Spectroscopic characterisation of self-assembled monolayers of alkylsiloxanes on SrTiO3

Self-assembled monolayers of alkyltrichlorosilanes have been successfully prepared on SrTiO3 substrates. Characterisation has been performed by atomic force microscopy (AFM), wettability, ellipsometry, angle resolved X-ray photoemission spectroscopy (ARXPS) and reflection absorption infrared spectroscopy (RAIRS). It is found that dense and ordered monolayers form if environmental conditions are controlled. Good agreement is found for the ellipsometry thickness and the ARXPS thickness. From simulations of absorption spectra, we find that the molecules are oriented with an average tilt angle of −11° with respect to the surface normal on the (001) and (110) faces. On the niobium-doped SrTiO3 substrate, however, the tilt angle increases to −35°.