Observation of heat pulses scattered from ion bombardment damage at sapphire surfaces

Abstract
The authors have observed large changes in the back scattering of high-frequency phonons (heat pulses) in sapphire at low temperatures following ion bombardment of the reflecting surfaces, including absorption possibility due to amorphous two-level systems. As a means of detecting such damage, the technique appears to be at least as sensitive as Rutherford back channelling, and since it samples the damaged region from the bulk side it provides new data against which to test current models.