Nanocluster Formation within the Vapor Plume, Produced by Nanosecond-Laser Ablation: Effect of Initial Density and Pressure Distributions

Abstract

The condensation of vapor in the expanding plume produced by ns-laser ablation is discussed within the framework of the Zeldovich and Raizer theory of condensation. The spherical plume expansion is described by a numerical solution of the hydrodynamic equations by the cubic interpolated pseudo-particle (CIP) method. This permits us to analyze the role of initial distributions of density and pressure on the size distribution function of nanoclusters. For parabolic distributions (for the plume expansion into vacuum), calculations reproduce the same results as those obtained by particular solutions of gas-dynamic equations. When initial distributions deviate from the parabolic distributions, the size distribution function varies. For the rectangular plume, the size distribution function of nanoclusters demonstrates two maximums. A similar effect is observed due to the ambient gas influence.

Formation of nanoscale fine-structured silicon by pulsed laser ablation in hydrogen background gas

“…Results of work on LIF and ReD-LIF show that nanosized particles appear near the center of the plume at about 200 s. 23 The ejected Si atoms disappear at the time when the nanoparticles begin to grow. 17 The disappearance of Si atoms suggests that almost all of the Si atoms in the plume are consumed in forming of Si nanocrystallites.…”

“…20,21 The morphology of the sample is determined by the aggregation and depends on the background gas pressure. Although the nanocrystallization process has been discussed by a number of authors, 12,[17][18][19]22,23 the aggregation mechanism has, as yet, not been taken into account. Since the aggregation takes place after the formation of nanocrystallites, an understanding of the temporal and spatial effects on both nanocrystallization and aggregation is necessary to clarify full picture of the PLA process.…”

Laser Ablation

“…The size of particles is determined by the cooling time and the density of the vapor plume. Currently, numerous groups study particle formation mechanisms because of their influence for ICP-MS and nanotechnology applications [53][54][55][56][57][58][59][60]. For LIBS, the particles represent a loss of signal.…”

Energy balance of a laser ablation plume expanding in a background gas

“…It is not included in the PM-model, and also for other models the predictions are not accurate around the stopping distance [9,16]. In the late stage, the diffusion of particles out of the plume volume becomes gradually more important [4,5,7,11,17].…”

“…Even though these techniques have been applied extensively for a number of years, there is no complete picture of the dynamics of a laser ablation plume in a background gas. PLD of a film by nanosecond lasers is an extremely complex process, which runs through several stages from ini-tial laser irradiation of a solid target, material ejection and transfer through vacuum or a background gas to a substrate [3][4][5]. A more comprehensive knowledge of plume dynamics in a background gas is clearly desirable, in particular because most of the existing treatments are limited to one or two target materials into a single background gas [6][7][8][9].…”