Interactions of wide band-gap single crystals with 248 nm excimer laser radiation. I: MgO

The emission of charged and neutral particles from single-crystal MgO irradiated with pulsed 248 nm excimer laser light is studied by means of quadrupole mass spectrometry, time-resolved emission spectroscopy, luminescence spectroscopy, and scanning electron microscopy (SEM) observations. The role of the initial distribution of near-surface defects plus defects which result from repeated application of laser pulses is explored. This increase in defect density eventually leads to formation of a visible plume and rapid material vaporization. SEM observations after irradiation indicate that substantial surface fracture is present prior to the onset of rapid vaporization. Defect production during irradiation is attributed to mechanical processes involving deformation and fracture with accompanying dislocation motion. The accumulation of these defects increases laser absorption in the near-surface region resulting in rapid thermal etching and cluster emission.