8.1.1.6 Photothermal displacement spectroscopy

This chapter presents a brief discussion of photothermal displacement spectroscopy (PDS). The PDF measures an absorption coefficient by exploiting the thermal expansion of a solid upon light absorption and subsequent non-radiative de-excitation (optical heating). A combination of surface and bulk properties is detected by the PDS. The most important application of PDS to surface science has been the study of cleavage faces of Si and Ge with photon energies below the energy gaps. The equivalence of results obtained with PDS and conventional surface differential reflectivity is demonstrated for the case of Ge(111)2x1.