Piezoresponse force spectroscopy (PFS) has emerged as a powerful technique for probing highly localized polarization switching in ferroelectric materials. The application of a dc bias to a scanning probe microscope tip in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the tip, detected though the change of local electromechanical response. Here, we analyze the signal formation mechanism in PFS by deriving the main parameters of domain nucleation in a semi-infinite ferroelectric semiconductor material. The effect of surface screening and finite Debye length on the switching behavior is established. We predict that critical domain sizes and activation barrier in piezoresponse force microscopy (PFM) is controlled by the screening mechanisms. The relationships between domain parameters and PFM signal is established using a linear Green's function theory. This analysis allows PFS to be extended to address phenomena such as domain nucleation in the vicinity of defects and local switching centers in ferroelectrics. (c) 2007 American Institute of Physics.
