ELASTIC DEFORMATIONS OF TIP AND SAMPLE DURING ATOMIC-FORCE MICROSCOPEMEASUREMENTS

Two established models, based on continuum mechanics, are discussed to describe the elastic deformation of the tip and the sample in the ato mic force microscope. We present arguments why the elastic deformation of a surface is more rigorously described by Sneddon mechanics rather than by the habitually used Hertzian mechanics. The results presented here show that elastic deformations are an important issue for measur ements with the atomic force microscope. We demonstrate how elastic de formations impose limits to the capability of the atomic force microsc ope to image at true atomic resolution and how elastic deformations ca n be used to measure local elastic properties of a sample. Against the commonly accepted assumption of a ''rigid'' tip, we show that the ela stic deformation of the tip can become a significant factor, when imag ing hard samples. With few exceptions, the atomic force microscope has not been operated at true atomic resolution so far and more complex c ontrast mechanisms, with multiple atom interaction, must be considered . (C) 1996 American Vacuum Society.