Measurement of the friction of thin films by means of a quartz microbalance in the presence of a finite vapor pressure

In recent years, the quartz-crystal microbalance technique (QCM) has been succesfully applied to the field of nanotribology. In this paper we examine the effect of a finite vapor pressure on the accuracy of thin-film friction measurements taken with a QCM by solving the Navier-Stokes equation of the combined system quartz-crystal-adsorbed film-bulk vapor. We also discuss the details of the calibration procedure of the QCM carried out at both room temperature and low temperature, and describe the data acquisition and analysis specific to tribological applications. Finally, we present some preliminary data of the friction of a Kr monolayer adsorbed on gold at low temperatures that show the sliding of the film.