Thin film cavity ringdown spectroscopy and second harmonic generation on thin a-Si:H films

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, M. C.M. Van de Sanden

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

1 Citation (Scopus)


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 (tf-CRDS) 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.

Original languageEnglish
Title of host publicationAmorphous and nanocrystalline silicon-based films - 2003 : symposium held April 22 - 25, 2003, San Francisco, California, U.S.A.
EditorsJ.R. Abelson
Place of PublicationWarrendale
PublisherMaterials Research Society
Number of pages6
ISBN (Print)1-558-99699-0
Publication statusPublished - 1 Dec 2003
Event2003 Amorphous and Nanocrystalline Silicon-Based Films Symposium - San Francisco, United States
Duration: 22 Apr 200325 Apr 2003

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Conference2003 Amorphous and Nanocrystalline Silicon-Based Films Symposium
Country/TerritoryUnited States
CitySan Francisco


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