Abstract: We have developed an improved vapor-phase deposition method and apparatus for the application of organic films/coatings containing a variety of functional groups on substrates. Most substrates can be coated using the method of the invention. The substrate surface is halogenated using a vaporous halogen-containing compound, followed by a reaction with at least one organic molecule containing at least one nucleophilic functional group capable of reacting with a halogenated substrate surface. The halogenation of the substrate surface and the subsequent reaction with the organic molecule nucleophilic functional group are carried out in the same process chamber in a manner such that the halogenated substrate surface does not lose its functionality prior to reaction with the nucleophilic functional group(s) on the organic molecule. Typically the process chamber is operated under a pressure ranging from about 1 mTorr to about 10 Torr.