Engineering silicon nanocrystals: Theoretical study of the effect of codoping with boron and phosphorus
|Title||Engineering silicon nanocrystals: Theoretical study of the effect of codoping with boron and phosphorus|
|Publication Type||Palaiseau Article|
|Author Address|| |
Iori, F (Reprint Author), Univ Modena & Reggio Emilia, CNR, CNISM, Via Campi 213-A, I-41100 Modena, Italy. Univ Modena & Reggio Emilia, CNR, CNISM, I-41100 Modena, Italy. Univ Modena & Reggio Emilia, Dipartimento Fis, I-41100 Modena, Italy. Univ Modena & Reggio Emilia, CNR, INFM S3, I-42100 Modena, Italy. Univ Modena & Reggio Emilia, Dipartimento Sci Metodi Ingn, I-42100 Modena, Italy. Univ Naples Federico 2, CNR, INFM Coherentia, I-80126 Naples, Italy. Univ Naples Federico 2, Dipartimento Sci Fis, I-80126 Naples, Italy. Univ Roma Tor Vergata, Dipartimento Fis, CNR, INFM, I-00133 Rome, Italy. Univ Roma Tor Vergata, European Theoret Spect Facil, I-00133 Rome, Italy.
|Iori, F, Degoli, E, Magri, R, Marri, I, Cantele, G, Ninno, D, Trani, F, Pulci, O, Ossicini, S|
|Year of Publication||2007|
|Journal||PHYSICAL REVIEW B|
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 1.1 to 1.8 nm 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.