Key Engineering Materials Vols. 562-565

Abstract: Ultrathin fibers of PVP/ZnTiO3 composite were prepared through sol-gel processing and electrospinning technique. After calcined of the above precursor fibers at 600°C, the spinel ZnTiO3 nanofibers, with a diameter of 50-150nm, were successfully obtained. The fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fourier transform infrared (FT-IR), respectively. The results displayeded that the morphology and crystalline phase of the fibers were largely influenced by the calcination temperature. The reported strategy will be useful for fabricating one-by-one continuous nanofibers, which are suitable for applications in catalysis, chemical sensors, nanoelectrodes, and nanodevices.

Abstract: The performance of Y-branch waveguide (YBW) modulator which is affected by the fabrication has been researched. The range of Y-branch corner deviation is obtained by analyzing the structural loss of the branch in the YBW which is limited by fabrication resolution. The effects on splitting ratio, mode field and coupling loss of YBW are also discussed through changing the waveguide width. It can be obtained that the difference between the two widths should be less than 0.25μm to meet the requirement of 5% error. And the maximum coupling efficiency can be achieved by adjusting the fabrication of waveguide to change the waveguide mode field. The corresponding fabrication tolerance can be attained based on the analysis.

Abstract: Nowadays, the study of brain function is advanced by implantable microelectrode arrays for they can simultaneously record signals from different groups of neurons regarding complex neural processes. This article presents the fabrication, characterization and use in vivo neural recording of an implantable microelectrode array probe which integrated with electrophysiology reference electrode. The probe was implemented on Silicon-On-Insulator (SOI) wafer using Micro-Electro-Mechanical-Systems (MEMS) methods, so the recording-site configurations and high-density electrode placement could be precisely defined. The 16 recording sites and the reference electrode were made of platinum. Double layers of platinum electrodes were used so that the width of the reference electrode was as small as 6 μm. The average impedance of the microelectrodes was 0.13 MΩ at 1 kHz. The probe has been employed to record the neural signals of rat, and the results showed that the signal-to-noise ratio (SNR) of the novel probe was as high as 10 and the ordinary probe was 3. Among the 16 recording sites, there are 9 effective sites having recorded useful signals for the probe with reference electrode and 6 for the ordinary probe.

Abstract: The ideal Gaussian standing wave field model and the Gaussian standing wave field model under the condition of straight edge diffraction disturbance were established, and computer simulation and numerical analysis were done to the two kinds of models. It is concluded that the center position of Chromium atomic sedimentary grating in the straight edge diffraction disturbance standing wave will be away from the diffraction edge; near the given ideal deposit position, the PTVH(Peak to Valley Height) of Chromium atomic sedimentary grating in the ideal standing wave is higher than that in the straight edge diffraction disturbance standing wave, and the FWHM(Full Width at Half Maximum) is also narrower than in the ideal standing wave; for the exist of straight edge diffraction the size of the acceptable sedimentary pattern will be smaller, which has theoretical guidance on the practical operation.

Abstract: ~50 μm single crystal graphene with hexagonal flower shape was synthesized on copper foils by low pressure chemical vapor deposition (LPCVD). The strong influence of Cu foils annealing on suppressing the nucleation of graphene was observed. Scanning electron microscopy (SEM), Optical microscopy (OM), and Raman spectrum showed that single crystal graphene as grown was monolayer with high quality. Suppressing nucleation through an annealing procedure offers an promising way to grow large-scale single crystal graphene controllably.

Abstract: Controlled synthesis surface-clean monolayer graphene was achieved. Monolayer Graphene was achieved by mechanical exfoliation (ME) and chemical vapor deposition (CVD),and then transferred to SiO₂ (300nm)/Si substrates. There were tape residues left on the surface of the ME graphene, and poly (methyl methacrylate) (PMMA)/photoresist residues left on the surface of the CVD graphene after the transferring and lithography process. Annealing method was used to clean all these kinds of residues. Annealing processes were performed at different temperatures in both vacuum and N₂/H₂. It is conclude that N₂/H₂ is crucial for the removing of residues, and 400°C is favorable for removing the residues. Atomic force microscope (AFM) images and Raman spectra were taken to confirm the effect of the annealing.

Abstract: With the continuous increase of the hard disk drive capacity, higher requirements are set for hard disk substrate to minimize roughness and defects of the polished surface. Recently, abrasive-free polishing (AFP) has attracted a great deal of attention due to AFP has fewer micro scratches and better cleaning ability than traditional chemical mechanical polishing (CMP). Our present work investigates the effectiveness of Cu (Ⅱ) as a catalyst for hard disk substrate AFP with H2O2 employed as an oxidizer. Polishing slurries used in AFP on hard disk substrate include deionized water, dispersant and oxidizer. The polishing experimental results show that the slurry of H2O2/Cu(Ⅱ) system has higher material removal rate (MRR) than H2O2 system in abrasive-free polishing on hard disk substrate. Further, the catalytic reaction mechanism of Cu (Ⅱ) in AFP of hard disk substrate was investigated. Compared with the H2O2 system, electron spin-resonance spectroscopy (EPR) analysis shows that the H2O2/Cu(Ⅱ) system provides higher concentration of hydroxyl radical. Potentiodynamic polarization measurements shows that corrosion currents (icorr) of disk substrate in the H2O2/Cu(Ⅱ) system is larger than that in the H2O2 system. The results imply that Cu (Ⅱ) as a catalyst for hydrogen peroxide system possesses promising prospects in abrasive-free polishing.

Abstract: During the fabrication process of metal microdevice by SU-8 UV-LIGA technology, due to the poor adhesion strength between SU-8 photoresist and metal substrate it is common for interface separated and bind failure. In this paper pull-off test, scratch test and indentation test were performed to evaluate the adhesion property between SU-8 photoresist and metal substrate, and the feasibility of these three methods was compared. The result shows that the pull-off test fails to evaluate real interface adhesion strength because of the great possibilities of mixed debond appearance which makes the experimental data discrete and inaccurate. The scratch test and the indentation test can efficiently and accurately evaluate the interface adhesion strength between SU-8 photoresist and metal substrate and are demonstrated two preferable methods.

Abstract: A new type of micro super-capacitor with high working voltage, high over loading, small bulk, and low impedance was fabricated by a new process. The hydrous ruthenium oxide powder was prepared in a solution of RuCl₃·xH₂O and NaHCO₃. Different composites loaded with certain amount of carbon black were synthesized with this technique. Super-capacitor performance was assessed via cyclic voltammetry (CV), charge-discharge studies (DC), and impedance analysis (AC). The results show that the capacitance and resistivity of ruthenium oxide materials were dependent on the sample annealing temperature. The materials heated at 300°C exhibit the highest rate capacitance of 1080 F·g-1. Four to six cells of this capacitor was stacked up in series by conductive films in order to achieve higher working voltage. After packaged in resin, charge/discharge studies and impedance analysis were tested via the electrochemical test system. In the research, super-capacitors with a four-layer structure exhibited fine electrochemical characteristics with high working voltage over 5.5 V and low impedance under 1.5 ohm. Also, it had the ability of high-rate discharge performance and considerable large capacitance.

Abstract: As pitch of TSV shrinks down, mechanical characteristics of TSVs become more complicated and the heat of chip becomes a critical issue. The objective of this paper is to study thermal mechanical characteristics of ultra-fine pitch TSV. The thermal-mechanical characterization of an ultra-fine pitch chip is simulated with FEA.