Thickness dependence of grain size and surface roughness for dc magnetron sputtered Au films

The grain size and surface morphology of sputtered Au films are studied by x-ray diffraction and atomic force microscope. For as-deposited samples the grain growth mechanism is consistent with the two-dimensional （2D） theory, which gives relatively low diffusion coefficient during deposition. Annealing process demonstrates the secondary grain growth mechanism in which the thickness dependence of grain boundary energy plays a key role. The surface roughness increases with the increase of grain size.

Preparation and Characterization of Sol-Gel Derived Au Nanoparticle Dispersed Y_2O_3∶Eu Films

Gold nanoparticles dispersed Y2O3 films were prepared through a sol-gel method by using yttrium acetate and Au nanoparticles colloid as precursors. The films were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and UV-VIS absorption spectra. XRD patterns and TEM images of Y2O3 ＋ Au films give the same resuits on structure and particle size as that of pure Y2O3 films. The surface plasma resonance （SPR） of Au nanoparticles in Y2O3 ＋ Au film was observed around 550 nm in the absorption spectrum and its position shifts to red with increasing annealing temperature is caused by the increase of dielectric constant of Y2O3 matrix and the size of Au nanoparticles. The second and third order nonlinear optical effects of Y2O3 ＋ Au films were also observed. The photoluminescent properties of Y2O3 ： Eu ＋ Au films were investigated and results indicate that there exist an energy transfer from Eu^3 ＋ to Au nanoparticles and this energy transfer decreases the emission of Eu^3 ＋ in Y2O3 ： Eu ＋ Au film.

Comparison the Theoretical and Experimental Results of Radio Absorbing Properties of Au Thin Films in 8-11.6 GHz Band

The comparison of theoretical and experimental results of measurements of absorbing properties of Au films of 10 nm thickness deposited on a polymer substrate in the frequency band 8-11.6 GHz electromagnetic radiation are presented. The new configuration of Au thin film in a rectangular waveguide had been considered. An abnormally high level of absorption of electromagnetic radiation throughout the range of wavelengths was obtained. This is apparently due to the lack of galvanic contact between the film and waveguide.

The effect of magnetic impurity scattering in Au films

The magnetic impurity scattering plays an important role in the phase coherence behavior of thin films.By using the thickness and disorder dependences of the low temperature logarithmic anomaly in resistivity we are able to determine the concentration of magnetic impurities in Au films and demonstrate that the low temperature saturation or plateau in phase decoherence time is closely related with the Kondo effect.

Free-standing two-dimensional Au films

Free-standing two-dimensional(FS-2D) materials of covalent or ionic bonds can be prepared through mechanical exfoliation by virtue of their intrinsic layered crystal structures.Here,following this strategy,it was reported the fabrication of large-area FS-2D Au films with controllable lattice orientations via an electrochemical hydrogen-detaching method.It was further characterized the catalytic properties of FS-2D Au.The(111)-oriented FS-2D Au with 20 nm in thickness shows a catalytic conversion up to 43.8% for the oxidation of cyclohexane as a model reaction system,a result of more than double of generally reported values.The exceptionally high catalytic activity could be attributed to the flexible structure of the FS-2D Au catalyst,which differs from the rigid structure of general catalysts.The results give useful implications for large-scale productions of a variety of FS-2D metals with controllable orientations,by which their applications may not be confined to catalysis chemistry.

Enhanced nonlinear optical absorption of Au/SiO_2 nano-composite thin films

Nano metal-particle dispersed glasses are the attractive candidates for nonlinear optical material applications. Au/SiO2 nano-composite thin films with 3 vol% to 65 vol% Au are prepared by inductively coupled plasma sputtering. Au particles as perfect spheres with diameters between 10 nm and 30 nm are uniformly dispersed in the SiO2 matrix. Optical absorption peaks due to the surface plasmon resonance of Au particles are observed. The absorption property is enhanced with the increase of Au content, showing a maximum value in the films with 37 vol% Au. The absorption curves of the Au/SiO2 thin films with 3 vol% to 37 vol% Au accord well with the theoretical optical absorption spectra obtained from Mie resonance theory. Increasing Au content over 37 vol% results in the partial connection of Au particles, whereby the intensity of the absorption peak is weakened and ultimately replaced by the optical absorption of the bulk. The band gap decreases with Au content increasing from 3 vol% to 37 vol % but increases as Au content further increases.

EFFECT OF LASER INPUT ENERGY ON AuSn_x INTERMETALLIC COMPOUNDS FORMATION IN SOLDER JOINTS WITH DIFFER-ENT THICKNESS OF Au SURFACE FINISH ON PADS

Formation of AuSnx intermetallic compounds （IMCs） in laser reflowed solder joints was investigated. The results showed that few IMCs formed at the solder/0. 1μm Au interface. Needlelike AuSn4 IMCs were observed at the solder/0.5μm Au interface. In Sn-2.0Ag-O,75Cu-3,0Bi and Sn-3.5Ag-O.75Cu solder joints, when the laser input energy was increased, AuSn4 IMCs changed .from a layer to needlelike or dendritic distribution at the solder/0.9μm Au interface. As for the solder joints with 4.0 μm thickness of Au surface finish on pads, AuSn4 , AuSnx, AuSn IMCs, and Au2Sn phases formed at the interface. Moreover, the content of AuSnx IMCs, such as, AuSn4 and AuSn2, which contained high Sn concentration, would become larger as the laser input energy increased. In the Sn-37Pb solder joints with 0.9 μm or 4.0 μm thickness of the Au surface finish on pads, AuSn4 IMCs were in netlike distribution. The interspaces between them were filled with Pb-rich phases.

Effect of annealing on composition,structure and electrical properties of Au layers grown on different thickness Cr layers

110 nm-thick Au layers were sputter-deposited on unheated glasses coatedabout a 10 nm-thick and a 50 nm-thick Cr layer respectively. The Au/Cr bilayer films were annealedin a vacuum of 1 mPa at 300℃ for 2, 5 and 30 min, respectively. Auger electron spectroscopy, X-raydiffraction and Field emission scanning electron microscopy were used to analyze the composition andstructure of the Au layers. The resistivity of the bilayer films was measured by using four-pointprobe technique. The adhesion of the bilayer films to the substrate was tested using tape tests. Theamount of Cr atoms diffusing into the Au layer increases with increasing the annealing time,resulting in a decrease in lattice constant and an increase in resistivity of the Au layer. Thecontent of Cr inside the Au layer grown on the thinner Cr layer is less than that grown on thethicker Cr layer. For the Au/Cr bilayer films, the lower resistivity and the good adhesion to theglass substrate can be obtained at a shorter annealing time for a thinner Cr layer.

Femtosecond laser ablation of Au film around single pulse threshold

Ablation process of 1-kHz femtosecond lasers （pulse duration of 148 fs, wavelength of 775 nm） of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D^2 of the ablated craters and the laser fluence Ф0. From the plot of the accumulated laser fluence NCth（N） and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.

Improvement in the Adhesion Between Electrode of a SOFC and Ag Paste as a Current Collector by Au Deposition

This paper reports the use of Au films to improve the performance of the stacked solid oxide fuel cell(SOFC) based on the characterization of the interface and the adhesion between the electrodes of the SOFCs and the Ag paste. The specimens were manufactured to perform the experiment as follows. A Si O2 wafer with a 300 mm notch was attached to the electrodes of a SOFC by a Ag paste and Au film, which were deposited on the electrodes by sputtering for 1 min or 5 min deposition time and annealed at300 C for 1 h. The four-point bending test was performed, which resulted in the formation of an extended crack at the tip on the wafer notch, and the crack propagation was observed using a stereo microscope equipped with a charge-coupled device(CCD). Consequently, the interfacial adhesion energy and the effect of the Au film between the each electrode and the Ag paste can be evaluated. On the cathode, the interfacial adhesion energy without Au film was 2.59 J/m2(upper value) and the adhesion energy increased to 11.59 J/m2(upper value) and 15.89 J/m2(lower value) with the Au film. On the anode,the interfacial adhesion energy without Au film was 1.74 J/m2(upper value), which increased to 11.07 J/m2(upper value) and 14.74 J/m2(lower value) with the Au film. In addition, the interface areas were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) to estimate the interface delamination.