A Novel Highly Integrated SPM System for Single Molecule Studies

The design and performance of a highly integrated scanning probe microscopy for single molecule studies is presented. The new approach realized tunable contact strength, stretching dynamics as well as electric potentials, which make it possible to tune and measure the single molecule electromechanic properties. The tunable contact strength is realized by a dual-feedback loop-controlled tip engagement with automatic mode switching. Electric current and stretching force of the molecular junctions are monitored simultaneously. In case of no current during the engage process, the system will automatically switch to traditional atomic force microscope force-feedback to protect the tip from crashing. The stretching dynamics is tuned by adapting programmable stretching behaviors. Tip-sample bias can also be swept when molecules are bridged in the break junctions. Applications of this system to octanedithiol (C8) molecules are also demonstrated.