Key Engineering Materials Vols. 645-646

Abstract: The anisotropic silicon etching characteristics of TMAH(tetramethyl ammonium hydroxide)+Triton at near the boiling point were investigated. The etch rate of Si {100}, the convex corners, and the roughness of the etched surface contact with the fabrication of bulk microstructures and thus micromechanical devices in silicon. This study presents that the etch rate of Si {100} in 25 wt.% TMAH with 0.1% Triton at near boiling point (112°C) is 1.37μm/min, it is three times higher than it at 80°C. The surface roughness and convex corners of Si {100} after etching at different temperature were investigated by optical microscope, scanning electron microscope (SEM) and atomic force microscope (AFM). The etching rate and smoothness of an etched surface can be improved simultaneously at near boiling point, meanwhile, the undercutting on convex corner should be accepted.

Abstract: Hierarchically ordered macro-/mesoporous carbon (HOPC) was synthesized via a dual-template approach and used as the host matrixes to design the host-guest energetic composites. Monodisperse silica colloidal crystals were used as a hard template, amphiphilic triblock copolymer Pluronic F127 as a soft template, and soluble resols as a carbon source. The obtained HOPC is composed of highly ordered fcc macropores (225 nm), interconnected macropore windows (40 nm), and large mesopores (11.6 nm), resulting in high surface area (503.6 m2/g) and large pore volume (0.833 cm3/g). A high energy material (CL-20) had been encapsulated in HOPC by impregnation process, and the maximum loading amount was around 63 wt.%. The synthesized CL-20/HOPC host-guest energetic composites exhibit much lower thermal decomposition temperature than that of pure CL-20 and their physical mixture.

Abstract: An embedded SiGe layer was applied in the source/drain areas (S/D) of a field-effect transistor to boost the performance in the p channels. Raised SiGe S/D plays a critical role in strain engineering. In this study, the relationship between the SiGe overfilling and the enhancement of channel stress was investigated. Systematic technology computer aided design (TCAD) simulations of the SiGe overfill height in a 40 nm PMOS were performed. The simulation results indicate that a moderate SiGe overfilling induces the highest stress in the channel. Corresponding epitaxial growth experiments were done and the obtained experimental data was in good agreement with the simulation results. The effect of the SiGe overfilling is briefly discussed. The results and conclusions presented within this paper might serve as useful references for the optimization of the embedded SiGe stressor for 40 nm logic technology node and beyond.

Abstract: Uniform films of silver nanoparticles (Ag NPs) were fabricated by self-assembly on 3-aminopropyltriethoxysilane (APTES) and [3-(2-aminoethyl) aminopropyl] trimethoxysilane (AEAPTES) modified glass slides. A stable Ag NPs suspension was synthesized via the reduction of silver nitrate using sodium citrate. Bulk characteristics of Ag NPs in aqueous solution were carried out by measuring their absorption spectrum, morphology and particle shape using the UV-vis absorption spectroscopy and transmission electron microscopy (TEM), respectively. The average diameter of Ag NPs is about 50 nm. The coverage of adsorbed particles on the modified glasses was measured by scanning electron microscopic imaging (SEM). The SEM images indicate that the Ag NPs films on the glasses are uniform. It is supposed that the adsorption processes are mainly controlled by electrostatic interactions. The adsorption amount of Ag NPs on APTES modified glass slides is much more than the amount on AEAPTES modified glass slides.

Abstract: This paper reports a W-band solid-state quadrupler based on multi-chip module and nonlinear schottky barrier diodes. The quadruple consists of Q-band doubler and amplifier, branched-guide coupler and two parallel W-band doublers that are power-combined in-phase using T-juntion at output waveguide, and each W-band doubler channel includes two schottky barrier diodes featuring two anodes on a 127um-thick quartz substrate. The power-combined strategy decreases the size of W-band quadrupler to 56mm×33mm×20mm and increases the maximum stable output power by twice with regard to the traditional W-band doubler. The measured output power of the quadrupler is greater than 20mW over the 80 to 90 GHz and 40mW within 80.6 to 86.6 GHz with above 12% 3dB bandwidth when driven with 2mW input power at 300K. The spectrum of output signal is tested and analyzed to obtain the purity and noise performance of signal.

Abstract: During making the surface acoustic wave devices and integrated circuit hybrid integrated electronics, it needs to put the piezoelectric crystal and silicon wafer bonding together. By selecting a certain wavelengths of UV curing adhesive, then exposing with 300-436nm wavelength of exposure machine, 8mm×8mm bonding chips are got. Bonding LiNbO3, quartz and silicon wafer respectively, measured maximum shear force is 116.2 N and 117.9 N with shear force test machine. The fracture energy is 5.831 J/m² measured by crack-opening method test LiNbO3 bonding chips. The results show that piezoelectric crystal and silicon wafer bonding interface level off and the bonding of the middle layer thickness for about 3 microns observed the bonding section with SEM.

Abstract: This paper presents a novel method of quantitative production of charges with a carbon nanotubes (CNTs) coated electrode. It is based on the Trichel pulse (TP) discharge which is characterized as highly regular current pulses. The charge-per-pulse transported in the discharge gap is nearly constant for a given condition. The total charges produced in unit time are an integer times of charge-per-pulse. The amount of charges and production velocity can be easily and quantitatively controlled, which may be of importance for some particular applications, such as electro-fluid-dynamic (EFD) actuator, reaction control in plasma-chemical synthesis and lab-on-a-chip. The effects of humidity and temperature on the charge-per-pulse also have been experimentally investigated and extensively analyzed.

Abstract: In this paper, we investigate the impact of the size of holes in graphene nanomesh. A multiscale simulation framework is utilized to simulate different structures flexibly. These structures include an intact graphene nanoribbon (GNR), a graphene nanomesh with 4 atoms missing periodic (4-atom holes GNM), and a graphene nanomesh with 6 atoms missing periodic (6-atom holes GNM). Simulation results indicate that a subband appears in the conduction band in 6-atom holes GNM. In addition, interface states which come from the interactions among dangling bonds can significantly reduce the bandgaps of GNMs and induce a pinning effect to their Fermi energies.

Abstract: Novel ordered three-dimensional (3D) firtree-like hexagonal cobalt microcrystals with hierarchical dendritic superstructures have been obtained by using cobalt bis (4-pyridine carboxylate) tetrahydrate as the precursor of Co. The 3D dendrite has a main axis and the leaves arrange layer by layer in parallel along the axis, which exhibit the radiate hexagonal arrangement from the axis in a layer. The main axis of the dendrite grows along the [001] direction of hexagonal Co and the leaves grow parallel to the (001) plane. The hysteresis loop of the sample shows a ferromagnetic behavior with the saturation magnetization of 134.0 emu/g and the coercivity of 184.9 Oe. It is noted that the coercivity is relatively low compared with that of the cobalt dendritic crystallites reported previously, which may result from the lower total morphology anisotropy of our sample.

Abstract: Graphene oxide (GO) was prepared by Hummers method and GO/1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) composite was prepared via an ultrasonic compounding method. The structure of GO was characterized using XRD and SEM, the thermal decomposition of HMX and GO/HMX composite was analyzed by DSC/TG test. The results show that interlayer space of GO increases markedly, the thermal decomposition process of HMX can be promoted with the nanolayer structure of GO, resulting the reduced thermal decomposition activation energy of about 50 kJ/mol with 1% GO.