Temperature-dependent 29Si NMR resonance shifts in lightly- and heavily-doped Si:P.

Abstract: Careful NMR measurements on a very lightly-doped reference silicon sample provide a convenient highly precise and accurate secondary chemical shift reference standard for 29Si MAS-NMR applicable over a wide temperature range. The linear temperature-dependence of the 29Si chemical shift measured in this sample is used to refine an earlier presentation of the paramagnetic (high-frequency) 29Si resonance shifts in heavily-doped n-type silicon samples near the metal–nonmetal transition. The data show systematic decreases of the local magnetic fields with increasing temperature in the range 100–470K for all samples in the carrier concentration range from 2×1018 cm−3 to 8×1019 cm−3. This trend is qualitatively similar to that previously observed for the two-orders of magnitude larger 31P impurity NMR resonance shifts in the same temperature and concentration ranges. The 29Si and 31P resonance shifts are not related by a simple scaling factor, however, indicating that impurity and host nuclei are affected by different subsets of partially-localized extrinsic electrons at all temperatures. [Copyright &y& Elsevier]