STUDY BY REAL-TIME ELLIPSOMETRY OF THE GROWTH OF AMORPHOUS AND MICROCRYSTALLINE SILICON THIN-FILMS COMBINING GLOW-DISCHARGE DECOMPOSITION AND UV-LIGHT IRRADIATION

We present here the application of spectroscopic phase modulated ellip sometry (SPME) to the study of the growth of amorphous and microcrysta lline silicon thin films combining plasma-enhanced chemical vapor depo sition (PECVD) and excimer laser irradiation. Our results show that la ser fluence is a critical parameter in UV-assisted deposition. When we increase the laser fluence we observe a gradual transition from hydro genated amorphous silicon (a-Si:H) to an a-Si:H with greater roughness and porosity, then to a very dense a-Si:H, after that to a dense micr ocrystalline silicon (muc-Si) material, and finally to a porous microc rystalline material. The crystallization, after and during plasma depo sition, is characterized by the evolution of the imaginary part of the pseudo-dielectric function which allows us to identify the threshold of crystallization in the two cases. Moreover, the substrate temperatu re is found to activate the crystallization process in UV-assisted PEC VD.