SOFT LASER SPUTTERING OF INP(100) SURFACE

Laser sputtering of InP(100) surface with 337 nm photons was investiga ted for fluences ranging from the threshold for particle emission up t o about 370 mJ/cm(2). Sputtered atoms and molecules are detected durin g their flight using resonant laser post-ionization and mass spectrome try. From the shot number and the energy dependencies of the sputterin g yield, it is shown that two sputtering regimes exist. For low fluenc e values (<190 mJ/cm(2)), the sputtering results mainly from absorptio n and excitation of defect sites. Conversely, at higher fluences, inte rband transitions in the whole absorption volume lead after relaxation to a process similar to thermal evaporation. This thermal-like proces s induces the preferential emission of phosphorus in the form of atoms and molecules and the quite different velocities of phosphorus and in dium populations which in absence of collisions separate during their flight. The limit between the two regimes might correspond to the poin t where melting of the surface occurs. (C) 1994 American Institute of Physics.