Artifacts in Atomic Force Microscopy of Biological Samples

Atomic force microscopy (AFM) is a frequently used method applicable also to biological studies due to its capability of measuring in native environment. Sharp Si, Si3N4 or C (carbon nanotubes, diamond, diamond coated) cantilevers repeatedly touching a sample are used in this method as sensitive probes. It is possible to control the interaction between the tip and the sample in order to make less invasive measurements or, conversely, to modify the sample. However, AFM images often contain features which are not present on the sample in reality, but are a direct result of the measurements itself. Such structures or features are denoted as artifacts. The artifacts arise from various reasons. Some of them can be avoided during measurements, other ones are inherent. The artifacts shown in this chapter are divided into several categories based on the part of AFM which is responsible for them. Examples of many artifacts are presented and their reasons are explained. This chapter will be helpful for AFM users who observe strange effects, presumably related to the AFM technique, but do not know their reason. This chapter can also answer questions about the validity of imaged features as well as their accuracy.