For decades, electronic devices have been relying on the transport of electronic charge. The electron spin degree of freedom, however, was often ignored. A new technology called spin electronics (Spintronics) has emerged since the discovery of giant magnetoresistance (GMR) effect in 1988. Today, GMR read head has become the key for high-density magnetic information storage. At the same time, much progress has been made in making magnetic random access memory (MRAM) based on the tunneling magnetoresistance (TMR) effect. The ability to manipulate electron spin states is critical to extremely high-density information storage, electron-spin-based quantum computing, magneto-electronic sensors, and perhaps future spin electronic devices and systems yet to be imagined. As the trend of device miniaturization continues, such applications require a good understanding of the fundamental physics of spin dependent transport in nanoscale structures.

The proposed project is to combine the recent developments in spin tunnel junctions and single electron transistors, to fabricate and characterize nanoscale hybrid junction structures that reveal new physical aspects of quantum states and dynamic behavior of single electron spins. Several interesting effects have been predicted for spin-dependent transport in ferromagnet (FM)/metal/FM and FM/superconductor/FM single electron transistors. The project is aimed to experimentally verify these theoretical predictions. The approach of this study is to fabricate hybrid junction devices using ebeam lithography and shadow evaporation techniques. This work contributes to the current research in spintronics community and provides more comprehensive understanding of the spin dynamics in order to develop innovative spin based nanoelectronic devices.

Anodic titanium oxide nanotubes film has been synthesized by two-step anodization. The conductivity at the crystallized barrier layer can be improved by NH4Cl treatment, which facilitates the high filling rate electrodeposition. Three dimensional Cu2O/TiO2 p-n junction arrays are then constructed by electrodepositing Cu2O into TiO2 nanotube matrix. The improved photovoltaic performances benefits from the high junction interface as well as the quasi-one-dimensional carriers’ pathway due to the radial hetero-junction nature. The versatile process can be used to fill various metal or semiconductor for functional applications.

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Highly conducting and porous carbon nanotubes are widely used as electrode in double-layer-effect supercapacitors. In this presentation, vertical TiO2 nanotube arrays are fabricated by anodization process and used as supercapacitor electrode utilizing its compact density, high surface area and porous structure. By spin coating carbon nanotube networks on vertical TiO2 nanotube arrays as electrodes with 1M H2SO4  electrolyte in between, the specific capacitance can be enhanced by about 30% compared to using pure carbon nanotube network alone because of the combination of double layer effect and redox reaction from metal oxide materials. With cyclic voltammetry (CV) and galvanostatic (GV) charge-discharge measurements, this type of hybrid electrode has proven to be suitable for high performance supercapacitor application. The electrochemical impedance spectroscopy technique shows that the device has good capacitive behavior and electrical conductivity. This approach is also a potential application for flexible electronics.