Basic principles of atomic force microscopy

This chapter presents basic principles of operation of an atomic force microscope (AFM) that outlines the most common imaging modes and describes the acquisition of force distance measurements and techniques to calibrate cantilever spring constants. The AFM, also referred to as the scanning force microscope (SFM), is a part of a larger family of instruments termed as the scanning probe microscopes. These also include the scanning tunneling microscope (STM) and scanning near field optical microscope (SNOM), among others. The common factor in all SPM techniques is the use of a very sharp probe, which is scanned across a surface of interest, with the interactions between the probe and the surface being used to produce a very high resolution image of the sample, potentially to the subnanometer scale, depending upon the technique and sharpness of the probe tip. The AFM was first described as a new technique for imaging the topography of surfaces to a high resolution. It was created as a solution to the limitations of the STM, which was able to image only conductive samples in vacuum. The AFM has a number of advantages over electron microscope techniques, primarily its versatility in being able to take measurements in air or fluid environments rather than in high vacuum, which allows the imaging of polymeric and biological samples in their native state. It is highly adaptable with probes being able to be chemically fictionalized to allow quantitative measurement of interactions between many different types of materials-a technique often referred to as chemical force microscopy. © 2009