Photothermal laser processing of alkylsiloxane monolayers in gaseous bromine is investigated. Surface-oxidized silicon samples are coated with octadecylsiloxane monolayers and locally irradiated with a focused beam of an Ar+-laser at lambda=514 nm and a 1/e(2) spot diameter of 3 mu m. For characterization, atomic force microscopy, scanning electron microscopy, and optical microscopy in conjunction with labeling techniques and condensation experiments are used. At low laser powers, monolayer bromination in micron-sized areas is Observed. Additionally, at high laser powers, decomposition of the monolayer takes place at the center of the brominated areas. Prospects and limitations of this procedure in fabrication of multifunctional templates are discussed. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3386590]