Overhauser shift of the electron spin-resonance line of Si:P at the metal-insulator transition: II. ²⁹Si contribution

Abstract:

The electron-spin resonance (ESR) line of delocalised electrons shifts upon saturation due to the hyperfine interaction with the dynamically polarized nuclear spins. The ²⁹ Si part of the Overhauser shift of the ESR line of phosphorus doped silicon (Si:P) is separated in the concentration range 2.7 ... 7.3×10 ¹⁸ / cm ³ covering the metal-insulator transition. The Overhauser shift profiles, recorded versus ²⁹ Si nuclear magnetic resonance (NMR) frequency, are asymmetric. Their dependence on temperature and ESR saturation compares reasonably with simulations. Time and NMR frequency dependence of the dynamic nuclear polarization is studied in detail. No pronounced variation of the ²⁹ Si Overhauser shift profiles with P concentration is observed, but the maximum value of the shift profile decreases with increasing P concentration. In contrast to standard ²⁹ Si NMR results, these measurements reveal the behaviour of the ²⁹ Si nuclei close to the P doping sites.