Characteristics of plasma scalds in HfO_2/SiO_2 multilayer films are studied. The scalding behaves as surface discoloration under microscope. The shape is nearly circular when the laser incidence angle is close to normal incidence and is elliptical at oblique incidence. The nodular-ejection pit is in the center of scalding region when laser irradiates at the incidence angle close to normal incidence and in the right of the scalding region when laser irradiates from left to right at oblique incidence. The max damage size of scalding increases with laser energy. The edge of scalding is high compared with the unirradiated film surface and the region tending to the center is concave. It belongs to a surface damage. The max depth of a scald increases with its size. Tiny pits of nanometer scale can be seen in the scalding film under scan electronic microscope (SEM) at a higher magnification. Scalds don't grow during further illumination pulses until 65 J/cm~(-2).
展开▼
