DETECTION MECHANISM OF AN OPTICAL EVANESCENT FIELD USING A NONCONTACTMODE ATOMIC-FORCE MICROSCOPE WITH A FREQUENCY-MODULATION DETECTION METHOD

By using the noncontact atomic force microscope with a frequency modul ation detection method, the force gradient induced by the optical evan escent field was detected in a high vacuum. We succeeded in measuring the exponential distance dependence of the force gradient induced by t he optical evanescent field. Furthermore, we investigated the incident beam intensity and bias voltage dependence of the force gradient indu ced by the optical evanescent field. We confirmed that the detection m echanism is not photothermal effect but the surface photovoltage effec t. (C) 1997 American Vacuum Society.