| Summary: | 碩士 === 國立彰化師範大學 === 光電科技研究所 === 101 === We demonstrated spin dependent transports in the ferromagnetic / normal-metal/ferromagnetic single-electron transistors (SETs) .The sample were fabricated on a thermally oxidized silicon substrate by standard e-beam lithography and shadow evaporation techniques. Transport measurements were conducted in a cryostat at a temperature of about 2K, which corresponds to an energy scale much lower than the charging energy of the SETs. The electrical measurements are divided into two parts. The first part is confirmed the existence of charging effect. The second part investigated the tunnel magnetoresistance of the magnetic SET between parallel and antiparallel state.
In type 1 devices (magnetic electrodes are the same size), as long as resistance more than one million ohms at 2K, the transport characteristics reveal single-electron charging effects, including the Coulomb staircase, Coulomb blockade, and Coulomb oscillations. The main emphasis is placed on the spin effects due to spin-dependent tunneling through the barriers, which gives rise to spin accumulation and tunnel magnetoresistance. Moreover, owing to different stationary spin accumulations in the parallel and antiparallel configurations, the conductance versus bias-voltage and gate-voltage (magneto-Coulomb oscillations) in the parallel configuration is also different from that in the antiparallel configuration. In type 2 devices (magnetic electrodes are different size), the experimental data shows the clear tunnel magnetoresistance behavior and nontrivial charging effect.
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