Engineering silicon nanocrystals: Theoretical study of the effect of codoping with boron and phosphorus

Federico Iori, Elena Degoli, Rita Magri, Ivan Marri, G. Cantele, D. Ninno, F. Trani, O. Pulci, and Stefano Ossicini
Phys. Rev. B 76, 085302 – Published 1 August 2007

Abstract

We show that the optical and electronic properties of nanocrystalline silicon can be efficiently tuned using impurity doping. In particular, we give evidence, by means of ab initio calculations, that by properly controlling the doping with either one or two atomic species, a significant modification of both the absorption and the emission of light can be achieved. We have considered impurities, either boron or phosphorous (doping) or both (codoping), located at different substitutional sites of silicon nanocrystals with size ranging from 1.1to1.8nm in diameter. We have found that the codoped nanocrystals have the lowest impurity formation energies when the two impurities occupy nearest neighbor sites near the surface. In addition, such systems present band-edge states localized on the impurities, giving rise to a redshift of the absorption thresholds with respect to that of undoped nanocrystals. Our detailed theoretical analysis shows that the creation of an electron-hole pair due to light absorption determines a geometry distortion that, in turn, results in a Stokes shift between adsorption and emission spectra. In order to give a deeper insight into this effect, in one case we have calculated the absorption and emission spectra beyond the single-particle approach, showing the important role played by many-body effects. The entire set of results we have collected in this work give a strong indication that with the doping it is possible to tune the optical properties of silicon nanocrystals.

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  • Received 23 January 2007

DOI:https://doi.org/10.1103/PhysRevB.76.085302

©2007 American Physical Society

Authors & Affiliations

Federico Iori1, Elena Degoli2, Rita Magri1, Ivan Marri2, G. Cantele3, D. Ninno3, F. Trani3, O. Pulci4, and Stefano Ossicini2

  • 1CNISM-CNR and Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/A, I-41100 Modena, Italy
  • 2CNR-INFM-S3 and Dipartimento di Scienze e Metodi dell'Ingegneria, Università di Modena e Reggio Emilia, via Amendola 2 Padiglione Morselli, I-42100 Reggio Emilia, Italy
  • 3CNR-INFM-Coherentia and Dipartimento di Scienze Fisiche, Università di Napoli “Federico II,” Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy
  • 4European Theoretical Spectroscopy Facility (ETSF) and CNR-INFM, Dipartimento di Fisica, Università di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy

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Issue

Vol. 76, Iss. 8 — 15 August 2007

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