EFFECT OF PZT AND PMN ACTUATOR HYSTERESIS AND CREEP ON NANOINDENTATION MEASUREMENTS USING FORCE MICROSCOPY

Nanoindentation measurements performed using the atomic force microscope (AFM) are significantly affected, both with regard to indentation curve shape and quantitative values of the measurements (70% variation in measured modulus), by the well-known effects of hysteresis and creep in the lead zirconate titanate (PZT) piezoceramic actuators used to control the positioning and motion of the mechanical components of the AFM. A capacitance-based displacement calibrator has been built and it was discovered that the response of PZT ceramics may vary (up to 66%) depending upon the conditions under which the piezoceramic is calibrated. By replacing the PZT actuators with lead magnesium niobate (PMN) electrostrictive actuators, nanoindentation measurements have been obtained using the AFM that are both reproducible and quantitative.