Modeling the Injection of Spin-Polarized Electrons into a Semiconductor

Dr. Yuriy Pershyn, of Professor Privman's group, is modeling the process of injection of spin-polarized electrons into a semiconductor in terms of the drift-diffusion model. The system under investigation is shown in Figure 1. He calculated the spatial distribution of the electron spin polarization and found that it can be enhanced at the boundary between two different semiconductors.

Figure 1. Spin-Polarized Electron Injection System

Spintronics: Device Simulation for Spin Polarized Transport

Spintronics is one possible course of development for modern electronics. See Figures 2 and 3. It is supposed to manipulate current spin-polarization, which will give an additional degree of freedom for information carriers. Moreover, electron spin possesses quantum properties, which can be used for quantum information processing.

Figure 3. Model of a 2D Structure

Dr. Semion Saykin, of Professor Privman's group, and graduate student Min Shen, of CAMP Professor Ming-Cheng Cheng's group, are investigating the influence of spin-orbit interaction on the electron transport. Spin-orbit interaction provides possible control for spin polarized current (for example, Datta and Das transistor). Also it can create a strong spin dephasing mechanism even at the absence of magnetic impurities. Defects of crystal structure, impurities, and phonons influence the electron spin polarization and reduce the efficiency of spintronics devices.

They treat spin quantum-mechanically, using the density matrix (polarization vector) description, while treating spatial motion semi-classically in Monte Carlo simulation to study the electron transport and evolution of spin polarization in the InGaAs/InAlAs quantum well. See Figure 4. This model can be applied for simulation of steady state for dynamic regimes of spintronics devices.

Figure 4. Evaluation of electron spin polarization

Numerical Modeling of Non-Linear Physical Phenomena

Dr. Vyacheslav Gorshkov, Professor at the Institute of Physics in the Ukraine and a member of Professor Privman's group, is an expert in numerical modeling of non-linear physical phenomena in different branches of science. In particular, he developed a mathematical model to understand the physical nature of microwave radiation in electron-hole plasma inside the semiconductors within strongly crossed magnetic and electric fields.

Dr. Gorshkov has used numerical experiments to study the processes of micro-drop generation in liquid metal sources of ions, which are used in the microelectronic industry for the covering of different materials used in space shuttle engines of low torque (for accurate orientation of space objects). He has done a considerable amount of work in the numerical modeling of different work regimes of powerful CO2-lasers on induced discharge and of excimer lasers with mixed inert gases. He is collaborating with the Lawrence Berkeley National Laboratory in the U.S. to develop mathematical models for non-linear processes in plasma lenses for the focusing of highly accurate beams of heavy ions. Also he is studying the growth and aggregation dynamics of nanosize particles in highly concentrated solutions, and collaborating with the U.S. Air-Force in studying the properties of optical vortexes in singular wave packets.

Theoretical Models to Explain Formation Mechanisms of Monodispersed Particles

In addition to his quantum physics work, Professor Privman and his group are collaborating with CAMP Professors Egon Matijevic', Michal Borkovec, and Dan Goia on a project to develop a better understanding of the formation of uniform nanosize and colloidal particles. This knowledge is essential in numerous areas of modern technology and medicine, because many properties of materials (such as optical, magnetic and catalytic) are strongly dependent on the particle size and shape. Thus in order to produce materials of predictable and reproducible properties, it is essential to develop techniques for the preparation of monodispersed particles and to devise theoretical models to explain the mechanisms of their formation. Documented evidence shows that a majority of uniform colloids are formed by aggregation of smaller, nanosized subunits.

This group of researchers experimentally studied the aggregation process of nanosize precursors for three representative systems (CdS, Au, Fe2O3). They identified parameters that control the size distribution and internal structure. They also developed and implemented a theoretical model predicting the size selection. The model calculations matched the experimental results.

For more information about Professor Privman and his research, you may call him at 315-268-3891 or send email to privman@clarkson.edu.