AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM11
Spectroscopic Second Harmonic Generation on Hydrogenated Amorphous Silicon Surfaces and Interfaces

Wednesday, November 17, 2004, 11:40 am, Room 210C

Session: Semiconductor Surface and Interface Structure
Presenter: C.M. Leewis, Eindhoven University of Technology, The Netherlands
Authors: C.M. Leewis, Eindhoven University of Technology, The Netherlands
J.J.H. Gielis, Eindhoven University of Technology, The Netherlands
I.M.P. Aarts, Eindhoven University of Technology, The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Optical Second Harmonic Generation (SHG) is applied on hydrogenated amorphous silicon (a-Si:H) films on fused silica substrates to investigate the presence of surface and buried interface dangling bonds. For amorphous material, e.g. a-Si:H, the SHG technique is surface-specific and therefore originates from both the film surface and the film-substrate interface. The origin of the second harmonic signal can be due to dangling bonds and strained bonds. In addition, optical interference effects can enhance the signal for certain wavelength-film thickness combinations. The technique is applied both ex situ, and in situ in a UHV setup on hot wire grown films. An incident polarization scan is performed for both p- and s-polarized SHG radiation while SHG is also measured while rotating the sample around the axis normal to the substrate. It has been established that the SHG can be described by the infinity-m symmetry class, which is in agreement with the amorphous nature of the material. In situ spectroscopic scans are performed with a probe photon energy in the range 1.0-1.6 eV for different polarizations. These scans are in agreement with ex situ scans on plasma deposited a-Si:H. The observed resonant peaks correspond possibly to surface and interface dangling bond states@footnote 1@. The presence of dangling bonds is investigated with real time measurements. These experiments during film growth have already shown that the SHG intensity increases instantly when growth is started, and gradually decreases during further growth. In addition, it is shown that the maximum SHG intensity increases for increasing substrate deposition temperatures in the range 520-720 K. The consequences for a possible surface and interface concentration of dangling bonds will be discussed. @FootnoteText@ @footnote 1@Pedersen et al., Phys. Rev. B 52, R2277 (1995).