FORCE-BALANCING MICROFORCE SENSOR WITH AN OPTICAL-FIBER INTERFEROMETER

A microforce sensor with a force feedback method for scanning force mi croscopy is presented. The force sensor is constructed by using an opt ical fiber and a microcantilever. The facet of the optical fiber is co ated with a gold thin film 15 Angstrom thick. This gold film acts not only as a partially reflected mirror but also as an electrode of the e lectrostatic actuator. The interaction force between a probe tip and a sample is balanced by the electrostatic force. The deflection of the cantilever is measured by an interferometer consisting of the facet of the optical fiber and the cantilever surface. We have made the force sensor and measured some force curves of a mica surface with a SIN pro be tip. The force curves obtained by this sensor are quite different f rom the curves by a conventional measurement without a feedback system . The force resolution of the system is 10(-10) N with a bandwidth of dc similar to 1 kHz. (C) 1997 American Institute of Physics.