Investigation of surface energy states on Si by photoacoustic spectroscopy

The spectral and dynamic characteristics of surface energy states on Si wafers are investigated by photoacoustic (PA) spectroscopy. The PA spectra were measured as a function of the wavelength and modulation frequency of the excitation optical beam by a PA spectrometer. The PA amplitude spectra of Si samples (n-Si wafer, 500 /spl Omega/cm) with various surface qualities were studied at room temperature in the optical energy beam excitation range from 0.7 to 1.5 eV and for various modulation frequencies (10, 40 and 160 Hz). The different PA amplitude spectra of incoming Si wafers and Si wafers with mechanically roughened surfaces, for various modulation frequencies, indicate the energy distribution and the dynamics of the surface electronic states (SES).