SOFT LASER SPUTTERING OF INP(100) SURFACE

Laser sputtering of InP(100) surface with 337 nm photons was investigated for fluences ranging from the threshold for particle emission up to about 370 mJ/cm2. Sputtered atoms and molecules are detected during their flight using resonant laser post-ionization and mass spectrometry. From the shot number and the energy dependencies of the sputtering yield, it is shown that two sputtering regimes exist. For low fluence values (<190 mJ/cm 2), the sputtering results mainly from absorption and excitation of defect sites. Conversely, at higher fluences, interband transitions in the whole absorption volume lead after relaxation to a process similar to thermal evaporation. This thermal-like process induces the preferential emission of phosphorus in the form of atoms and molecules and the quite different velocities of phosphorus and indium populations which in absence of collisions separate during their flight. The limit between the two regimes might correspond to the point where melting of the surface occurs. © 1994 American Institute of Physics.