PhD ceremony Mr. S. Sharma: Electrical creation of spin polarization in silicon devices with magnetic tunnel contacts

PhD ceremony: Mr. S. Sharma, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Electrical creation of spin polarization in silicon devices with magnetic tunnel contacts

Promotor(s): prof. B.J. van Wees

Faculty: Mathematics and Natural Sciences

Spintronics is an emerging technology for information storage and computing that, unlike traditional electronics, uses the spin of electrons rather than charge to represent digital data. Electronic devices with spin functionality may enable the design of new systems that combine non-volatile memory functionality with low-power, high-density computing. A large impact is expected if this is achieved in silicon, the mainstream semiconductor material of electronic circuits. This thesis describes the development and study of the main building blocks of such a silicon spintronics technology, namely, the creation, detection and manipulation of spins in silicon at room temperature.

The earlier efforts in this direction were limited to low temperature. The research work described in this thesis starts with the successful demonstration of the all-electrical injection and detection of the spins in silicon, and of the manipulation of the spins via the Hanle effect, all at room temperature. It was shown that this can be achieved in a robust way using ferromagnetic tunnel contacts to silicon. Tunnel contacts with different tunnel oxide materials and types of ferromagnet were examined and the variation of the spin signals with applied voltage, current density, temperature, and tunnel barrier thickness was investigated. Control experiments unambiguously established that the unexpected large spin signals are genuine and originate from spin-polarized tunneling and the formation of a spin accumulation. The anisotropy of tunneling in silicon/oxide/ferromagnet tunnel devices was also studied in detail. These results represent a key advancement in the development and understanding of silicon spintronics.