Solid State Phenomena Vols. 121-123

Abstract: A series of bulk and supported NiB amorphous alloy catalysts with different particle sizes were prepared by different chemical reduction methods. By adding a certain volume of NH3 to the reaction system and adjusting the reaction temperature, respectively, the velocity of the reaction between Ni2+ and BH4 - could be controlled and the NiB alloys with particle sizes ranging from 10 to 400nm were obtained. A novel method to prepare the supported NiB catalyst, the powder electroless plating method was also studied. The bulk and supported NiB catalysts were characterized by XRD, ICP and TEM. Hydrogenation of sulfolene was selected as the probe reaction to investigate their catalytic performance. The results revealed that the NiB/MgO prepared by Ag inducing electroless plating showed much higher catalytic activity than Raney Ni catalyst, and the powder electroless plating was a promising method to prepare the supported NiB amorphous alloy catalysts.

Abstract: Poly(vinyl alcohol) (PVA) nanofibers containing functional ZnS nanoparticles have been successfully prepared by electrospinning technique. The ZnS/PVA mixture solution for electrospinning was obtained by reacting Zn(Ac)2 with Na2S in the PVA aqueous solution. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses revealed that the morphology of the ZnS/PVA nanofibers consists of the dispersion of ZnS nanopaticles with cubic structure in PVA nanofibers. The coordinations between –OH and Zn2+ were characterized by infrared spectroscopy. The photoluminescence spectroscopy studies showed that the ZnS/PVA nanofibers had a strong blue-violet emission band at 450 nm, which may be associated with defect-related emission of the ZnS.

Abstract: It has been studied that the dependence of tunneling coefficient T on the ratio x of Ge, on the barrier width B L , on the well width W L and on the periodicity N in periodic superlattices Si1-xGex/Si by the method of transfer matrix, and shown in figures. The dependence of peak region width W on the above parameters are discussed in detail, and plotted, those are fitted in functions. These results may be useful to convert a weak mechanical signal into a strong tunneling current signal and to design electron devices based on meso- piezoresistive effect in the superlattices Si1-xGex/Si.

Abstract: We investigated the non-uniformity of the residual layer thickness caused by wafer deformation in an experiment that examined different wafer thicknesses using UV-NIL with an element-wise patterned stamp (EPS). Experiments using the EPS were performed on an EVG®620-NIL. Severe deformation of the wafer served as an obstacle to the spread of resin drops, which caused non-uniformity of the residual layer thickness. We also simulated the imprint process using a simplified model and finite element method to analyze the non-uniformity.

Abstract: Functional self-assembled structure with well-defined shapes and dimensions are of great current interest. Porphyrins are attractive building manifold patterning for these structures because of their electronic, optical, and catalytic properties. In this paper, we report a novel technique for the assembly patterning of polymers. An Electrospinning process was used to create patterning with diameter ranging from 3 μm to 4 μm and length of up to several hundred micrometers in the presence of Zinc Porphyrin. Scanning electron microscopy (SEM), UV- visible spectra and EDX spectra were used to characterize the patterning. The results indicated that the patterning depended on the concentration of Porphyrin and the operational conditions.

Abstract: In order to build a nano-device on polymer substrate, nano-size patterning must be done. However, conventional photolithography cannot be used to fabricate nano-sized patterns on polymer film due to the flexibility of polymer film and its potential interaction with developer solution and organic solvent. In this study, 100nm sized dense line and space patterns were made on flexible PET (polyethylene-terephthalate) substrate using newly developed monomer based imprinting lithography. Compared to hot embossing lithography, thermal curing imprint lithography uses monomer based imprint resin which consists of base monomer and thermal initiator. Since it is liquid phase and polymerization temperature is much lower than glass temperature of polymer, the nano-sized patterns can be transfer at much lower temperature and pressure. Hence, patterns as small as 100nm were successfully fabricated on flexible PET film substrate by monomer based thermal curing imprinting lithography at 85°C and 5atm.

Abstract: Flexible polyvinyl alcohol (PVA) templates with nano-sized patterns were fabricated by spin coating of PVA resin on silicon master wafer. Since PVA template has enough UV transparency, mechanical strength and thermal durability, it can be used as the template for UV-based and thermal nanoimprint lithography. The replicated patterns on the PVA template were transferred faithfully to the imprinted resin by imprinting lithography. As PVA template was dissolved in water, it was not necessary to deposit a releasing layer on the PVA template surface.

Abstract: A faithful pattern transferring onto a non-planar substrate was demonstrated by nano-imprinting technique. Uniform pressing of a flexible template onto a substrate was important for the faithful pattern transferring. Both the UV-based and thermal imprinting techniques were used to transfer patterns of 200nm sized features to the non-planar substrates such as outer wall of rod and inner surface of cylinder and it could be used for nano-devices such as lab on a chip.

Abstract: A first result of realization of silicon nitride templates on 100mm silicon wafer as nanoinprint mold using simple wet etching method is reported in this paper. The process is based on traditional photolithograph and following buffer HF wet etching, which started from a p-type wafer with 400nm thermal silicon oxide, 200nm PECVD silicon nitride and 400nm PECVD silicon oxide sandwich layer. After patterning with lithography, the patterned resist is used as mask for the isotropic underlayer wet etching of silicon dioxide with buffer HF solution. Using the obtained nanosacle silicon dioxide lines as RIE dry etching mask, silicon nitride template of 100nm width with steep sidewalls is successfully realized.

Abstract: The macroscopical breakage and nature change of material usually originate in nanometer scale, and the nature of some materials depends on temperature strongly. So it is extremely important for the research of heat transfer in micro-scale and nanometer technology to understand and control the influence of temperature on the nature of material, and developing advanced measuring technique can also improve our knowledge on theories involved in such problem. Due to the usage of variable-temperature sample stage, utilizable range of temperature is widely extended, and thus topography images of materials changing with temperature can be observed so that the thermal properties of materials can be studied further. Accordingly, the theoretical basis of heat-transfer and the influence of temperature on tunneling current owing to temperature variation should be presented. In the view of microscale heat-transfer, this paper describes the problem that heat current transfers from surface of sample to tip of probe through layer of air by means of Boltzmann theory, which can be expressed by the hyperbolic equation of heat conduction when the time is nearly equivalent to slack time and the scale is much larger than the characteristic scale of local thermodynamic equilibrium. The mode of heat-transfer on probe is also analyzed and the analytical solution is obtained in the paper. In addition, the influence of temperature increment of sample on tunneling current is discussed in detail and the change trend of tunneling current with temperature is also obtained in a limited temperature range. Due to such factors, which are possible to disturb the topography images of sample, there is no doubt that many difficulties will be brought to developing new technology such as detecting displacement and strain of materials at microscale by using the images of sample heated and unheated. To understand and control such factors has important advantage for making progress in the advanced scientific fields.