Boundary instability of an erosion laser plasma expanding into a background gas

Abstract

PACS 61.43.Dq -Amorphous semiconductors, metals, and alloys PACS 62.50.-p -High-pressure effects in solids and liquids PACS 61.05.C--X-ray diffraction and scattering Abstract -Ge0.15Sb0.85 is a phase change material that undergoes a transition from a semiconducting glass to a crystalline metal when being densified. In this work, we investigate some parameters controlling the crystallization pressure Pc in related compounds by conducting highpressure experiments on initially amorphous, germanium-and silicon-doped antimony. We find that the amorphous phase is stabilized to higher pressures when the dopant size is decreased. This result can be easily rationalized under the assumption that in the glass, Ge and Si atoms occupy tetrahedral or related small coordination shells. When pressure increases, the larger Ge atoms move sooner into the larger octahedral shells, which are characteristic for the crystal, than the smaller Si atoms do. We also find that Pc increases quickly with Ge and Si concentrations. This observation implies that the pressure-induced change of coordination cannot be a local, elementary event, but that the four-coordination of the group-14 atoms is stabilized by the presence of other four-coordinated atoms.

Characteristic properties of laser ablation of translucent targets

“…From the dispersion relation (7), we can also find the maximum increment of the instability growth, i.e. the time, which the amplitude of the boundary perturbation needs to reach the value comparable with the wavelength of the dominant mode:…”

“…After each pulse of radiation, the target was moved. The high-speed shooting of the laser plume was conducted with the help of the photoinstallation VFU-1 (8) with an additional lens (7). For one pulse of laser radiation, 49 consecutive frames could be taken.…”

“…The evolution of hydrodynamic instabilities at the laser crater or their absence is of fundamental importance, both for understanding ablation processes and, in particular, for the production of nanopowders. The instabilities in laser a plume mentioned in for example [1,[6][7][8] can also influence the formation of nanoparticles; however such instabilities are outside the scope of our paper.…”