Ultrathin Aluminosilicate Films from Langmuir−Blodgett Multilayers

Abstract

Multilayer films incorporating both silicon and aluminum have been prepared by Langmuir−Blodgett deposition and subsequently decomposed by exposure to ultraviolet ozone (UVO) to yield films with a composition consistent with the formation of an aluminosilicate. The morphology of the deposited films was studied by atomic force microscopy both before and after UVO treatment, and their chemical structures and compositions were investigated by FTIR and XPS. Two film systems were investigated, namely, cyclic polysiloxanes with carboxylic acid side groups and octadecyltrimethoxysilane (OTMS). Aluminum was introduced into the films from a 10-5 M aluminum nitrate subphase at pH ∼ 4 in the first case and at pH = 9.5 in the second. It is shown that uptake of aluminum and control of aluminosilicate formation is likely to be easier with the OTMS system. It is also shown that inclusion of an ether linkage in the hydrophobic tails of the polysiloxanes leads to a much more rapid removal of carbon from the films during U...