Calibration of an optical fluorescence method for film thickness measurement

We describe the calibration of a technique allowing quantitative measurements of industrial coatings with thicknesses as small as 10-20 nm. Wax films doped with fluorescent rhodamine dye have been deposited by an electrospray method onto an optically flat surface of aluminium-coated glass. The films were of 220-450 nm peak thickness, which we measured with an optical profilometer using laser triangulation. Possession of a set of films allowing an absolute calibration of the fluorescence intensity versus thickness to be achieved for application in trials of the fluorescence method for measuring coating thicknesses of 10-20 nm under industrial process conditions.