Min Ren

Spin-polarized thermionic emission at the interface of ferromagnetic metal and organic semiconductor

We present a model to explain the spin-polarized injection from ferromagnetic metal into organic semiconductor. Thermionic emission mechanism is considered as the dominant transport mechanism at the interface at low bias. Boundary condition is determined from the relationship of the spin-dependent quasi-electrochemical potentials across the interface. The dependences of the current spin polarization on the control parameters, which include the Schottky barrier height at the interface, the spontaneous spin polarization in ferromagnetic metal, and the bias, are demonstrated.

A novel boundary approach for spin polarized transport in pseudo-spin-valve structure

The interfacial effect on spin polarization is studied in a pseudo-spin-valve structure (PSVs) consisting of two ferromagnetic layers (FM) separated by a nonmagnetic metallic layer (NM). We adopt the macroscopic two-current drift-diffusion model and boundary conditions taking spin flip at FM/NM interfaces into account. The two FM/NM interfaces with respect to the spacer NM layer are combined into a single interface under some appropriate assumptions and new formulae for spin transport boundary conditions are derived. The analytical solutions of spin polarization for both side interfaces of the free layer are calculated from those boundary conditions.

The Impact of the External Magnetic Field on the Resistance-Current Curve of the Deep Submicron Pseudo-Spin-Valve Structure

The current induced magnetization switching effect in a deep submicron pseudo-spin-valve (PSV) at low external magnetic field (EMF) is theoretically studied. Both the spin-dependent scattering at the interfaces and the relaxation of spin accumulation in the ferromagnetic layer is considered within a macroscopic phenomenological model based on the magnetic dynamic equation. Magnetization switching conditions and then the resistance-current curve of the PSV structure are calculated at different EMF. It is demonstrated that the hysteresis loop in the resistance-current curve shifts with the change of the EMF. All the simulation results are consistent with the experiments reported.

Spin-polarized injection through the n-magnetic/p-nonmagnetic semiconductor heterojunction

In this paper, the spin-polarized injection through n-magnetic/p-nonmagnetic semiconductor heterojunction was investigated theoretically. Based on the drift-diffusion theory and continuity equation, a model was established to explain the spin-polarized injection through the magnetic heterojunction. Boundary conditions were determined by analyzing the relations of the quasi-chemical potentials in n and p regions. The distributions of the charge density, spin density and spin-polarization were calculated using this model. The results demonstrate that an effective spin-polarized electric injection through the heterojunction may be achieved without external spin injection or the application of a large bias. The factors affecting the nonequilibrium spin-polarization (NESP) in the nonmagnetic region were also given based on the simulation results

Study of electron transfer in metal-alkanethiol SAM-metal junctions

As the basis of molecular electronic devices, more attentions have been concentrated on the electron transfer in single-molecule junctions. In present paper, molecular junctions were constructed by using a sandwich structure that consists of metal film/self-assembled monolayers (SAM)/Au coated conducting-probe atomic force microscopy (CP-AFM) tip. The dependence of I-V characteristics on the length of molecules was investigated to explain electron transfer process in saturated molecules such as alkanethiol monolayer. The experiment results show that the molecular conductance decreases with increasing of molecule chain length was found in the sandwich structure

Rectification Characteristics in Saturated Molecular Junction

One of the molecular systems that has been studied extensively is saturated molecules, such as alkanethiol CH3(CH2) n-1-SH. In present paper, molecular junctions were constructed by using a sandwich structure that consists of metal electrode/self-assembled monolayers (SAM)/Au coated conducting-probe atomic force microscopy (CP-AFM) tip. The dependence of I-V characteristics on the length of molecules was investigated to explain electron transfer process in saturated molecules. Tunneling was confirmed as the dominant mechanism. Rectification effect was demonstrated in the sandwich structure, and possible explanation based on the tunneling model was proposed