Texture of GaAs Nanoparticles Deposited by Pulsed Laser Ablation in Different Atmospheres

This work analyzes the effect of nanosecond laser pulse deposition of GaAs in an inert atmosphere of Ar and He. The number of pulses and the gas pressure were varied and the effect on the nanoparticles formation was studied by scanning electron microscopy, grazing incidence small angle X-ray scattering, and atomic force microscopy. It is shown that the GaAs nanoparticle sizes and size distributions can be controlled partly by the number of laser pulses applied during their production and partly by the choice of inert gas and its pressure. Our results suggest that He is a more promising working gas producing narrower size distributions and a better size control of the grown nanoparticles. 1. Introduction Pulsed laser deposition (PLD) is a simple and convenient method of producing various types of materials among which are also nanoscaled materials [1]. In such materials the quantum confinement becomes a dominant effect and it significantly modifies their properties. PLD using very short pulses is particularly interesting for the deposition of complex multielement films, preserving the stoichiometry of the parent materials [2]. Numerous experiments were carried out and rich scientific information of the ablation process was obtained. Nevertheless, several mechanisms involved in these processes are not yet completely understood. Different results cause continuing discussion about ultrafast melting [3], resolidification dynamics [4], surface structure modification [5], thermal and nonthermal mechanisms of ablation [6], and direct cluster emission. This is the reason for the continuation of extensive studies, both theoretical and experimental, on the dynamics of laser heating, melting, resolidification, and ablation of the target material irradiated by different pulse durations and wavelengths. The effects of the background gas on the deposition process were considered in a number of papers [7]. The experimental results on ablation in the presence of ambient gas revealed the importance of the ambience gas parameters, though some of them are not of chemical nature. Previous results [8] show that the effect of the background gas depends on the combination of the ambient and laser parameters used in the PLD. In the PLD process, the nature of the phenomena taking place during the plasma expansion depends upon the gas pressure in the ablation chamber [9]. Under low pressure, from vacuum up to 0.5？mbar, atoms and ions are solely present in the plume leading to film formation and growth. At intermediate gas pressure, 1–20？mbar, the emitted species undergo