Influence of valley splitting on spin relaxation time in a strained thin silicon film

Abstract

The electron spin properties are promising for future spin-driven devices. In contrast to charge, spin is not a conserved quantity, and having sufficiently long spin lifetime is critical for applications. Silicon, the major material of microelectronics, also appears to be a perfect material for spintronic applications. The peculiarities of the subband structure and details of the spin propagation in ultra-thin silicon films in the presence of strain are investigated. The application of an uniaxial stress can lift the degeneracy between the remaining two valleys in a (001) silicon film. The [001] equivalent valley coupling through the Γ-point, which results in a subband splitting in a confined relaxed electron structure, is properly included. Its impact on the shear strain inflicted equivalent subband splitting is evaluated, and thereby the dependence of spin lifetime on the valley splitting is predicted. In all possible conditions, the spin lifetime is observed to be boosted by several orders of magnitude.