Interference enhanced Raman scattering of hydrogenated amorphous silicon revisited

We report interference enhanced Raman scattering (IERS) of very thin and hi ghly absorbing (alpha > 10(5) cm(-1)) device-quality hydrogenated amorphous silicon (a-Si:H) films. The IERS technique, in general, can give a gain of 10-10(3), depending on the optical constants of the material. The potentia l of this method is demonstrated experimentally using device-quality a-Si:H films at a wavelength of 514 nm. IERS is shown to produce an intensity gai n (G) of 50 in the scattered intensity of a thin (19 nm) a-Si:H film as com pared with the poor signal obtained for a thick specimen (1 mum) using conv entional Raman scattering in backscattering configuration. The TA- and TO-l ike signatures of the enhanced spectra stand out clearly, thus being suitab le for the structural characterization of this material. It is also shown t hat the intensity enhancement effect decreases when the incident radiation wavelength is changed to 604 nm, thus deviating from the required interfere nce condition. IERS can have important applications in the study of many ma terials, such as metals, metallic alloys, semiconductors and surface adsorb ates. Copyright (C) 2001 John Wiley & Sons, Ltd.