Advanced Materials Research Vol. 684

Abstract: For resistive random access memory (RRAM), there is an important issue about variations of switching characteristics such as set/reset voltage of resistance state. The variations may result in an incorrect reading operation. Another issue is device yield, which determine whether fabricated memory can be applied in commercial product. We investigated the switching performance of HfOx metal oxide as a resistive switching layer embedded with and without Pd metal nanocrystals. Compared with Pd/HfOx/TiN structure, the memory embedded with Pd metal nanocrystals (Pd/Pd embedded HfOx/TiN) shows high yield, better electrical uniformity and reliability for the flexible electronics application.

Abstract: The sensor behavior of nanostructured doped silica films produced by sol-gel way were examined. Hygroscopic substances and polyoxometalates were used as additives to make more significant sensitive characteristics of initial matrix. Factors that have effect on sol preparation and films forming were investigated. Adsorption activity of the sensitive films was studied and it was shown that the films had a highly developed surface with nano-size pores. Change of initial conditions of sol-gel process gives opportunity to influence on kinetics of gel formation and consequently, on structure and properties of final materials. The study showed that the conditions of the environment affected the sensors characteristics markedly, which can be improved by choosing of the right procedure of forming and treatment. Influence of type and additive substances quantity into doped films was discussed in the paper

Abstract: The aim of the study was to enhance the stability of 6-gingerol, a major constituent in ginger extract, using nanoemulsion formulations. The effects of extraction techniques and solvents on the content of 6-gingerol in ginger powders were investigated. Assessments of three commonly used extraction techniques (maceration, sonication and soxhlet extraction) with two different extraction solvents (methanol and acetone) were used in this study. The highest of 6-gingerol content was obtained by using soxhlet extraction with acetone. Nanoemulsions were prepared from a mixture of oil phase (coconut oil and squalene), Cremophor® ELP, acetone and ginger extract by spontaneous emulsification method. Effect of coconut oil and squalene mass ratio on nanoemulsion formations were evaluated for the further optimization of the system, which characterized by droplet size, polydispersity index (PI), zeta potential and Oswald ripening. Stability studies at 4°C and ambient temperature for 3 months were performed. The formulation containing the mass of coconut oil to squalene ratio of 0.8:0.2 was stable and had the required droplet size (122.2+2.2 nm) in relation with PI of 0.18+0.07, zeta potential of -20.8+0.4 mV and Ostwald ripening of 0.11 nm.day-1. Negative-staining transmission electron microscopy (TEM) was used to image the emulsion droplets. Stability test under heating-cooling cycle also performed on optimized nanoemulsion. Then, the sample was analysed for 6-gingerol content. The percentage of the remaining 6-gingerol of optimized nanoemulsion was 90.89. Hence, it was concluded that the stability of 6-gingerol could be enhanced by using nanoemulsion formulation.

Abstract: We demonstrate experimentally the enhanced performance of the plasmonic silicon solar cell by using a nano-sized indium-particles and different thickness of TiO2 space layer structure. The optical reflectance, dark and photo current-voltage, and external quantum efficiency are measured and compared at each stages of processing. The conversion efficiencies enhancing of 17.78%, 27.5% and of 47.85% are obtained as the solar cell with indium nanoparticles on a 10-nm, a 30-nm and a 59.5-nm thick TiO2 space layer, respectively, compared to the solar cell without coated a TiO2 layer. Furthermore, the plasmonics conversion efficiency depend on the thickness of space layer are also demonstrated that the increasing by 15.46%, 12.1% and 6.08% for the solar cells with a 10-nm, 30-nm and 59.5-nm thick TiO2 space layer, respectively, were obtained.

Abstract: Two-dimensional ZnO nanowalls were rapidly grown on glass substrate by thermal evaporation at low temperature without any catalysts or the pre-deposition of a ZnO seed layer on the substrate. Most of the ZnO nanowalls grown at 450°C were vertical on substrate and they were about 70-200 nm thick and 2 µm long. The room-temperature photoluminescence (PL) spectra showed a strong intrinsic ultraviolet (UV) emission and a weak defect-related emission. Hydrogen-sensing characteristics of the ZnO nanowalls have been investigated, and that make them become attractive candidates for gas sensor.

Abstract: This paper shows how much the size of groove and ridge, which were fabricated on the silicon wafer, affected on the hydrophobicity of the grooved surface without chemical treatments and with chemical treatment such as self-assembled monolayers (SAMs) of organic silane. Furthermore, the contact angles (CAs) of water droplet on specimens were measured and compared with theoretical CAs of droplet in Cassie-Baxter state. The experimental results indicated that the specimen with the extensive groove width had super-hydrophobicity as compared to the specimen with relatively narrow groove width. The highest CAs of chemically non-treated specimens and chemically treated specimens were 171.9˚ and 173.1˚. This work explains that the grooved surface with nano-ridges and SAM coating contributes to improve hydrophobicity of surface.

Abstract: Submicron rod-like ZnO was prepared by hydrothermal synthesis on the Si substrate which was prepared with ZnO seed layer by ultrasonic spray pyrolysis. The X-ray diffraction (XRD) pattern indicates that the as-grown ZnO is elongated uniformly along the c-axis and is hexagonal wurtzite structured; the scanning electron microscopy (SEM) results show that the diameter of the as-grown ZnO is 288nm and the uniform height is 3.78μm, so the aspect ratio is about 13; the atomic force microscope (AFM) results show that the fluctuation of the sample’s surface is even; the photo-luminescence(PL) spectra demonstrated that the sample has a single emission at 388nm, indicated the nanostructure has little dot defects.

Abstract: This paper studies the deposition process and mechanical properties of Cu thin films deposited on single crystal copper substrates with various surface roughnesses by molecular dynamics (MD). In the effect of vacancy concentration (Cv) of substrate, the Young's modulus of sample decreased as the Cv of substrate increased but the adhesion force will increase as the Cv of substrate increases. The effect of substrate roughness on the peak intensity of crystal orientation has little. And the greater Cv of substrate, the surface roughness of the deposited thin film also increased. In the effect of numbers of deposited atoms, the deposited thin film thickness increases, the surface will be relatively flat and the Young's modulus will also increase. By the XRD pattern, the principal growth directions of thin film are the (220) and (200) in the early stage of growth during deposition. However, with the thickness increasing, the (111) will be the preferred orientation.

Abstract: According to recent references, the progress on cytotoxicity in vitro of carbon nanotubes (CNTs) including the factors such as size , residual metal catalysts,and detection methods influencing cytotoxicity of CNTs are summarized. The results shown that residual metal catalysts must be removed as much as possible and ensure CNTs in some concentration range before using them.Biocompatibility of CNTs must be considered and chemical modification of CNTs to improve their use safety and advantages is indispensable.