Repetitive ultrafast melting of InSb as an x-ray timing diagnostic

We have demonstrated the possibility of using repetitive ultrafast melting of InSb as a timing diagnostic in connection with visible-light pump∕x-ray probe measurements at high-repetition-rate x-ray facilities. Although the sample was molten and regrown approximately 1×106 times, a distinct reduction in time-resolved x-ray reflectivity could be observed using a streak camera with a time resolution of 2.5ps. The time-resolved x-ray reflectivity displayed this distinct decrease despite the fact that the average reflectivity of the sample had fallen to approximately 50% of its original value due to accumulated damage from the prolonged laser exposure. The topography of the laser-exposed sample was mapped using an optical microscope, a stylus profilometer, photoelectron microscopy, and a scanning tunneling microscope. Although the surface of the sample is not flat following prolonged exposure at laser fluences above 15mJ∕cm2, the atomic scale structure regrows, and thus, regenerates the sample on a nanosecond...