The interfacial bonding and mixing between evaporated aluminum and a vapor deposited Teflon AF (abbreviated to AF) film have been investigated with X-ray photoelectron spectroscopy. Graphite carbon (C-C), and aluminum carbide (Al-C), oxide (Al-O-C) and fluoride (Al-F) are formed when aluminum atoms are deposited on to the AF film. With increasing deposition of aluminum, the concentrations of these newly formed components increase gradually. Moreover, in situ annealing results in remarkable increases in the C-C, Al-C, Al-O-C and Al-F configurations and a decrease in metallic aluminum. No significant diffusion of aluminum into the AF film was observed during the annealing. The Al compounds form a layer at the Al/AF interface that acts as an adhesion promoter and diffusion barrier.