Gas-phase plasma-synthesized silicon nanocrystals (Si-NCs) are doped with boron (B) or phosphorous (P) during synthesis. The doping efficiency of B is smaller than that of P, consistent with the theoretical prediction of impurity formation energies. Despite vastly different synthesis conditions, the effect of doping on the photoluminescence (PL) of gas-phase-synthesized Si-NCs is qualitatively similar to that of Si-NCs doped during solid phase nucleation. Studies of oxidation-induced changes in PL and etching-induced changes in dopant concentration show that P resides at or near the Si-NC surface, while B is in the Si-NC cores. The oxidation of Si-NCs follows the Cabrera-Mott mechanism [N. Cabrera and N. F. Mott, Rep. Prog. Phys. 12, 163 (1948)].
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The authors are grateful to Professor David J. Norris for support in the PL measurements. Russell Anderson is thanked for the ICP-AES measurements. This work was supported primarily by the MRSEC Program of the NSF under Award No. DMR-0212302, and partially by NSF Grant No. DMI-0556163 and IGERT Grant DGE-0114372. Portions of this work were supported through the NSF NNIN Program.