Induced vibration contact detection for minimizing cantilever tip-sample interaction forces in jumping mode atomic force microscopy

Minimizing tip-sample interaction force is crucial for the performance of atomic force microscopes when imaging delicate samples. Conventional methods based on jumping mode such as peak force tapping require a prescribed maximum interaction force to detect tip-sample contact. However, due to the presence of drag forces (in aqueous environments), noises and cantilever dynamics, the minimal detectable peak force can be large. This results in large tip-sample interaction forces and hence sample damage. To minimize this force, we propose a method based on induction of surface or probe vibrations to detect contact between cantilever probe tip and sample substrate. To illustrate the effectiveness of the method, we report experimental results for contact detection on a PS-LDPE-12M polymer sample. A topography tracking control algorithm based on the proposed contact detection scheme is also presented.