nanostructures

The concept of the transfer Hamiltonian formalism has been reconsidered and generalized to include the non-orthogonality between the electron states in an interacting region, e.g. quantum dot (QD), and the states in the conduction bands in the attached contacts. The electron correlations in the QD are described by means of a diagram technique for Hubbard operator Green functions for non-equilibrium states.It is shown that the non-orthogonality between the electrons states in the contacts and the QD is reflected in the ...

Magnetic thin films and patterned nanostructures have been studied with respect to their magnetic properties using SQUID-magnetometry, magnetic force microscopy, electrical measurements, and micromagnetic calculations.Properties of vortex domain walls, trapped in Permalloy nanowires with artificial constrictions, were investigated experimentally and by numerical calculations. In particular, the geometrical extent and strength of the pinning potential were evaluated. In these wires, long-range vortex domain wall displacement induced by spin polarized alternating currents was obtained numerically at reduced threshold current densities as compared ...

Fabricating nanostructures and tailoring their properties on the nanometer scales by conventional lithographic approaches are challenging. In particular, the creation of nanostructures with good alignment and uniform size, to enable and enhance desirable collective behaviors, is even more difficult. Such difficulties have compelled us to seek alternative approaches such as utilization of template methods to produce uniform nanostructures on the nanometer scale, and to form self-organized highly ordered arrays. Anodic aluminum oxide (AAO) template has a hexagonal array of pores ...

In this thesis we report on calculations for open quantum mechanical and certain microwave systems. The models refer to a quantum point contact and an electron cavity. We model this open system with an imaginary potential as source and drain, and use the finite difference method to make our calculations. We report on general features of the model we have found, and compare our calculations with measurements made on microwave cavities. Author: Hakanen, Jani Source: Linköping University Download This ...

One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices. Therefore, it is really important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nonawires, nanorods and quantum dots (QDs), and also investigate the structure and optical properties in detail by the methods of scan electron microscope(SEM), transmission electron microscope(TEM), resonant Raman, photoluminescence(PL) and ...

We study an unusual transition between two different types of self-assembled structures in aqueous solutions. Mixtures of a cationic surfactant, CTAB and the organic compound, 5-methyl salicylic acid (5mS) spontaneously self-assemble into unilamellar vesicles at room temperature. Upon heating, these vesicles undergo a thermoreversible transition to "wormlike" micelles, i.e., long, flexible micellar chains. This phase transition results in a 1000-fold increase in the solution viscosity with increasing temperature. Small-angle neutron scattering (SANS) measurements show that the phase transition from vesicles ...

The need for improved measurement technology for the detection and monitoring of gases has increased tremendously for maintenance of domestic and industrial health and safety, environmental surveys, national security, food-processing, medical diagnostics and various other industrial applications. Among the several varieties of gas sensors available in the market, solid-state sensors are the most popular owing to their excellent sensitivity, ruggedness, versatility and low cost. Semiconducting metal oxides such as tin oxide (SnO2), zinc oxide (ZnO), and tungsten oxide (WO3) are ...