Characterization of sputtered ZnO thin film as sensor and actuator for diamond AFM probe

In order to develop a diamond atomic force microscopy (AFM) probe with a piezoelectric sensor and actuator, we fabricated piezoelectric zinc oxide (ZnO) thin film and measured its piezoelectric constant. First, we developed a simple measurement method for the piezoelectric constant of the thin film, d(31). This was based on the free vibration theory of cantilever beams. The values of d(31) were determined by measuring an electric charge induced in the piezoelectric thin film on the vibrating cantilever beam and its displacement. Using this method, we evaluated d(31) for ZnO thin film sputtered at various substrate temperatures. The ZnO thin film deposited at temperatures of less than 350 degreesC was highly c-axis oriented and showed a high piezoelectric constant d(31) of -3.5 pC/N. Using this value, we calculated properties of the diamond cantilever AFM probes of various dimensions and of 5 Am in thickness with a ZnO sensor and actuator of I Am in thickness. The resolution of displacement and actuation force for a probe of 150 Am in length and 50 Am in width were estimated to be about 1.5 nm at a resolution of charge measurement of I X 10(-15) C and 7 AN at an applied voltage of 10 V, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.