Several experimental techniques for the nondestructive probing of charge and polarization profiles in thin dielectrics are available. Most of these methods are based either on the diffusion of heat after a thermal excitation or on the propagation of a pressure wave after mechanical excitation. A general response equation for these two families of experimental techniques is derived on the basis of a laboratory coordinate system, in which the relative movement of charges and sample electrodes is considered. Position-independent material parameters are assumed in the one-dimensional model, since unique profiles can otherwise not be determined from the experimental results; piezoelectric and pyroelectric coefficients are, however, treated as variables and may therefore be position dependent. The first-order derivation itself starts from the fact that a mechanically or thermally excited sample may be seen as a current source, since charge movement in an insulating sample always represents a current. Furthermore, because of continuity, the externally detected current equals the internal sample current. It is shown that the direct approach yields the same general response equation as an earlier rudimentary approach and that this equation can be easily adapted to the different experimental situations of the various pressure-wave and thermal-excitation methods.

• Received 21 May 1990

DOI:https://doi.org/10.1103/PhysRevB.42.7317