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

Careful NMR measurements on a very lightly-doped reference silicon sample provide a convenient highly precise and accurate secondary chemical shift reference standard for (29)Si MAS-NMR applicable over a wide temperature range. The linear temperature-dependence of the (29)Si chemical shift measured in this sample is used to refine an earlier presentation of the paramagnetic (high-frequency) (29)Si 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 100-470 K for all samples in the carrier concentration range from 2×10(18) cm(-3) to 8×10(19) cm(-3). This trend is qualitatively similar to that previously observed for the two-orders of magnitude larger (31)P impurity NMR resonance shifts in the same temperature and concentration ranges. The (29)Si and (31)P 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.