Mixed Langmuir-Blodgett films of arachidic acid and partially fluorinated carboxylic acid on vapor-deposited silver films on a glass substrate plate have been observed with atomic force microscopy (AFM) and friction force microscopy (FFM). Phase-separated domains could be observed by lateral force measurements (FFM) but such domains could not be imaged clearly by normal force measurements with AFM because of the roughness of the silver film.