Using laser induced surface acoustic waves to characterize thin films and material surfaces

The test method LAwave (R) measures the dispersion of surface acoustic waves induced by short laser pulses. The technique uses that the propagation velocity of the wave depends on the frequency in coated and surface modified materials. Measuring the dispersion of the surface acoustic wave enables to determine important properties of the material surface. Two examples demonstrate that the laser-acoustic method can solve very different problems of surface engineering. The wear resistance of diamond-like carbon films with a thickness of few nano-meters was evaluated. The depth of sub-surface damage layers in semi-conductor materials was determined, which are created when wafers are sliced from the ingot.