Optical characterization of nanocrystals in silicon rich oxide superlattices and porous silicon

E. Agocs, P. Petrik, S. Milita, L. Vanzetti, S. Gardelis, A. G. Nassiopoulou, G. Pucker, R. Balboni, M. Fried

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

We propose to analyze ellipsometry data by using effective medium approximation (EMA) models. Thanks to EMA, having nanocrystalline reference dielectric functions and generalized critical point (GCP) model the physical parameters of two series of samples containing silicon nanocrystals, i.e. silicon rich oxide (SRO) superlattices and porous silicon layers (PSL), have been determined. The superlattices, consisting of ten SRO/SiO2 layer pairs, have been prepared using plasma enhanced chemical vapor deposition. The porous silicon layers have been prepared using short monopulses of anodization current in the transition regime between porous silicon formation and electropolishing, in a mixture of hydrofluoric acid and ethanol. The optical modeling of both structures is similar. The effective dielectric function of the layer is calculated by EMA using nanocrystalline components (nc-Si and GCP) in a dielectric matrix (SRO) or voids (PSL). We discuss the two major problems occurring when modeling such structures: (1) the modeling of the vertically non-uniform layer structures (including the interface properties like nanoroughness at the layer boundaries) and (2) the parameterization of the dielectric function of nanocrystals. We used several techniques to reduce the large number of fit parameters of the GCP models. The obtained results are in good agreement with those obtained by X-ray diffraction and electron microscopy. We investigated the correlation of the broadening parameter and characteristic EMA components with the nanocrystal size and the sample preparation conditions, such as the annealing temperatures of the SRO superlattices and the anodization current density of the porous silicon samples. We found that the broadening parameter is a sensitive measure of the nanocrystallinity of the samples, even in cases, where the nanocrystals are too small to be visible for X-ray scattering. Major processes like sintering, phase separation, and intermixing have been revealed as a function of annealing of the SRO superlattices.

Original languageEnglish
Pages (from-to)3002-3005
Number of pages4
JournalThin Solid Films
Volume519
Issue number9
DOIs
Publication statusPublished - Feb 28 2011

Fingerprint

Porous silicon
Superlattices
Silicon
porous silicon
silicon oxides
Nanocrystals
Oxides
superlattices
nanocrystals
silicon
critical point
approximation
Annealing
Hydrofluoric Acid
electropolishing
Electrolytic polishing
Hydrofluoric acid
annealing
hydrofluoric acid
Ellipsometry

Keywords

  • Effective medium approximation
  • Ellipsometry
  • GCP
  • Generalized critical point
  • MDF
  • Nanocrystal

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Metals and Alloys
  • Surfaces, Coatings and Films
  • Surfaces and Interfaces

Cite this

Optical characterization of nanocrystals in silicon rich oxide superlattices and porous silicon. / Agocs, E.; Petrik, P.; Milita, S.; Vanzetti, L.; Gardelis, S.; Nassiopoulou, A. G.; Pucker, G.; Balboni, R.; Fried, M.

In: Thin Solid Films, Vol. 519, No. 9, 28.02.2011, p. 3002-3005.

Research output: Contribution to journalArticle

Agocs, E, Petrik, P, Milita, S, Vanzetti, L, Gardelis, S, Nassiopoulou, AG, Pucker, G, Balboni, R & Fried, M 2011, 'Optical characterization of nanocrystals in silicon rich oxide superlattices and porous silicon', Thin Solid Films, vol. 519, no. 9, pp. 3002-3005. https://doi.org/10.1016/j.tsf.2010.11.072
Agocs, E. ; Petrik, P. ; Milita, S. ; Vanzetti, L. ; Gardelis, S. ; Nassiopoulou, A. G. ; Pucker, G. ; Balboni, R. ; Fried, M. / Optical characterization of nanocrystals in silicon rich oxide superlattices and porous silicon. In: Thin Solid Films. 2011 ; Vol. 519, No. 9. pp. 3002-3005.
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