title: Location and Electronic Nature of Phosphorus in the Si Nanocrystal--SiO2 System.
abstract: Up to now, no consensus exists about the electronic nature of phosphorus (P) as donor for SiO2-embedded silicon nanocrystals (SiNCs). Here, we report on hybrid density functional theory (h-DFT) calculations of P in the SiNC/SiO2 system matching our experimental findings. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxide interface shell and in the SiO2 matrix were evaluated. Atom probe tomography (APT) and its statistical evaluation provide detailed spatial P distributions. For the first time, we obtain ionisation states of P atoms in the SiNC/SiO2 system at room temperature using X-ray absorption near edge structure (XANES) spectroscopy, eliminating structural artefacts due to sputtering as occurring in XPS. K energies of P in SiO2 and SiNC/SiO2 superlattices (SLs) were calibrated with non-degenerate P-doped Si wafers. results confirm measured core level energies, connecting and explaining XANES spectra with h-DFT electronic structures. While P can diffuse into SiNCs and predominantly resides on interstitial sites, its ionization probability is extremely low, rendering P unsuitable for introducing electrons into SiNCs embedded in SiO2. Increased sample conductivity and photoluminescence (PL) quenching previously assigned to ionized P donors originate from deep defect levels due to P.
authors.affiliation: 1] Integrated Material Design Centre (IMDC), UNSW, Sydney, Australia [2] School of Photovoltaic and Renewable Energy Engineering (SPREE), UNSW, Sydney, Australia.
authors.forename: Dirk
authors.initials: D
authors.lastname: König
authors.affiliation: Laboratory of Nanotechnology, Dept. of Microsystems Engineering (IMTEK), University of Freiburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Gutsch
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany.
authors.forename: Hubert
authors.initials: H
authors.lastname: Gnaser
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wahl
authors.affiliation: Institute for Surface and Thin Film Analysis (IFOS) Ltd., Kaiserslautern, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kopnarski
authors.affiliation: ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Göttlicher
authors.affiliation: ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Steininger
authors.affiliation: Laboratory of Nanotechnology, Dept. of Microsystems Engineering (IMTEK), University of Freiburg, Germany.
authors.forename: Margit
authors.initials: M
authors.lastname: Zacharias
authors.affiliation: Laboratory of Nanotechnology, Dept. of Microsystems Engineering (IMTEK), University of Freiburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hiller