Photoacoustic elastic bending method: Investigation of the surface recombination states

The recombination processes of surface modified Si samples by the PA elastic bending method were investigated. The experimental PA elastic bending signals were measured by using special constructed PA cell (the gas-microphone detection technique with transmission configuration) where the sample is mechanically clamped on the edge. The PA amplitude and phase spectra were measured and analyzed, as a function of the modulation frequency for different surface quality of Si wafer. The samples were the disks of intact wafers of Si with different thicknesses, and discs with mechanically treated surfaces. The experimental results and theoretical analyze showed a strong dependence of the PA elastic bending signal due the recombination processes on the surface defect states. These results show a clear influence of the process of the surface modification on the thermodiffusion, thermoelastic and electronic deformation mechanisms of the PA elastic bending signal.