Photoacoustic Analysis of Illuminated Si-TiO2 Sample Bending Along the Heat-Flow Axes

This paper describes the influence of thin transparent film on thermal and elastic characteristics of the two-layer sample consisting of the silicon substrate and thin TiO2 film using analysis of photoacoustic signals and their components in the 20 Hz - 20 kHz frequency domain. Through thermoelastic component changes, it was found that the thin film significantly changes the thermal state of the substrate and makes the degree of its bending increase drastically. The relationships between the thermoelastic component, the displacement along the heat flux axis and the difference of carrier density and temperatures on the different sides of the sample are described. It has been shown that the addition of a thin transparent film to a silicon substrate can effectively reduce the influence of photogenerated carriers in the substrate, especially on its degree of flexibility and restore it efficiently.