Step-scan FT-IR photoacoustic (S-2 FT-IR PA) spectral depth profiling of layered materials

We have demonstrated that step-scan FT-IR photoacousic spectroscopy (S-2 FT-IR PAS) has the advantages of easy extraction of signal phase and of constant probing depth applied to the entire spectrum range. High depth resolution and distinctive discrimination have been achieved by using PA phase information. The PA phase theory for multilayer materials elucidates the qualitative phase analysis rules established earlier with the experimental data and provides very useful instrument-independent phase-difference models. Quantitative determinations of thermal, optical, and geometric parameters of multilayer materials are made possible by applying the phase-difference models to the experimental data of S-2 FT-IR PAS.