Electron spin relaxation and coherence in silicon

Spin of donors or double donors in silicon are the heart of several schemes for qubits. In the last decade there has been a revival of the pioneering continuous wave electron paramagnetic resonance (CW-EPR) investigations, started in the late 50s, of these class of impurities in silicon taking advantage of pulse-EPR techniques. In addition the availability of isotopically purified silicon-28 allowed a detailed investigation of the main relaxation mechanisms and of the coherence time when super-hyperfine interactions are mostly eliminated and spin diffusion processes suppressed. We will review the main results related to the pulse-EPR investigation of conventional donors (P, As) [1, 2], other group V impurities (Bi and N) [3, 4] and double donors (S, Se) [5, 6] focusing on spin-lattice and spin-spin relaxation processes in bulk silicon. In any silicon based, CMOS compatible, nano-electronic device a major role is played by the Si/SiO2 interface and by the well-known defects, the Pb center family, there localized. Due to sensitivity issues the investigation of the spin dynamics of these centers has not been reported so far. Taking advantage of silicon nanowires fabrication and surface/interface preparation and modification we have been able to investigate the spin relaxation mechanisms of the Pb-centers and also their interaction with the donor spin dynamics [7]. These results will be reported and discussed. 1. M. Fanciulli, P. Höfer, and A. Ponti, Physica B 340-342, 895 (2003) 2. A. Ferretti, M. Fanciulli, A. Ponti, and A. Schweiger, Phys. Rev. B 72, 235201 (2005) 3. M. Belli, M. Fanciulli, N. V. Abrosimov , Phys. Rev. B 83, 235204 (2011) 4. M. Belli, M. Fanciulli, D. Batani, Phys. Rev. B 89, 115207 (2014) 5. S. Paleari, M. Belli, M. Fanciulli, Yu. A. Astrov, ICDS 2013 6. R. Lo Nardo, et al. Phys. Rev. B 92, 165201 (2015) 7. M. Fanciulli, APS March Meeting, Baltimore, USA (2016)