The Sensitivity of Subsurface Contact Resonance Atomic Force Microscopy to Changes in the Depth of Buried Features: a Nonlinear Approach

The development of non-destructive subsurface imaging methods has been a major research topic in the past two decades. One of these is the use of Contact Resonance Atomic Force Microscopy (CR-AFM) to measure changes in contact stiffness to detect buried features. The depth of the buried feature has a large influence (or is a limiting factor) on the sensitivity and resolution of this method, which has been shown in theoretical, numerical and experimental research. However, the sensitivity of the method to feature depth itself has not yet been thoroughly investigated. This sensitivity is the first step towards a method capable of measuring the depth of features in addition to detecting them. In this work, the influence of depth on the probe dynamics is investigated using both a linear and nonlinear model and simulation based results of the two are compared. It is argued that a nonlinear approach is essential in estimating the potential performance of subsurface measurements using CRAFM methods.