Electrical transport in nanoscale hybrid structures

We report the experimental studies on the electrical properties of boron nanowires and the spin dependent transport in ferromagnetic single electron transistors.; Crystalline boron nanowires have been synthesized by catalyst chemical vapor deposition method. The diameter of the nanowires ranges from ∼20 nm to ∼200 nm, with length up to several tens of microns. The electrical transport study shows the synthesized nanowires are p-type semiconductors. The nanowires form ohmic contact with Ni and Schottky contacts with Cr, and Ti. The conductivity and mobility of the nanowires are calculated to be in the range of 10-3 to 10-2 (Ocm) -1, and 10-3 cm2/Vs, respectively. Schottky diode based on the above discoveries has been fabricated.; Single electron transistor has two metal leads coupled to an island through very small capacitance and large resistance. It is the most sensitive devices for charge detection. A double dose exposure process is developed to get a narrow top line and a large undercut in electron beam lithography system whose accelerating voltage is 100 kV. Spin dependent transport study on ferromagnetic single electron transistor with high resistance (50 MO) shows that the resistance increases when the two ferromagnetic leads switch from parallel to anti-parallel magnetization alignment. However, for the same bias polarity, the devices with relative low resistance (<5 MO) show a resistance decreases when the two ferromagnetic leads are in anti-parallel alignment. Theoretical analysis shows that the resistance increase in high resistance device is due to the Meservey-Tedrow effect. Resistance decrease in devices with relatively low resistance is due to the superconducting gap suppression caused by spin accumulation in the Al island.; A single electron spin filter is proposed in the conclusion part of this report.