Au-CdS composite thin films onto indium-tin-oxide (ITO) coated glass substrates. The method starts with electrodeposition of CdS thin films onto ITO substrates and followed by spontaneous growth of Au nanoparticles onto the CdS surface in solutions containing AuCl₄^- ions. X-ray diffraction (XRD) and UV-vis spectroscopy were used to investigate the Au-CdS thin films. The photoelectrochemical property and sensing for Hg²⁺ ions of the Au-CdS/ITO were studied. The electrode exhibits a low limit of detection of 2.5 μM and a high selectivity for Hg²⁺ ions, even in the presence of a large excess (1000-fold) of other metal (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cd²⁺, Pb²⁺, and Zn²⁺) ions.

Abstract: Atmospheric-pressure dielectric barrier discharge (DBD) cold plasma was used to prepare high performance Au/P25 catalysts (Au/P25-P). XRD and UV-Vis DRS spectra for Au/P25 catalysts were performed. The results indicated that the size of Au nanoparticles in Au/P25-P was smaller than that prepared by conventional thermal impregnation method (Au/P25-H). The temperature-dependent CO oxidation was performed to investigate the activity of Au/P25 catalysts. Au/P25-P gave excellent catalytic activity for CO oxidation than that of Au/P25-H. This may be attributed to the smaller size of Au nanoparticles in Au/P25-P.

Abstract: The aim of this work is to report on the preparation of bismuth and gold nanoparticles ablating the corresponding target immersed in different liquid solutions: water and ethanol. The effect of the liquid environment and laser fluence used for ablation on the size and size distribution of the nanoparticles synthesized was investigated. The nanoparticle size was measured by transmission electron microscopy (TEM). In general terms, for both metals, the results obtained reveal smaller sizes as low as approximately 2 nm. The bismuth nanoparticles, as deposited, are highly crystalline in nature and, depending on the conditions of preparation, either Bi or Bi₂O₃ nanoparticles are obtained in both liquids. UV-Vis measurements show the typical band absorption characteristic of spherical particles of nanometric size. It is worth mentioning that the gold colloids obtained using water are very stable.

Abstract: Our work is dedicated for review of the synthesis of the new nanocomposite media with Au and CdS nanoparticles. Also formation of filament structure in presented samples as result of interaction with femtosecond laser pulses in depending on the component composition of the samples and the various experimental conditions was investigated.

Abstract: We report a modification method for Gold target by intense pulsed ion beam (IPIB) irradiation. Based on the temporal and spatial distribution models of the ion beam density detected by Faraday cup in the chamber and the ions accelerating voltage, the energy deposition of the beam ions in Au is calculated by Monte Carlo method. Taking this time-dependent nonlinear deposited energy as the source term of two-dimensional thermal conduction equation, we obtain the temporal and spatial ablation process of metal Au during a pulse time. The top-layer Gold material in thickness of about 0.25μm is ablated by vaporization and the layer in thickness of 1.40μm is melted after one shot at the ion beam density of 300 A/cm2.

Abstract: Au-catalyzed growth of nanocrystalline Si by pulse jet chemical vapor deposition has been investigated. Au thin film was first deposited on thermally oxidized Si(100), then CH₃SiH₃ pulse jets were irradiated onto the Au/SiO₂/Si(100) surface. The irradiation of the CH₃SiH₃ jets at 1150 °C resulted in circular patterns with a diameter of ~40 µm on the sample surfaces. In the center of the circular patterns, agglomerations of Au were observed. It was found that the oxide layer was etched and that nanocrystalline Si with diameters ~500 nm was formed in the circular patterns. These results indicate that the nanocrystalline Si was grown by the VLS process in which Si atoms were supplied from the oxide layer, Si substrate, and CH₃SiH₃ molecules.

Abstract: Transfer printing of Au micro-electrode patterns onto a polyimide (PI) film was investigated, and the optimum transfer conditions were obtained. Here, the line and space patterns with widths of 25 μm and 100 μm were successfully transfered on polyimide films at a molding temperature of 150 °C for 3 min under the molding pressure of 2.5 MPa. This technique is expected to provide simplified processes to fabricate electrode patterns on microelectro mechanical systems (MEMS).