High Frequency LIMM - A Powerful Tool for Ferroelectric Thin Film Characterization

In this work, the laser intensity modulation method (LIMM) is applied to the investigation of sputtered self-polarized PZT thin films. A previous analytic solution of the LIMM Fredholm integral equation of the first kind by use of the Mellin transform is generalized and limitations of this approach are discussed. The numerically reconstruction of the pyroelectric coefficient profile is based on a eight-layer thermal model. The profile reconstruction was performed using MATLAB software containing algorithms for the inverse solution of the appropriate Fredholm integral equation and a Tikhonov regularization method for stable numerical solutions. Optimized algorithms for thermal parameter determination from the low frequency part of the pyroelectric current spectrum are presented. The impact of thermal parameters on the reconstructed profile was investigated. Monte-Carlo simulations were used for a comparison of different approaches for the regularization parameter estimation.