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As a major step in the conduction of heat dissipation, wafer bonding significantly contributes to device reliability. This work presents the Cu–Sn eutectic bonding with a Mo buffer layer for light emitting diodes to increase its reliability. The conventional Ag-paste bonding and Cu–Sn bonding (without Mo top layer) are also studied for comparison. Their reliability is measured using thermal shock treatments ranging from − 40 to 120 °C (200 cycles). Experimental results indicate that the eutectic bonding with a Mo buffer layer demonstrates a better device performance than the other two counterparts. Following thermal shock treatment, the light droops for the Ag-paste, Cu–Sn, and Mo/Cu–Sn bonding samples are 15, 11 and 7%, respectively. Additionally, the increasing ratios of thermal resistance are 26, 33 and 19%, respectively. Moreover, adding the Mo buffer layer can relieve the thermal stress problem, owing to the thermal expansion mismatch in Gallium–Nitride/Cu–Sn/submount wafer bonding structures.

Traditional white light light-emitting diode (LED) encapsulation is performed by mixed phosphors and silicone coating on LED die. However, this encapsulation with silicone coating incurs overheated temperatures and yellowing problem. Therefore, this work attempts to replace silicone paste by using spin-on-glass (SOG) materials. Experimental results indicate that although initial brightness of SOG-based packaging is lower than that of silicone packaging, its light attenuation is significantly lower than that of silicone for a long lighting time. After the LED power is turned on for 12 h, the brightness of LED with silicone and SOG material packaging decreases from 84 to 48 lm and 73 to 59 lm, respectively. Therefore, SOG material provides an alternative packaging solution for high power LED lighting applications.

In this study, SiOx layers were fabricated by spray pyrolysis deposition (SPD) and aerosol spraying as diffusion barriers between the stainless steel (SS) substrate (SUS430) and the molybdenum back contact layer in CuIn1-xGaxSe2 (CIGS) thin-film solar cells. SPD and aerosol spraying for SiOx layers are attractive processes for the deposition of thin films due to their low cost and controllable properties especially for solar cells on SS foils since a good barrier layer is required to prevent the Fe impurities (ions) defusing from SS substrate to the cells. The properties of SiOx barriers including thermal stability, microstructure content, electrical insulation and thickness of SiOx layers were investigated. The surface morphology and surface roughness were observed by scanning electron microscope and atomic force microscope. A transmission electron microscopy and X-ray diffractometer are adopted to measure the microstructural characteristics, grain size, and residual stresses of films. The chemical composition of the dielectric barriers was analyzed by X-ray photoelectron spectroscopy. The experimental results shows the specific thickness at 200 nm of SiOx layer will cause the absorber layer has the single chalcopyrite phase structure with (112) preferred orientation. The effects from the results revealed that the cells with a SiOx barrier layer fabricated by aerosol spraying provided a promising process in obtaining better CIGS cell performance.

Mixed alloy Cu–In–Ga precursors were deposited from Cu–Ga alloy and Indium targets by the DC magnetron co-sputtering method. There were four crystallization phases, In, CuIn 2 , Cu 11 In 9 and Cu 3 Ga, identified in the precursor after deposition. A large grain-size CIGS film was achieved by controlling the annealing period for selenization and utilizing a two-stage selenization process for secondary crystallization during rapid thermal annealing process. As the annealing temperature increased, the phase transitions moved toward the Cu-rich inter-metallic phases. In addition, the phase transition, stoichiometric ratio and surface-morphology were modified by Ar-ion plasma etching process of the precursors. The results show that after the ion etching process, the precursors can be transferred into a single Cu 11 In 9 crystallization phase and the number of crevices increased due to the soft texture of indium on the surface of the precursors. Finally, CIGS films with good crystalline properties were achieved after a suitable selenization process of only 1-stage.

This study reports the electrochemical mechanical polishing (ECMP) technique for 430 stainless steel (SS) substrate to improve the conversion efficiency of hydrogenated amorphous silicon (a-Si:H) thin-film solar cells. The surface roughness of the untreated 430 SS substrate was ∼38 nm and decreased to ∼23 nm after ECMP processing of the 430 SS substrate. The average diffuse reflection rate decreased from 4.2% of the untreated 430 SS substrate to 1.1% for the ECMP processed 430 SS substrate. The analysis of chemical composition of passive layer on the ECMP processed 430 SS substrate was carried out by the X-ray photoelectron spectroscopic. The passive layer of ECMP processed 430 SS substrate is composed of Cr 2 O 3 and Fe 2 O 3 . The SIMS result indicated that the diffusion of iron (Fe) and chromium (Cr) impurities from the 430 SS substrate into the a-Si:H solar cell can be suppressed by the passive layer which was formed by the ECMP process. In particular, the Cr impurity was effectively blocked from diffusing into a-Si:H layer of the ECMP processed 430 SS substrate. The decreased series resistance and increased shunt resistance for the a-Si:H solar cells on the ECMP processed 430 SS substrate, due to a reduction in the Cr and Fe deep-level defect density, resulted in the cell conversion efficiency increasing to 5.4%. The ECMP process provides an available surface treatment technique for achieving high conversion efficiency of a-Si:H thin-film solar cells on a 430 SS substrate.

A three-dimensional composite was prepared from polybenzimidazole and carboxylated multiwalled carbon nanotubes (PBI-MWCNT-COOH). The composite was used to modify gold (Au) electrodes for hydrogen peroxide (H2O2) detection. The carboxylated nanotubes acted as a reducing agent, reacting with H2O2 to form the nanotube peroxy acid MWCNT-COOOH. The peroxy acid in turn oxidized the imine site of PBI to form PBI N-oxide, which could be electrochemically reduced to PBI, resulting in a current signal proportional to the peroxide concentration. Under optimal conditions, the amperometric response to H2O2 was linear for concentrations from 6.25 μM to 10 mM, with high sensitivity (617.3 μA mM–1 cm–2) and rapid response (2.2 s) at an applied potential of −0.37 V. The sensor also displayed high selectivity and excellent stability.

Amorphous indium zinc oxide (a-IZO) thin-film transistors (TFTs) with bottom- and top-gate structures were fabricated at room temperature by direct current (DC) magnetron sputter in this research. High dielectric constant (κ) hafnium oxide (HfO 2 ) films and a-IZO were deposited for the gate insulator and the semiconducting channel under a mixture of ambient argon and oxygen gas, respectively. The bottom-gate TFTs showed good TFT characteristics, but the top-gate TFTs did not display the same characteristics as the bottom-gate TFTs despite undergoing the same process of sputtering with identical conditions. The electrical characteristics of the top-gate a-IZO TFTs exhibited strong relationships with sputtering power as gate dielectric layer deposition in this study. The ion bombardment and incorporation of sputtering ions damaged the interface between the active layer and the gate insulator in top-gate TFTs. Hence, the sputtering power was reduced to decrease damage while depositing HfO 2 films. When using 50 W DC magnetron sputtering, the top-gate a-IZO TFTs showed the following results: a saturation mobility of 5.62 cm 2 /V-s; an on/off current ratio of 1 × 10 5 ; a sub-threshold swing (SS) of 0.64 V/decade; and a threshold voltage ( V th ) of 2.86 V.

Molybdenum (Mo) thin films were deposited on soda-lime glass substrate by using RF magnetron sputtering. As is well known, base pressure in sputtering is a processing parameter for preparing high quality Mo films, in addition to RF power and working pressure. The structure, surface roughness and electrical resistivity of Mo thin films were investigated at three base pressures of 1.8×10-7, 5.8×10-7and 2.7×10-6 torr. Experimental results indicate that the Mo films deposited at a low base pressure of 1.8×10-7 torr exhibit a low electrical resistivity of 8.910-6 –cm, a low root mean square value of roughness of 4.92nm and a stronger peak intensity of (110) plane than that of the other two pressures. This finding suggests that Mo films sputtered at a low base pressure have higher crystallinity, larger grain size, smoother surface morphology and lower electrical resistivity than those sputtered at a high base pressure.

A series of silica-supported ruthenium−zinc catalysts with various contents of zinc were prepared. These catalysts were characterized with temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H2-TPD), and X-ray diffraction (XRD). The reaction of partial hydrogenation of benzene was carried out in a batch reactor at a pressure of 3.36 MPa. The reduction of Ru−Zn/SiO2 catalysts occurs at a much higher temperature, as compared to the Ru/SiO2 catalyst. The results suggested that ruthenium and zinc were in close proximity with each other. The reduction process of ruthenium oxide was retarded because of Ru−Zn interaction. The profiles of H2-TPD for Ru−Zn/SiO2 catalysts show two desorption peaks. The total amount of desorbed hydrogen decreased with an increase in the zinc concentration. The catalytic activity also decreased with an increase of the zinc concentration in the catalyst. The area of the low-temperature H2-TPD peak, in contrast, increased with an increase of the zinc ...

A series of ultrafine Ru−Zn catalysts have been prepared with direct reduction and hydroxide methods with various Ru/Zn ratios. Sodium borohydride was used as a reducing agent to avoid the agglomeration problem posed by the high reduction temperature when using hydrogen as a reducing agent. The preparation method has a great effect on the composition and surface area of the catalyst. The catalysts prepared with the hydroxide method gave a lower surface area. However, it showed high activity of benzene disappearance. The performance of Ru−Zn catalysts prepared with the hydroxide method display a more distinctive behavior in benzene hydrogenation upon variation of the atomic ratio of ruthenium to zinc. The catalysts prepared with the hydroxide method were more selective to cyclohexene than those prepared with the direct reduction method. The Ru/Zn ratio also has a great influence on the selectivity to cyclohexene.

A series of binary oxide-supported ruthenium catalysts with zinc oxide as a component of the support was prepared. Zinc oxide was a major component of the support, the other component was lanthanum oxide, zirconium oxide, chromium oxide, barium oxide, gallium oxide, strontium oxide, calcium oxide or magnesium oxide. Liquid phase hydrogenation of benzene to cyclohexene was studied on these catalysts in a stirred tank reactor at a hydrogen pressure of 2.5–6.0 MPa and 448 K. The reaction was operated in a kinetic-controlled regime. In order to have high selectivity to cyclohexene, a large amount of water should be present. In addition, the reaction medium should be an alkaline solution. The yield of cyclohexene was in the order: Ru/Ga2O3–ZnO > Ru/La2O3–ZnO > Ru/Cr2O3–ZnO > Ru/ZrO2–ZnO > Ru/MgO–ZnO = Ru/CaO–ZnO = Ru/SrO–ZnO = Ru/BaO–ZnO.Ru/Ga2O3–ZnO demonstrated the highest selectivity and yield of cyclohexene. A model of the low solubilities of reactants in the water film surrounding the catalyst can explain the reaction behavior of the catalyst. © 2001 Society of Chemical Industry

In this study, the CuIn(Ga)Se2(CIGS) crystalline quality and MoSe2thickness of films produced by the rapid thermal selenization process under various selenization pressures were investigated. When the selenization pressure increased from 48 Pa to 1.45 × 104 Pa, the CIGS films were smooth and uniform with large crystals of varying sizes. However, the MoSe2thicknesses increased from 50 nm to 2,109 nm, which created increased contact resistivity for the CIGS/MoSe2/Mo structures. The efficiency of CIGS solar cells could be increased from 1.43% to 4.62% due to improvement in the CIGS crystalline quality with increasing selenization pressure from 48 Pa to 1.02 × 103 Pa. In addition, the CIGS crystalline quality and MoSe2thickness were modified by the pressure released valve (PRV) selenization process method. The crystalline qualities of the CIGS films were similarly affected by the selenization pressure at 1.02 × 103 Pa in the PRV selenization method and the MoSe2thicknesses were reduced from 1,219 nm to 703 nm. A higher efficiency of 5.2% was achieved with the thinner MoSe2obtained by using the PRV selenization method.

In this article, we report the fabrication and characterization of molybdenum (Mo) thin films on soda-lime glass substrate grown by reactive RF magnetron sputtering for Cu(In,Ga)Se 2 thin film solar cells. It was found that the growth parameters, such as argon flow rate, RF power, bi-layer of Mo thin films and substrate temperature, have significant influences on properties of Mo films. As the argon flow rate was increased, the sheet resistance of Mo films increase, and the strain were changed from tensile to compressive. Higher RF power leads to a decrease on sheet resistance, and the optimal thickness and sheet resistance are 1 µm and 0.2 Ω/□. In addition, our experimental results proved that the increase of substrate temperature will lead to better adhesion of Mo thin film with glass substrate, and lower sheet resistance (0.11∼0.14 Ω/□).

500 nm-thick aluminum-doped zinc oxide (ZnO:Al) thin film is usually used as a front transparent conductive oxide (TCO) contact on photovoltaic devices, and for this application is often deposited by a reactive radio-frequency (r.f.) magnetron sputtering system from a ceramic target. This work reports on the preparation and characterization of AZO thin films on Corning 1737 glass substrates grown by reactive r.f.-magnetron sputtering from a ZnO ceramic target with 2 wt% Al content. It was found that the growth parameters, such as chamber pressure, working power, and deposition temperature, have significant influences on the properties of AZO films. According to the experimental results: (1) Films were polycrystalline showing a strong preferred c-axis orientation. (2) With increasing working power, the resistivity decreased, and mobility and the carrier concentration increased. (3) Lower deposition temperature leads to a decrease in resistivity, with 2.5×10-4 Ω-cm representing the lowest resistivity reached.

This work reports on the fabrication and characterization of Mo thin films on soda-lime glass substrate grown by reactive RF magnetron sputtering. Film thickness was measured by x-ray step surface profiler. The structural properties and surface morphology were analyzed by x-ray diffraction (XRD), atomic force microscope (AFM) and scanning electron microscopy (SEM). Electrical properties were measured by four-point probe. It was found that the growth parameters, such as argon flow rate, RF power, film thickness, have significant influences on properties of Mo films. The strain on films revealed the complicated relationship with the working pressure, which might be associated with micro structures and impurities. In order to improve the adhesion and electricity, we adopted a two-pressure deposition scheme. The optimal thickness and sheet resistance are νm and 0.12 ω The mechanisms therein will be discussed in detail. Furthermore, we also investigated the diffusion property of Na ion of double Mo films sputtered on soda-lime glass. Our experimental results could lead to better understanding for improving further CIGS-based photovoltaic devices.

The efficiency of CIGS (Copper Indium Gallium diSelenide) solar cells fabricated on stainless steel foil is lower than that on soda-lime glass substrates due to the lack of sodium incorporation and metal impurity diffusion. A dielectric barrier is necessary to prevent metal impurity diffusion for stainless steel substrates. Spin-on-glass (SOG) coatings are characterized by their lower cost and larger area than other vacuum deposition methods. By using spin coating SOG to deposit SiOx barrier layers, this study investigates the characteristics of their insulation and impurity barrier. For insulation property, a higher curing temperature is preferred. The insulation does not further improve when the curing temperature exceeds 400 °C. The SiOx film resistance can be as high as 108 Ω when the voltage is smaller than 10 V. For impurity barrier characteristics, although thick thickness is preferred, it easily incurs thermal cracking. To effectively barricade metal impurity diffusion, the influence of SiOx thick...

CIG precursors were deposited on the glass from the Cu-Ga alloy and Indium targets by co-sputtering method. The results show that when the sputtering pressure was increased, the surface morphology was changed from a roughness island-crystalline (RMS=165 nm) to a smaller pellet-crystalline (RMS=54.4 nm). At the same time the Cu/(In+Ga) ratio was increased. So, the crystallization of Cu11In9 phase was increasing and CuIn2 phase was decreasing in the CIG precursor. Then, a layer of selenium was coated on the precursor and the precursor was selenized using RTA selenization of 600 °C. The results show a good stoichiometric and crystallization under the parameters of the sputtering pressure at 4.2 mTorr of CIG precursors.