Activation and chemical modification of the molecularly smooth mica surface were investigated. Exposure to water vapor plasma made the mica surface reactive enough to be silanized with gaseous chlorosilanes or alkoxysilanes. Conditions for silanization were optimized to immobilize various functional groups onto mica surface. By selection of appropriate reaction conditions, functional units such as trifluoromethyl, mercapto, amino, dimethylamino, isocyanate, urea, 4,5-dihydroimidazole, and chlorobenzyl groups were covalently bound to the mica surface at densities close to monolayer coverage. Improved simulation of X-ray photoelectron spectral data was essential for the surface characterization. Urease could be immobilized on a chlorobenzylated mica surface. Immobilized urease was retained upon washing with an aqueous surfactant and gave atomic force microscopy (AFM) images of 10 x 20-30 nm size which appeared to be enlarged due to the finite size of the AFM tip. These images were stable during several repeated scans.