Preparation of stacked organosiloxane bilayers on hydrophilic and hydrophobic silicon substrates by spin coating

A simple one-step procedure for the preparation of stacked organosiloxane bilayers is demonstrated. Millimolar solutions of long-chain alkyl- and alkenyltrichlorosilanes, respectively, have been spin coated onto silicon samples with distinct hydrophilicity. After coating, the samples are characterized using optical microscopy, atomic force microscopy (AFM) and contact angle measurements. Generally, the procedure yields thin films consisting of highly aligned bilayers. The wettability of the substrates by the silane solution, however, strongly affects both the macroscopic and the microscopic homogeneity of the coatings across the surface. Cross-linking via Si-O-Si bonds appears to set in after some weeks and stabilize the films. For several days, however, the bilayers show a remarkable flexibility, i.e. using the AFM tip the self-assembling entities can be easily shifted between the distinct levels maintaining their vertical alignment.