  Atomic force microscopy is based on tip sample interaction, which is
determined by the properties of tip and sample. Unfortunately, in particular in
ambient conditions the tip as well as the sample are contaminated, and it is
not clear how this contamination may affect data in Atomic Force Microscopy
(AFM) applications. In the present work we propose to use on the one hand AFM
imaging of the cantilever chips and on the other hand multidimensional AFM
spectroscopy techniques to characterize the state of contamination of the tip
sample system. We find that typically AFM cantilevers may be severely
contaminated when taken from typical packaging boxes that have been opened for
a long time. In addition, by acquisition spectroscopy data as a function of
tip-sample voltage and tip-sample distance, we are able to determine the
Hamaker constant of the system, which depends strongly on the contamination
within the tip-sample system. This method allows for in-situ characterization
of the tip-sample system using only AFM techniques.
