CONTACT IMAGING IN THE ATOMIC-FORCE MICROSCOPE USING A HIGHER-ORDER FLEXURAL MODE COMBINED WITH A NEW SENSOR

Using an atomic force microscope (AFM) with a silicon cantilever parti ally covered with a layer of zinc oxide (ZnO), we have imaged in the c onstant force mode by employing the ZnO as both a sensor and actuator. The cantilever deflection is determined by driving the ZnO at the sec ond mechanical resonance while the tip is in contact with the sample. As the tip-sample force varies, the mechanical boundary condition of t he oscillating cantilever is altered, and the ZnO electrical admittanc e is changed. Constant force is obtained by offsetting the ZnO drive s o that the admittance remains constant. We have also used the ZnO as a n actuator and sensor for imaging in the intermittent contact mode. In both modes, images produced by using the ZnO as a sensor are compared to images acquired with a piezoresistive sensor. (C) 1996 American In stitute of Physics.