Laser annealing of epitaxial CaF₂ films on Si

Nanosecond time-resolved reflectivity and transmission changes in CaF2/Si(111) structures were measured to study the phase transitions, surface modification and radiolysis induced by nanosecond ruby laser pulses. The Si lattice heating up to the melting point leads to the nanohills formation on the surface of the structure, the height of which does not exceed 100 nm with the average base diameter of 360 nm and the surface density of 2.10(8)cm(2). The Raman scattering and energy-dispersive X-ray spectroscopy data indicate that the nanohills contain cavities inside them, and they are filled with the gas of Si2F6 molecules. The shell of the nanohills, obviously, consists of calcium oxide.