Abstract: In this paper, analytical modelling and performance analysis of novel device structures such as single gate SOI Tunnel Field Effect transistor (SG SOI TFET), Dual-Material Gate TFET (DMG TFET) and Dual Material Double Gate TFET (DMDG TFET) are proposed. The performance of the three devices is studied and compared in terms of surface potential, electric field and drain current. The DMDG TFET shows better performance in suppressing leakage current and enhancing ION current than the SG SOI TFET and DMG TFET. The analytical models of the devices are found to be in good agreement with the results obtained using two-dimensional TCAD device simulator.
Abstract: The deposition of a compact amorphous silicon/nano-crystalline silicon material is demonstrated by hot-wire chemical vapour deposition using a sequential hydrogen profiling technique at low hydrogen dilutions. Nano-crystallite nucleation occurs at the substrate interface that develops into a uniform, porous crystalline structure as the growth progresses. A further reduction in the H-dilution results in the onset of a dense amorphous silicon layer. The average crystalline volume fraction and nano-crystallite size in the sample bulk amounts to 30% and 6 nm, respectively, as probed by Raman spectroscopy using the 647 nm excitation. The change in hydrogen dilution is accompanied by a graded hydrogen concentration depth-profile, where the hydrogen concentration decreases as the growth progresses. The level of post-deposition oxidation is considerably reduced, as inferred from infrared spectroscopy. The presence of oxygen is mainly confined to the substrate interface as a result of thermal oxidation during thin film growth.
Abstract: In this study, electrospun nanofibers of polyurethane were prepared utilizing a new solvent system made of chloroform/methanol. Also, we planned to assess effects of four important parameters on diameter of electrospun polyurethane nanofibers using Artificial Neural Networks (ANNs). The parameters investigated included flow rate of syringe pump, distance of spinneret to collector, applied voltage and concentration of polymer solution. Diameter of obtained electrospun nanofibers was measured using scanning electron microscopy (SEM). Results showed that flow rate and distance had reverse relation with fiber diameter, while applied voltage and concentration of polymer solution directly affected the diameter. Also, polymer concentration was shown to be the dominant factor here.
Abstract: Magnetite nanoparticle with average size 7-10 nm was embedded with biocompatible polyvinyl alcohol nanofiber and the average diameter of nanofiber is 115 nm. The nanofiber was further assembled over polymeric mesh to analyse the release mechanism of nanoparticles from polymer nanofiber. A hydrodynamics setup was constructed to study this system. Prior to hydrodynamics the nanofiber was allowed to react with water in static mode and observed that the magnetite nanoparticles were released from the nanofiber with increase in time. UV-Visible Spectrophotometer is used for analysis of absorbance and transmittance of polyvinyl alcohol-magnetite nanoparticles solution, nanofiber and films. High-resolution scanning electron microscopy is used to analyze the dimension of nanofiber; High-resolution transmission electron microscopy is used to find the size of magnetite nanoparticles. Here, an online spectroscopic technique was used to study the release mechanism of nanoparticles from nanofibers samples of different layers during hydrodynamics. The results reveal that the quantity of magnetite nanoparticles can be controlled by embedding into nanofibers during hydrodynamics. Also, the spectroscopic results indicate the quantity of nanoparticles released from nanofiber. This mechanism can be utilized to control the required quantity of nanoparticles to release at particular location through a polymer mesh assembly.
Abstract: Thin UV-blocking films of poly(methyl methacrylate) and CdSe quantum dots (QDs) (CdSe@PMMA) are built up by CdSe-azo initiator through surface-initiated free-radical polymerization. CdSe@PMMA nanocomposite film possesses excellent transparency and ultraviolet (UV)-shielding properties. The average size of CdSe QDs is found to be less than 5 nm and well dispersed in the PMMA matrices without any significant agglomeration by the transmission electron microscopy (TEM) measurement. At the same time, excellent fluorescence (FL) spectra of the nanocomposite indicate that the luminescent properties of CdSe QDs remain effective after the polymerization. Such the transparent and luminescence CdSe@PMMA nanocomposite film exhibits prominent UV-absorbing capability and the high optical transparency in the visible-wavelength region, thus make it to be a promising material for the large scale fabrication of diverse optical devices.
Abstract: We have developed an aerosol-based technique for deposition of monodisperse ensembles of spherical SiO2 nanoparticles on the surface of single-crystal silicon substrate (1 cm2) with an average surface particle density of about 2.1±0.4 particles per μm2. The obtained samples of monodisperse ensembles SiO2 nanoparticles was characterized by scanning and transmission electron microscopy. The ensemble of deposited nanoparticles is characterized by a narrow size distribution with a modal size of 26.6 nm and a full width at half maximum of 3.5 nm according to the atomic force microscopy data. We have demonstrated the use of the obtained test structure to determine the effective radius of the tip of an atomic force microscope.
Abstract: Well-defined functional block copolymers, polybutyl methacrylate-b-polyglycidyl methacrylate (PBMA-b-PGMA), were successfully synthesized via initiators for continuous activator regeneration atom transfer radical polymerization ( ICAR ATRP) with pentamethyldiethylene-triamine (PMDETA) as a ligand and copper bromide (CuBr2 ) as a catalyst with concentration of 500 ppm. The PBMA-b-PGMA grafted with titanium dioxide (TiO2 ) nanoparticles was obtained through the reaction between the epoxide on the PGMA segment and amine group on the surface of modified TiO2 nanoparticles. Results showed that the PBMA-b-PGMA block copolymer with about same length of PBMA and PGMA segment could get highest graft ratio and about 17%wt TiO2 nanoparticles were successfully grafted onto the PBMA-b-PGMA block copolymer. The sizes of the PBMA-b-PGMA grafted nanoparticles were about 74 nm in ethyl acetate. The PBMA-b-PGMA grafted TiO2 nanoparticles showed very good dispensability in organic solvent (e.g. ethyl acetate) and polymer matrix. Polymethyl methacrylate (PMMA) containing 0.5%wt PBMA-b-PGMA grafted TiO2 nanoparticles showed strong absorption at about 300 nm and good transparency in visible region, which was attributed to good dispensability of PBMA-b-PGMA grafted TiO2 nanoparticles in PMMA matrix.
Abstract: Nanocrystalline Al2O3 powder has been successfully synthesized by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders was investigated through X-ray diffraction in terms of their crystallinity and crystallite size. Subsequently, a detailed transmission electron microscopy (TEM) investigation, including specific area electron diffraction (SAED) analysis revealed the crystallographic alterations and morphological information even at lattice scale which co-include the XRD analysis. The results obtained allow to explain the evolution of an amorphous state into different crystalline phases with increased calcining temperature; and their relation to particle size. The particle size is found to be closely related to phase transition of Al2O3 from γ → δ → θ → κ →α. The existence of distinctive bonds and band energy were studied by employing Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy, respectively. On the other hand, thermo gravimetric analysis (TGA) had also been performed to confirm the phase purity of nano powder.
Abstract: Cr layer was fabricated on 40Cr steel by electric brush plating process and then treated by high current pulsed electron beam irradiation technique. Surface microstructures of specimens before and after the irradiation were investigated. Results show that Cr surface is composed of uniformly distributed small nodule units which are composed of fine Cr particles smaller than 100nm. After high current pulsed electron beam treatment, many cracks are found on surface. The main reason is possibly due to the quasi-static thermal stresses accumulated along the surface of the specimens during the electron beam treatment. The surface grain grow from Cr particles because of heating by electron beam, and their size is less than 200nm.
Abstract: Hydrolyzing the cellulose amorphous regions with high selectivity while protecting the crystallite phases unaltered during acid hydrolysis is still a great challenge in nanocellulose industry. Due to this reason, transition metal based catalysts such as Fe (NO3)3-, Co (NO3)2- and Ni (NO3)2metal salts were chosen as promoter to co-catalyze with H2SO4 in order to develop a facile hydrolysis technique for the preparation of cellulose crystallites inform nanodimension from native cellulose source. This study investigated the hydrolysis efficiency of three different transition metals (Fe3+, Co2+ and Ni2+) on cellulose crystallinity index, structure and morphology of the products.Results showed that the transition metal salts (Ni2+, Co2+ and Fe3+) were capable to selectively degraded cellulose amorphous structure with increase of crystallite sizes (8.12-27.8 nm) and improved of crystallinity index (65.5-70.3 %), as compared to native cellulose. Furthermore, surface morphology study indicated the cellulose fibers were successfully disintegrated into smaller fragments (diameter ranges of 18.5-31.5 nm) with spider-web-like nanostructured surfaces. Higher oxidation state of Fe (III)-cation with trivalent state rendered more effective hydrolysis effect in preparing the cellulose crystallites as compared to divalent state of Co (II)- and Ni (II)-cations.