The size distribution of Si nanoparticles prepared by pulsed-laser ablation in pure He, Ar or Ne gas

Abstract

Nanocrystalline silicon films were prepared by pulsed-laser ablation in high-purity He, Ar or Ne gas at room temperature under a deposition pressure of 10 Pa. The Raman and Xray diffraction spectra indicate that the films are nanocrystalline. Scanning electron microscopy images show that Ar or Ne gas, compared to He gas, yields smaller and more uniform-sized Si nanoparticles at the same deposition conditions, which is also confirmed by the blue-shifted and narrower peaks obtained in photoluminescence measurement. Ne gas induces the smallest and most uniform, in size, Si nanoparticles among all the three gases, which may be attributed to a more effective energy transfer between Si and Ne atoms resulting from the adjacent degree of the atomic weights.

Influence of laser beam on transport dynamics of Si nanoparticles by laser ablation

“…Si nanoparticles, being formed between target and substrate, are transported to the substrate and adsorbed on the substrate. In terms of the nucleation area model [7] , Si nanoparticles were formed in a certain range, called nucleation area. The nucleation was a process of gas phase in the PLD, it is depended on the temperature of Si atoms .…”

“…The experimental setup is similar to that used in the previous experiments [7] . Briefly, in pure Ar gas under ambient pressure of 10 Pa, a Lambda Physik XeCl excimer laser (wavelength 308 nm, pulse duration 15 ns, repetition rate 3 Hz)…”

“…We systematically investigated the size dependence and distribution of Si nanoparticles prepared in a high-purity gas of He, Ar or Ne, and "nucleation area" model [7] was proposed to explain the experiment result. According to this model, the narrower "nucleation area" can induce the smaller and more uniform nanoparticles.…”

“…The characteristics of synthesized particles largely depend on fabrication conditions such as the distance between an ablated target and a collecting substrate, the ambient gas, the pressure of the ambient gas, and so on. In order to optimize and control the synthesis process, detailed information on where and when the particles are formed in the ablation plume and how they are transported onto the substrate is required [6] .We systematically investigated the size dependence and distribution of Si nanoparticles prepared in a high-purity gas of He, Ar or Ne, and "nucleation area" model [7] was proposed to explain the experiment result. According to this model, the narrower "nucleation area" can induce the smaller and more uniform nanoparticles.…”

Nucleation and growth of nanoparticles during pulsed laser deposition in an ambient gas

“…This idea can be extended to the nucleation and growth of nanoscale structures with other configurations in various preparation methods. To explain the experimental result that Ne gas induces the smallest and most uniform Si nanoparticles (np-Sis, i.e., Si nanograins, nanocrystals, nanoclusters or quantum dots) among He, Ar, and Ne, we proposed a qualitative model (Fu et al, 2005), which indicated that for ns-PLD, there are three regions, labeled "high energy region," "nucleation region" (NR), and "transporting region." The mean size and size-consistency of np-Sis depend on the width of NR where the nucleation and growth occur.…”