Differential force microscope

摘要

The present invention is a differential force microscope (DFM) for identifying an individual atom of a substrate, such as a dopant or impurity atom. The DFM includes a light source which can be controlled to turn ON and OFF to cause alternate excitation and relaxation of an atom in the substrate. An atomic force microscope (AFM) includes an electrically conductive tip (AFM tip) positionable adjacent to a surface of the substrate to measure an attractive force or equivalent thereof exerted by the atom on the AFM tip. When the tip is positioned adjacent to the atom, the tip is influenced by attractive forces exerted on the tip by the atom in both the relaxed state and the excited state. A differential amplifier amplifies the attractive forces to produce an output signal corresponding to a differential attractive force exerted by the atom in the relaxed state and the excited state. As the excitation energy of any atom is unique, it is then possible to identify the specific atom and, moreover, to determine a concentration of such an atom in the substrate.