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Thin Film Cavity Ringdown Spectroscopy and Second Harmonic Generation on Thin a-Si:H Films

Published online by Cambridge University Press:  01 February 2011

I.M.P. Aarts ,
B. Hoex ,
J.J.H. Gielis ,
C.M. Leewis ,
A.H.M. Smets ,
R. Engeln ,
M. Nesládek ,
W.M.M. Kessels  and
M.C.M. van de Sanden
I.M.P. Aarts
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
B. Hoex
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
J.J.H. Gielis
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
C.M. Leewis
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
A.H.M. Smets
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
R. Engeln
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
M. Nesládek
Affiliation:
Institute for Materials Research, Limburgs Universitair Centrum, Wetenschapspark 1, B-3590 Diepenbeek, Belgium
W.M.M. Kessels
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
M.C.M. van de Sanden
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Abstract

A set of 8 rf deposited a-Si:H thin films of various thickness (4-1031nm) have been used to explore the applicability of two optical techniques, thin film cavity ringdown spectroscopy (tfCRDS) and second harmonic generation (SHG), for the measurement of small defect-related absorptions. In this paper we will give a first overview of the different aspects of these techniques, which are novel in the field of amorphous silicon materials. It is shown that tf-CRDS is capable of measuring defect-related absorptions (associated with dangling bonds) as small as 10-7 for a single measurement, without the need for elaborate calibration procedures. The results are compared with photothermal deflection spectroscopy (PDS) for a broad spectral range (0.7 – 1.7 eV) and show good agreement. Furthermore the existence of a defect-rich surface layer with a defect density of 1.1×1012 cm-2 has been proven. The absorption spectrum of a 4 nm thin film has revealed a different spectral signature than a bulk dominated (1031 nm) film. The SHG experiments on a-Si:H films have shown that the second harmonic signal arises from the surface states and polarization dependent studies have revealed that the surface states probed have an ∞m-symmetry. From this it can be deduced that the absorbing surface states are isotropically distributed. A spectral scan suggests that the second harmonic signal, whose origin has not been unrevealed yet, has a resonance at an incident photon energy of 1.22 eV.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 762: Symposium A – Amorphous and Nanocrystalline Silicon-Based Films – 2003 , 2003 , A19.8
Copyright
Copyright © Materials Research Society 2003

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