Applied Mechanics and Materials Vol. 492

Abstract: This paper present a new approach for fabricating 3D micro structures based on the elevated structures. The new fabrication method involves combinations of several basic techniques, but a key enabling techniques for the successful development of the fabrication process is combining the photolithography with e-beam lithography processes to create 3-D structures

Abstract: Cadmium sulfide (CdS) nanoparticles synthesized by utilization of wet chemical technique are grown in polyvinyl alcohol (PVA) matrix. X-ray diffraction (XRD) pattern shows the typical inter-planar spacing corresponding to the cubic phase of CdS. High-resolution transmission electron microscopy (HRTEM) studies show the nanoparticles formation with diameter around 11 nm. Particle size is further determined by dynamic light scattering (DLS) measurement. The polymerization of PVA is confirmed by fourier transform infrared (FTIR) spectroscopy of CdS nanoparticles. UV-visible optical spectroscopy study shows that sharp excitonic bands are largely blue shifted from the absorption onset of bulk CdS and inter band transition of copper doped samples. Thermal stability of the samples is measured by thermogravimetric (TG) analysis which is also studied in details.

Abstract: Using zinc chloride solution and ammonia (25%) as raw material, with the presence of surfactant (CTAB), the microrod ZnO material was synthesized by the hydrothermal method. The phase composition and microstructure of the prepared ZnO material were characterized with XRD and SEM. The results show that the ZnO material possesses a high degree of crystallization, its diameter below 4 μm, and its length about 35 μm. The gas sensing property of gas sensor fabricated with the prepared ZnO material was evaluated via the static volumetric method. At the operating temperature of 200°C, the gas sensor has high sensitivity and selectivity to CH₃COCH₃.The gas sensing characterization was also discussed.

Abstract: The use of photonic crystals (PCS) in biosensor applications has lead to the development of highly sensitive and selective microfluidic sensor elements. Two main advantages of these devices for sensing applications are their high sensitivity and their reduced size, which makes it possible, in one hand, to detect very small analytes without the need of markers (label-free detection), and to integrate many of these devices on a single chip to perform a multi-parameter detection on the other hand. In the present paper, we analyze the design of a highly sensitive microfluidic sensors based on 2D photonic crystal slab waveguide formed by increasing the radii of air holes localized at each side of the line defect and filling with homogenous de-ionized water (n_c =1.33). The transmission spectrum of the sensor has been obtained with the use of Finite Difference Time Domain (FDTD) method and it has been observed that a 306 nm wavelength position of the lower band edge shift was observed corresponding to a sensitivity of more than 927 nm per refractive index unit (RIU). Development of microfluidic sensor designs that enhance sensitivity is especially important because it allows detection of lower concentrations of analytes.

Abstract: In this paper, a compact modeling of lightly doped nanoscale Double Gate (DG) MOSFET transistor is presented. In the first time, a DG MOSFET transistor with long channel is considered. In this case, by using 1-D Poissons equation and applying the Gauss law at the interface of Silicone/Oxide, the static behavior of the long channel DG MOSFET can be observed by simple relationships between charges-voltages and charges-drain current. In second time, the dynamic behavior of the device is described through the intrinsic trans-capacitances. The present results (obtained using MATLAB) are validated by comparing them with those obtained using commercial software (Silvaco Atlas-TCAD).

Abstract: Metal-organic chemical vapor deposition (MOCVD) method has been applied to grow nanostructured ZnO films on Si (100) substrate at temperatures ranging from 200 to 550 °C. The as-prepared films were characterized by XRD, SEM, XPS analysis. The growth rate of ZnO films increases with increasing the deposition temperatures. The deposition temperatures have a drastic effect on the crystallinity and morphology of the nanostructured ZnO. Whisker shaped ZnO is formed at a temperature of 350 °C. The deposition time also affects the morphology of the particles. At 400 °C, sample with one hour deposition forms whisker shaped ZnO nanostructures whereas that of with two hours deposition forms flower-like nanostructures.

Abstract: In this paper, we present modeling of Heterojunction Bipolar Transistors (HBT) based on Si / SiGeC very high performance for telecommunications applications dedicated to radio frequency RF. The major objective of our work will be devoted to the influence of the germanium profile on the static and dynamic characteristics of the latter. The optimization of the profile of germanium in the base is a major element in the study of electrical characteristics of the HBT. This optimisation improves the static gain (β) of the transistor, while increasing the germanium profile in the base of 10% to 30%. However, the transition frequency (f_T), and the maximum oscillation frequency (f_max) decrease when the profile of germanium is greater than 20%. A numerical modelling approach is investigated using our 2D simulator SIBIDIF, which is based on the Drift-Diffusion Model (DDM). This method solves the continuity equations for electrons and holes and is coupled with the Poissons equation based on the concept of the finite difference mesh.

Abstract: A graphene/nylon-6 nanocomposite was fabricated by incorporating reduced graphene oxide onto a nylon-6 (N6) membrane via vacuum assisted self-assembly (VASA) method. The graphene oxide was synthesised through acid dissolution according to the method of Marcano & Tour and subsequently reduced to graphene using L-ascorbic acid. The surface morphology and electrical characteristic of graphene and its nanocomposites was characterized. The percolation threshold of the prepared nanocomposites was around 1.92% (w/w) with a sheet resistance of 3.839 x 10³ Ω per square (rsd= 0.22%, n=4). Different weight ratios of the nanocomposite were tested for its sensitivity towards the amine vapour. The final sensor for trimethylamine concentration has a working concentration range between 23 and 230 mg/L. The sensor exhibited linearity between 45 to 230 mg/L (r²= 0.9917) while the detection and quantitation limit was calculated at 0.39 mg/L and 1.30 mg/L, respectively. This nanocomposite demonstrates that it can be used as a chemiresistor gas sensor that is sensitive and selective to trimethylamine vapour.

Abstract: Nanometer-sized (Sr_xCa_1-x)₃Co₄O₉ powders were prepared using the sol-gel process. Two Ca-Co-O ceramic thermoelectric materials were then prepared and characterized with X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The microstructure and thermoelectric properties of the ceramic materials were studied. The experimental results showed that the crystals of (Sr_xCa_1-x)₃CO₄ grew into materials with high density and low pore rate under optimal Sr-doped conditions. The (Sr_xCa_1-x)₃Co₄O₉ ceramic materials contain directional arrays with cube-shaped grains in a layered arrangement. The crystals were fully developed and the interface between layers was clear-cut. The thermoelectric properties of (Sr_xCa_1-x)₃Co₄O₉ ceramics were greatly improved, with high Seebeck coefficient and high electrical conductivity. The Seebeck Coefficient positively correlated with the rise of temperature.

Abstract: We developed heterojunction-based Schottky solar cells consisting of π-conjugated polymers and n-type GaN. PEDOT: PSS was used as the transparent Schottky contact material. In order to improve the performance of solar cells, the effects of surface treatment on the electrical performance of PEDOT: PSS/n-GaN Schottky contacts were investigated. The Voc increased from 0.52V to 0.62V,0.54V and 0.54V and Isc from 0.33 mA/cm² to 0.45mA/cm²,0.40mA/cm² and 0.35mA/cm² after HCl, HF solution and oxygen plasma treatments. The I-V and the XPS measurements indicated that the barrier height of PEDOT:PSS/n-GaN was increased from 0.62eV to 0.76eV, 0.72eV and 0.70eV and the ideality factor improved from 1.81 to 1.63, 1.67 and 1.73 respectively, which induced the variation of the solar cells characteristics..