Secondary ion emission dynamics model

Abstract:

Nuclear tracks produced in solids by fast projectiles are the result of processes such as ionization,^-electron energy deposition and induced chemical reactions. Several techniques have been used to analyze the different characteristics of the tracks, eg, AFM, sputtering yield and Auger emission measurements. In this work, it is discussed the suitability of the secondary ion emission dynamics, particularly the initial velocity distribution and angular distribution analyses, as a tool to study the track formation processes occurring in the picosecond time range. The choice of the secondary ion for analysis selects a particular surface area and a desorption time range of interest: a) H+ is emitted within few picoseconds after impact time and from the impact site surface, b) H-desorption occurs one order of magnitude later and from the impact periphery, c) heavy atomic or molecular ions are also emitted later and from periphery, but pushed away by pressure pulses coming from the track. As the secondary ion dynamics depends on the track electric field, the ion trajectories and energy distributions are directly connected with the production, position or movement of the secondary electrons inside the dielectric. Therefore, quantities such as radius of the positive inner track (which is assumed to be larger than the so called infratrack) and the (time-dependent) track charge density can be determined by modeling experimental data obtained by time-of-flight technique.

Año de publicación:

2006

Keywords:

Fuente:

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