TY - JOUR
T1 - From amorphous to crystalline silicon nanoclusters
T2 - Structural effects on exciton properties
AU - Borrero-Gonzlez, L. J.
AU - Nunes, L. A.O.
AU - Guimarães, F. E.G.
AU - Wojcik, J.
AU - Mascher, P.
AU - Gennaro, A. M.
AU - Tirado, M.
AU - Comedi, D.
PY - 2011/12/21
Y1 - 2011/12/21
N2 - Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y=0.360.42 in Si yO 1y), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2h) annealed at various temperatures (T a=9001100°C) under either Ar or (Ar+5%H 2) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate T a can be qualitatively understood in terms of a crystalline coreamorphous shell Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing T a, the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails.
AB - Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y=0.360.42 in Si yO 1y), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2h) annealed at various temperatures (T a=9001100°C) under either Ar or (Ar+5%H 2) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate T a can be qualitatively understood in terms of a crystalline coreamorphous shell Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing T a, the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails.
UR - http://www.scopus.com/inward/record.url?scp=84855286307&partnerID=8YFLogxK
U2 - 10.1088/0953-8984/23/50/505302
DO - 10.1088/0953-8984/23/50/505302
M3 - Article
C2 - 22129528
AN - SCOPUS:84855286307
SN - 0953-8984
VL - 23
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
IS - 50
M1 - 505302
ER -