Inherent paramagnetic defects in layered Si/SiO{sub 2} superstructures with Si nanocrystals
- Department of Physics and INPAC-Institute for Nanoscale Physics and Chemistry, University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven (Belgium)
- IMTEK, Albert Ludwigs University Freiburg, Georges Koehler Alley 103, 79110 Freiburg (Germany)
An extensive electron spin resonance (ESR) analysis has been carried out on structures comprised of Si nanoparticles ({approx}2 nm across) embedded in a regular pattern in an amorphous SiO{sub 2} matrix, fabricated by the SiO/SiO{sub 2} superlattice approach, with the intent to reveal and quantify occurring paramagnetic defects. The as-grown state is found to exhibit only a Si dangling bond (DB) signal, which through combination of first and second harmonic X-, K-, and Q-band observations in combination with computer spectra simulation, could be conclusively disentangled as solely comprised of overlapping powder pattern spectra of P{sub b(0)} and P{sub b1} defects, the archetypal intrinsic defects of the Si/SiO{sub 2} interface, with no evidence for a D line (Si DBs in disordered Si). This indicates a full crystalline system of randomly oriented Si nanocrystals (NCs). The P{sub b(0)}/P{sub b1} defect system, pertaining to the NC-Si/SiO{sub 2} interfaces, is found to be both qualitatively and quantitatively much alike that of standard (high-quality) thermal Si/SiO{sub 2}. The system is inherent, remaining unaffected by subsequent UV/vacuum UV irradiations. Relying on the known properties of P{sub b}-type defects in standard microscopic Si/SiO{sub 2}, the data would comply with Si nanocrystallites, in average, predominantly bordered by (111) and (100) facets, perhaps with morphology, schematically, of [100] truncated (111) octahedrons. Based on independent NC particles counting, there appears a P{sub b}-type center at {approx}71% of the Si NCs indicating the latter to be comprised of two subsystems-with or without an incorporated strain relaxing interface defect-which in that case will exhibit drastically different defect-sensitive properties, such as, e.g., photoluminescence (PL). Upon additional optical irradiation, two more defects appear, i.e., the SiO{sub 2}-associated E{sub {gamma}}{sup '} and EX centers, where the observed density of the former, taken as criterion, indicates the SiO{sub 2} matrix to be of standard thermal oxide quality. Thus, the properties of the revealed crucial intrinsic point defects bear out a high quality of both the NC-Si/SiO{sub 2} interfaces and the embedding SiO{sub 2}, alike that of standard thermal Si/SiO{sub 2}. In combination with H passivation/depassivation treatments, the degrading impact of the optical excitation ({approx}360 nm) itself used during PL measurements has been studied, revealing weak ESR reactivation of P{sub b(0)}, P{sub b1}, and E{sub {gamma}}{sup '} defects.
- OSTI ID:
- 21185920
- Journal Information:
- Journal of Applied Physics, Vol. 104, Issue 10; Other Information: DOI: 10.1063/1.2966690; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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