Solid State Phenomena Vols. 121-123

Abstract: A simple and cheap method has been applied to synthesize single-crystal uniform ZnO tubes with high yield in a hydrothermal process using Zn(NO3)2⋅6H2O and methenamine as reaction precursors at low temperature. The products are characterized by XRD, SEM, TEM and SAED. ZnO tubes are uniform single-crystal structures and grow along the [0001] direction. They have straight and regular hexagonal configuration with faceted ends and slippery side surfaces. The growth mechanism of ZnO tubes is investigated and the processing conditions are critical for the formation of ZnO tubes.

Abstract: Monodisperse wurtzite ZnO nanorods with the length of 4 μm and the diameter of 200 nm were prepared via a simple solution chemical process. The crystal phases and the microstructure of nanorods were studied via XRD, SEM, respectively. The properties of the excitonic luminescence are investigated by using the laser power dependence and temperature dependence of photoluminescence (PL) spectra.

Abstract: In this research, nanoscale spatial resolution p-n junction photodetector arrays were developed using ZnO nanorod arrays grown on p-type silicon substrates. In order to optimize the nanorod array quality, an advanced combinatorial spreadsheet approach was used to optimize the Au catalyst thickness. The crystallinity of these as-grown ZnO nanorods’ was compared to that of bulk and thin film ZnO materials.

Abstract: In this paper, field emission from ZnO was studied by morphological and electronic design. By fabricating ZnO into nanopin structure with sharp tip, we can obtain low threshold and high emission current density. By doping ZnO with gallium, we can lift up the Fermi level and increase the conductivity to enhance the field emission. The fabrication of nanostructures and analysis of field emission will be discussed.

Abstract: In this paper, we will present theory for nDSE (nano-scale Displacement Sensing and Estimation) and its application framework: IDMA (Indirect Displacement-Measurement-based Alignment). nDSE presents a clear and novel theoretical explanation to displacement sensing and estimation, especially down to the nano scale, a precision traditionally thought difficult or impossible to achieve because the displacements are below the wavelength of light and smaller than the pixel dimensions of practical observation systems. IDMA is an enabling framework based on nDSE to provide a new, low-cost, high precision overlay alignment for the challenging issue of nano scale alignment and metrology.

Abstract: With the progress of instrumentation in nanoscale visualization, tremendous sicentific dicoveries and understanding has been made. A great breakthrough in nanotechnology came with the inventions of scanning tunneling microscope in 1982 and atomic force microscope in 1986. These revolutionary inventions opened the nanoworld to scientists and engineers by visualizing it with atomic resolution. However, the lack of efficient nanomanipulation capability has become a bottleneck for creating devices using nanocomponents both in the research community and industry. This paper presents the stateof- the-art of nanomanipulation concepts, manipulator designs, manipulator systems. Such an approach has certain advantages over existing designs which have such limitations as device sizes orders of magnitude too large for in situ applications and further device miniaturization restricted due to the adverse effect of physical scaling laws.

Abstract: The atomic force microscope (AFM) obtains its topographical information from the short-ranged repulsion resulting from the overlap of electronic shells between tip and hard samples. However, scanning soft samples such as surfactants or biological material within liquid media leads to a very different scenario due to the long-ranged double layer interactions and the specific tip penetration through the scanned layers. We show that AFM images and force vs. distance curves can be used to obtain relevant information on formation, characteristics and behavior of soft self-assembled nanostructures of surfactants, phospholipids and of cells under physiological conditions.

Abstract: At the (110) cleaved surfaces of p-type GaAs with degenerate doping level, the negative differential resistance (NDR) inside of the band gap was observed in scanning tunneling spectra (STS) measurement. The origin of the NDR was found to be the voltage dependence of the transmission coefficient through the double tunneling barrier, a phenomenon similar to that reported by Esaki and Stiles in planar metal-insulator-semiconductor tunnel junctions.

Abstract: Electrochemical processing is a cost effective and low-temperature approach suitable for the fabrication of certain unique nanostructures that are difficult to obtain by other methods. Here we report on the synthesis of nanowires and nanoporous structures with the intention to control the magnetic properties of conventional materials. Nanowires with variable sizes (diameter 15 nm - microns, and length up to 100 microns) have been fabricated by template assisted electrodeposition. Utilizing a combined alloy electrodeposition and electrochemical dealloying approach, porous nanostructures with controlled pore size and porosity have also been synthesized. Magnetization, Curie temperature, coercivity, saturation field, and remnant magnetization of these magnetic nanostructures exhibit much wider tunibility compared to bulk and thin film samples.

Abstract: Thermal analysis and Raman spectra were carried out in SrBi2Ta2O9 (SBT) nanoparticles to investigate phase transitions. Two anomalies have been observed in temperature dependence of specific heat for SBT nanoparticles. Under the combination with Raman spectra, it indicates that there exists a new ferroelectric intermediate phase in the phase-transition sequence. So we can conclude that the phase-transition sequence in SBT nanoparticles should be ferroelectric-ferroelectric-paraelectric. Moreover, the size effect was discussed in consideration of inner compressive stress in nanoparticles for this special transition behavior. The calculated results show that the SBT nanoparticles keep the ferroelectricity until the particle size is decreased to 4.2 nm.