Plasmas and Polymers, Vol. 5, No. 1, 2000 A Surface Masking Technique for the Determination of Plasma Polymer Film Thickness by AFM Patrick G. Hartley, 1,2 Helmut Thissen, 1 Tharshan Vaithianathan, 1 and Hans J. Griesser 1 Received May 25, 2000; accepted August 16, 2000 A method for the determination of coating film thicknesses at nanometer resolution based on surface masking and atomic force microscopy (AFM) is described. A polymeric mask is used to cover part of a substrate during the deposition of thin polymeric coatings by plasma polymerization, allowing the production of well defined polymer steps of heights of a few tens of nanometers. Tapping mode AFM has been employed to analyze the topography of these steps at high resolution. This method has also allowed accurate measurement of the kinetics of the deposition of plasma polymer films over a range of exposure times. XPS analysis of different substrate surfaces following mask removal found barely detectable residues, suggesting that the underlying surface chemistry remains unchanged, and accessi- ble for further modification. In combination with quartz crystal microgravimetry, the method has been applied to the measurement of the density of plasma polymer coatings in the thickness range 4–50 nm. KEY WORDS: Plasma polymer; AFM; density; thickness. 1. INTRODUCTION The application of thin polymer coatings to bulk materials is an important means of modifying interfacial properties. The aim may be to protect the material from chemical or physical attack whilst retaining it’s internal physical properties, to increase the efficiency of bonding between surfaces (with the film acting as an adhesion promoter), or to engineer an interface tailored to a specific application. In the latter case, this may facilitate attachment of specific chemistries, and/or modulation of non-specific surface reactions such 1 CSIRO Molecular Science, Bag 10, Clayton South, Victoria 3169, Australia. 2 Author to whom correspondence should be addressed at e-mail: Patrick.Hartley@molsci. csiro.au 47 1084-0184/00/0300-0047$18.00/0  2000 Plenum Publishing Corporation