Surface preparation influence on the initial stages of MOCVD growth of TiO_2 thin films

摘要

In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS), completed by ex situ atomic force microscopy (AFM) analyses, were performed in order to compare the initial stages of MOCVD growth of TiO_2 thin films on two different surface types. The first type was a silicon native oxide free hydrogen terminated surface and the second one was a silicon dioxide surface corresponding to a thin layer of 3.5 nm thick in situ thermally grown on silicon substrate. Si(100) was used as substrate, and the growths of TiO_2 thin films were achieved with titanium tetraisopropoxide (TTIP) as precursor under a temperature of 675℃, a pressure of 0.3 Pa and a deposition time of 1 h. Whatever the surface is, the deposited titanium amount was globally the same in the two cases. On the contrary, the deposit morphology was different: a covering layer composed of a SiO_2 and TiO_2 phases mixture on the hydrogen terminated surface, and small TiO_2 clusters homogeneously spread on the SiO_2 surface.