Linear and nonlinear optical properties of Si nanocrystals in SiO{sub 2} deposited by plasma-enhanced chemical-vapor deposition

Journal Article · Sat Mar 15 00:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2896454· OSTI ID:21134006

Hernandez, S; Pellegrino, P; Martinez, A; Lebour, Y; Garrido, B ^[1]; Spano, R; Cazzanelli, M; Daldosso, N; Pavesi, L ^[2]; Jordana, E; Fedeli, J M ^[3]

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1. EME, Departament d'Electronica, IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain)
2. Laboratorio Nanoscienze, Dipartimento di Fisica, Universita di Trento, via Sommarive 14, I-38050 Povo, Trento (Italy)
3. CEA-LETI, MINATEC, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

Linear and nonlinear optical properties of silicon suboxide SiO{sub x} films deposited by plasma-enhanced chemical-vapor deposition have been studied for different Si excesses up to 24 at. %. The layers have been fully characterized with respect to their atomic composition and the structure of the Si precipitates. Linear refractive index and extinction coefficient have been determined in the whole visible range, enabling to estimate the optical bandgap as a function of the Si nanocrystal size. Nonlinear optical properties have been evaluated by the z-scan technique for two different excitations: at 0.80 eV in the nanosecond regime and at 1.50 eV in the femtosecond regime. Under nanosecond excitation conditions, the nonlinear process is ruled by thermal effects, showing large values of both nonlinear refractive index (n{sub 2}{approx}-10{sup -8} cm{sup 2}/W) and nonlinear absorption coefficient ({beta}{approx}10{sup -6} cm/W). Under femtosecond excitation conditions, a smaller nonlinear refractive index is found (n{sub 2}{approx}10{sup -12} cm{sup 2}/W), typical of nonlinearities arising from electronic response. The contribution per nanocrystal to the electronic third-order nonlinear susceptibility increases as the size of the Si nanoparticles is reduced, due to the appearance of electronic transitions between discrete levels induced by quantum confinement.

• OSTI ID: 21134006
• Journal Information: Journal of Applied Physics, Vol. 103, Issue 6; Other Information: DOI: 10.1063/1.2896454; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION
CHEMICAL VAPOR DEPOSITION
CRYSTAL GROWTH
EXCITATION
LAYERS
NANOSTRUCTURES
NONLINEAR OPTICS
NONLINEAR PROBLEMS
PRECIPITATION
REFRACTIVE INDEX
SEMICONDUCTOR MATERIALS
SILICON OXIDES
TEMPERATURE DEPENDENCE
THIN FILMS