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Zheng X.,Zhejiang University | Wang D.,Zhejiang University | Wang D.,Suzhou Advanced Vacuum Electronic Equipment Co. | Wang W.,Zhejiang University | Zhou Y.,Zhejiang University
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2014

Micro-structured silicon was produced by irradiating the mono-crystalline silicon with 1064 nm semiconductor microsecond pulse laser in air and SF6. The microstructures and optical properties of the laser-irradiated Si were characterized with scanning electron microscope and UV-VIS-NIR spectrophotometer. After Irradiation of 1600 laser pulses, 30 μm-tall conical spikes with a density of formed on the irradiated spot in air and SF6. The surfaces of conical spikesformed in SF6were found to be smoother and have a higher aspect radio (~2) than those formed in air, indicating that when it comes to microstructures formation, SF6 atmosphere is more effective. The average reflectivity of micro-structured silicon produced in SF6 is 2.8%, lower than that of micro-structured silicon produced in air. We suggest that laser-assisted chemical etching and re-deposition have a major impact on formation of the silicon microstructuresby microsecond pulse laser ablation. Source

Wang W.,Zhejiang University | Wang D.,Zhejiang University | Wang D.,Suzhou Advanced Vacuum Electronic Equipment Co.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2014

Here, weaddressed the metallization of negative temperature coefficient (NTC) thermal sensitive ceramics. The multilayered Ni/V-Ag thin films, consisting of a Ni-V transition and diffusion barrier layer (500 nm) and Ag welding layer (200 nm), were deposited successively on substrate of NTC ceramics by magnetron sputtering. The microstructures and interface adhesion of the multilayers and electrical properties of the NTC ceramics were characterized with scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results show that the Ni-layer makes a good Ohmic contact on the NTC ceramics, and significantly strengthens the interfacial adhesion. In addition, the Ni layer ensures a high soldering quality, not only because it effectively prevents Ag from diffusing into bulk ceramics, but al so because it has a high temperature corrosion-resistance in no-lead soldering. ©, 2014, Science Press. All right reserved. Source

Wang W.,Zhejiang University | Wang D.,Zhejiang University | Wang D.,Suzhou Advanced Vacuum Electronic Equipment Co. | Zheng X.,Zhejiang University
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2014

The Cr/Cu films electrode was deposited by dual-target magnetron sputtering on substrate of ZnO varistor ceramics. The impacts of the deposition conditions, such as the pressure, sputtering power, film thickness, and ZnO'ssurface properties, on the formation, microstructures, and properties of the interface were evaluated. The interface was characterized with X-ray photoelectron spectroscopy. The results show thatelectron transfer has a major impact on the formation and properties of the Cr/ZnO interface. For example, at the initial stage, the electron transfer, occurring between Cr's orbitals and surface state of the ZnO substrate, turns the Cr atom into oxidation state, possibly because of penetration and diffusion of Cr atoms into ZnO layer; and as the Cr layer grew, metallicstate of Cr become increasingly dominant in the Cr film, accompanied by a weakening of the electron transfer. The interface reaction of Cr and ZnO, particularly formation of chromium oxide, was found to strongly affect the Ohmic contact, interfacial adhesion, and longitudinal diffusion barrier of Agand/or Cu. Source

He M.,Zhejiang University | Xu X.,Kunshan Wanfeng Electronics Co. | Feng B.,Zhejiang University | Feng B.,Suzhou Advanced Vacuum Electronic Equipment Co. | And 3 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2014

We proposed a novel metallization process for PZT piezoelectric buzzers using direct-current (DC) magnetron sputtering method, and compared it to the traditional screen-printed method Three groups of samples with different sputtering processes were investigated, namely Cr/Cu/Ag, Ti/Cu/Ag and Cu/Ag multilayer structures. The micro-structure of surface and cross-section view of metallized films were analyzed by scanning electron microscopy (SEM), other aspects, such as adhesion and electric characteristics were also investigated. Results show that the performance of films prepared by magnetron sputtering method has surpassed those by screen-printed method in all aspects. The proposed method provides more dense, uniform, and conformal films than the traditional one, and the Ti/Cu/Ag structure shows the best performance owing to the matching of materials between Ti glue layer and PZT substrate. The largest tensile strength reaches 13.5 MPa, and the mean resonant resistance and electromechanical coupling coefficient are 25 Ω and 0.7, respectively, which are better than those of screen-printed ones. Additionally, the thickness of metallized film of magnetron sputtering is only about 1.7 micron that is much less than the screen-printed one. Due to the good performance, low-cost as well as non-pollution, the magnetron sputtering show promising applications in piezoelectric buzzer and other PZT based devices. ©, 2014, Journal of Functional Materials. All right reserved. Source

Jin H.,Zhejiang University | Xu X.,Kunshan Wanfeng Electronics Co. | Tao Y.,Zhejiang University | Feng B.,Zhejiang University | And 3 more authors.
Microelectronics Reliability | Year: 2016

Zinc oxide (ZnO) varistors, which are produced by sintering ZnO powder together with small additives of Bi2O3, Co3O4, Sb2O3 and other oxides, are popular ceramic semiconductor devices and widely used in electric circuits and systems as voltage-clamping or surge-arrester owing to their extremely nonlinear current-voltage characteristics. The reliability of ZnO varistors is the most important consideration, and researches are mainly focus on the material properties of ZnO body and the effects of additives, such as ZnO grain size and the surrounding additive-rich insulating barriers. However, the manufacturing of electrodes still remains the traditional silver baking process, and few people investigate the effects of electrodes on the reliability of devices. In this paper, we propose a novel electrodes manufacture process using magnetron sputtering technology, and investigate the reliability of devices comparing to silver baking process. Two groups of samples with diameters of 20mm were prepared by silver baking and magnetron sputtering process respectively. The nonlinear voltage, nonlinear coefficient, and leakage current parameters were measured by the metal oxide varistor meter typed TTK-168; the energy absorption capacities were measured by a lightning current surge generator with 8/20μs impulse waves; the adhesive strength of electrodes was measured by a dynamometer; the microstructures of the samples were examined using Scanning Electron Microscope, and the change ratio of nonlinear voltages at an environment of 125°C after 100h was chosen as the main reliability parameter. Results show that the sputtered electrodes could improve the reliability of samples by reducing the change ratio from 1.32% to 0.61%, with other parameters exceeding the silver baking samples at the same time. This enhancement is benefit from the good interface between sputtered electrodes and ZnO substrate as well as the low temperature during magnetron sputtering process. © 2016 Elsevier Ltd. Source

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