Binary mixtures of self-assembled monolayers on SrTiO3: Experimental evidence for phase segregation

The formation of monolayers from mixed solutions of alkylsiloxane molecules on the surface of SrTiO3 has been studied. The monolayers were formed by self-assembly from dilute n-hexadecane solutions of two binary mixtures of long- and short-chain alkyltrichlorosilanes. These films have been studied by atomic and lateral force microscopy and wettability measurements. One mixture showed evidence of phase segregation on the vicinal surface of a SrTiO3 (001) crystal. The long-chain molecules are found to preferably adsorb at or migrate toward the step ledge, probably to increase their van der Waals interaction and minimize the surface free energy.