 |
|
Biography
Joydeep Ghosh was born in Kolkata, India. He studied electrical engineering at the Jadavpur University, Kolkata. He was in IBM India Pvt. Ltd. for almost 3 years. Then he studied masters in "Micro and Nano Science" at the Technical University of Chemnitz, Germany, where he completed his studies in 2011. He joined the Institute for Microelectronics in March 2012. His current scientific interests include the spin injection and transport model in silicon.
Silicon and Spintronic Devices
Silicon, the main material of microelectronics, is now gaining momentum for use in electronic applications involving spin. It is a perfect material for spin-driven applications due to the weak strength of the spin-orbit interaction in the conduction band and is predominantly composed of non-magnetic atoms, which results in a long electron spin diffusion length even at room temperature.
On the other hand, the electron spin possesses several exciting properties suitable for future devices. It is characterized by only two projections on a chosen axis, up-spin or down-spin, and it can change its orientation rapidly by utilizing an amazingly small amount of energy. Employing spin as an additional degree of freedom is promising for boosting the efficiency of future low-power nanoelectronic devices, with high potential for both memory and logic applications.
The spin injected in silicon is not conserved and relaxes to the zero equilibrium value while diffusing. The electron spin lifetime is determined by the intervalley spin-flip processes. We have utilized a k·p approach well-suited to describing the electron subband structure in the presence of the spin-orbit interaction and strain, with the spin degree of freedom included. Uniaxial tensile stress along [110] direction lifts the degeneracy between the valleys completely in (001) silicon films. This results in a giant spin lifetime enhancement.
Recently, we have developed an analytical model which explains how the spin injection in any arbitrary direction additionally modifies the spin lifetime in the sample. A twofold enhancement (see Fig. 1) of spin lifetime is predicted when spin is injected in-plane of the sample, compared to when injected along the perpendicular-plane direction. The long lifetime in such a film is essential to build spin interconnects for all-spin logic devices, and the developed direction sensitive model can be used as an extra degree of freedom for designing such circuits.
Fig. 1: The variation of the normalized spin lifetime with the spin injection orientation angle (measured from the perpendicular-plane) at any fixed value for strain is shown.
