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Thin film cavity ringdown spectroscopy and second harmonic generation on thin a-Si:H films
- Source :
- Amorphous and nanocrystalline silicon-based films-2003 : symposium held April 22-25, 2003, San Francisco, California, U.S.A., 111-116, STARTPAGE=111;ENDPAGE=116;TITLE=Amorphous and nanocrystalline silicon-based films-2003 : symposium held April 22-25, 2003, San Francisco, California, U.S.A.
- Publication Year :
- 2003
- Publisher :
- Materials Research Society, 2003.
-
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 (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.
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- Amorphous and nanocrystalline silicon-based films-2003 : symposium held April 22-25, 2003, San Francisco, California, U.S.A., 111-116, STARTPAGE=111;ENDPAGE=116;TITLE=Amorphous and nanocrystalline silicon-based films-2003 : symposium held April 22-25, 2003, San Francisco, California, U.S.A.
- Accession number :
- edsair.narcis........b160a526621ff7a425a0cc63c778b13c