Key Engineering Materials Vols. 562-565

Abstract: Doping can lead to residual strain and change of elastic properties in silicon. Residual strain makes silicon wafer exhibit curvature, which are used for fabricate MEMS structure. The boron doping profile is not uniform through depth, which makes doped silicon become a inhomogeneous material or Functionally Graded Material. For boron-doped circular single crystal silicon wafer, a analytical method which based on functionally graded plate mechanics theory, is proposed to calculate its curvature. Example was used to verify the analytical method through 3D finite element simulation.

Abstract: With the extensive research and application of SOI nano-optical ring resonators, the problem of high integration becomes the bottleneck restricting its development. To research the effect of deposited SiO2 insulating layer on the resonance characteristic of SOI nano-waveguid ring cavity while integrating, a rib waveguide ring resonator with 500nm SiO2 insulating layer deposited was designed and fabricated in this paper. By testing the resonance transmission spectrum power of this structure, it is found that SiO2 insulating layer deposited has no effect on the grating vertical coupling efficiency while improves the quality factor to 14.000±1.000.

Abstract: The memory characteristics of Ni-NiOx core-shell nanocrystals (NCs) in the metal-oxide-semiconductor (MOS) capacitor structure were investigated. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) confirm the formation of the spherically shaped, well isolated, and uniformly distributed Ni NCs surrounded by NiOx (~1nm) in SiO2 gate oxide. The Ni-NiOx NCs embedded in SiO2 exhibited a large memory window of 9.8 V as well as efficient programming/erasing speed and improved retention characteristics of about 10 years. A possible band model needed for injection efficiency of carriers was given by considering the electron/hole barrier width and the additional interface states through the NiOx shell layer.

Abstract: Abstract: Color filter incorporating a subwavelength triangular-lattice cylinder arrays in metal-dielectric films on quartz substrate was proposed. The device consists of a quartz substrate, a triangular-lattice cylinder arrays in both dielectric layer of ZnS and a metallic layer of aluminum (Al). The broadband transmission characteristic of the proposed device in the visible wavelength range was investigated in detail by the rigorous coupled wave analysis (RCWA). Specially by discussing the effects of the structure parameters to the resonant wavelength, typical optimized structure parameters are obtained, in which more than 74.6% peak transmission efficiency with FWHM of ~ 80 nm were simultaneously achieved for the tricolor filters. The simulation results show that the peak transmission efficiency (PET) increases more than 17% with lower color cross-talk compared to the previous color filters.

Abstract: The present study has theoretically investigated the combined torsional buckling behavior of carbon nanotubes (CNTs) with consideration of scale effect in the multi-field coupling condition. The generalized governing equation of buckling for CNTs subjected to thermo-electro-mechanical loadings has been established based on an elastic shell model of continuum mechanics, in which scale effect is taken account of through the nonlocal elasticity theory. Except the applied torque and torsion-related axial load, the Van der Waals forces between adjacent nanotubes, as well as effects of temperature change and voltage load, is taken into consideration at the meantime. Numerical experiments are conducted to demonstrate the influences of different factors. The conclusions provided herein will be helpful and valuable for the dependent designs and related applications of CNT-based nano-structures serving in the complex thermal and electrical environment.

Abstract: MWNT –SiO2 composite film humidity sensors with different MWNTs proportions were fabricated and their performances under alternating current testing signals are investigated. Influence of MWNT content on humidity sensing characteristics of the sensors is explored and explained by vapor adsorption and capillary condensation effect. It is proved that 60% MWNT content sensors have humidity sensitivity of 1500% at 400 kHz testing frequency, much higher than those with other MWNT contents. In sensors’ sensitivity-frequency relation, maximum sensitivity comes from frequency section of 400kHz to 500kHz for sensors with higher MWNTs proportions.

Abstract: A new route to substitute for the traditional two-step method for adipic acid production has been investigated. Supported nano metal catalysts Au/C and Co/C were prepared and used for liquid phase oxidation of cyclohexane to adipic acid with oxygen as an oxidant. These catalysts were characterized by XRD, TEM and ICP-AES. The reactions were carried out in an autoclave with solvent and radical initiator at 373~423K and 1.5 MPa. Au/C (1.25%) was found to be a highly efficient catalyst for the oxidation of cyclohexane with a high conversion (44.93%) of cyclohexane and more than 54.85% selectivity to adipic acid. It is indicated that there was a potential application prospect for the nano-catalysts in one-step oxidation of cyclohexane to adipic acid.

Abstract: TiO₂ nanotube was synthesized successfully with different parameters via hydrothermal process, using nanopowder TiO₂ and concentrated NaOH solution as raw materials. If the hydrothermal temperature, hydrothermal time or washing conditions were changed, the structure of the nanotube was different. The phase compositions and morpholog ies of the TiO₂ nanotube was characterized by XRD and SEM. These results suggested that the length of the nanotube increased from 180 nm to 270 nm, and the diameter almost kept a fixed level about 15~20 nm within a range of 110°C~150°C. The length of the nanotube increased from 230 nm to 330 nm and diameter was nearly unchanged as the result of time increasing from 24 h to 48 h. Washing conditions were very important to influence the nanotube. When the deposit was washed directly with distilled water, short and thick nanorod were formated, and microrod generated with concentrated hydrochloric acid, and microrod structure with smooth surface was produced with absolute ethyl alcohol, and the nanotube was fabricated only after washing by dilute acid.

Abstract: Polyesteramide (PEA) have good mechanical properties, compositing with multi-walled carbon nanotubes (MWNTs) can further improve the mechanical properties of the polymer. In this paper, PEA/MWNTs were synthesized in-suit using the reinforcement of nanocomposite. SEM and tensile testing were used to characterize the composited polyesteramides. The results show that MWNTs can be uniformly dispersed in the composited polyesteramides, the PEA/MWNTs tensile strength and Elongation at break increased.

Abstract: Co-Ni alloy nano array was formed in applied magnetic field via liquid phase reduction method using different surfactants as soft templates.At last, The microstructure and the size of Co-Ni alloy nano-powder were illustrated with FESEM, and the powder’s composition was analyzed by XRD. In this experiment,the reaction temperature, the types and amounts of the surfactants,the mole ratio of the initial salt, in the alloy powder’s morphologies,were all studied.Finally, The powder’s magnetic property was tested by using VSM.