2, University of Connecticut, Storrs, Connecticut, United States
The advent of nanoelectromechanical systems is leading to the requirement to quantitatively measure the piezeoelectric coefficients of thin films on a small spatial scale. This paper contrasts the use of three different approaches for local measurements: spatially mapped interferometry measurements, nanobeam synchrotron diffraction measurements, and piezoresponse force microscopy. A single beam laser interferometer based on a modified Mirau detection scheme with a vertical resolution of about 5 pm was developed for localized d33,f measurements on patterned piezoelectric films. The tool provides high spatial resolution (~ 2 microns), essential for understanding scaling and processing effects in piezoelectric materials. This method can capture both intrinsic and extrinsic contributions to the displacement, and has excellent accuracy providing flexure-induced artifacts associated with contact structures are avoided. Nanobeam synchrotron diffraction measurements have been used to map the local piezoelectric response of patterned arm structures in lead magnesium niobate - lead titanate thin films. In this case, the lateral resolution is constrained by the X-ray optics: in this case a full width at half maximum of 250 nm; typically however, only the intrinsic response is probed, unless stroboscopic techniques are employed. These results are compared quantitiavely with measurements from piezoresponse force microscopy, in which better spatial resolution is achieved, but at the expense of absolute d33,f values.