Aging effects on the nucleation of Pb nanoparticles in silica

Abstract

The ion beam synthesis of Pb nanoparticles (NPs) in silica is studied in terms of a two step thermal annealing process consisting of a low temperature long time aging treatment followed by a high temperature short time one. The samples are investigated by Rutherford backscattering spectrometry and transmission electron microscopy. The results obtained show that highly stable Pb trapping structures are formed during the aging treatment. These structures only dissociate at high temperatures, inhibiting the nucleation of NPs in the metallic phase and causing an atomic redistribution that renders the exclusive formation of a two dimensional, uniform and dense array of Pb NPs at the silica–silicon interface. The results are discussed on the basis of classic thermodynamic concepts.

Tuning of the size and the lattice parameter of ion-beam synthesized Pb nanoparticles embedded in Si

“…The peak positions of Pb (1 1 1) are the same as the ones of Si (1 1 1), indicating a cube-on-cube epitaxial relationship between the Pb NPs and the Si matrix. Therefore, we can conclude that the fcc-Pb NPs are crystallographically oriented with respect to the Si matrix according to Pb Formation of Pb NPs growing in parallel alignment with the Si matrix after implantation and subsequent annealing is in good agreement with earlier observations [20,41,42], where TEM was used to verify the existence of aligned Pb NPs. In addition, the hexagonal shape of the Pb NP perpendicular to the Si [0 1 1] zone axis (figure 7(a)) indicates that the particle shape is a truncated octahedron bounded by {1 1 1} and {0 0 1} planes.…”

Interplay of ballistic and chemical effects in the formation of structural defects for Sn and Pb implanted silica

“…Previous studies of Pb implanted SiO 2 have found (before thermal annealing) Pb clusters [9,10] as well as Pb\O interactions [10]. Note that both of these studies used a much higher implantation energy (~300 keV) than the current study (30 keV) which leads to ion depths of~100 nm rather than the~20 nm here.…”

“…While one likely would not see such strong spectral weight from Pb\O bonding in the SiO 2 :Pb due to the lower relative concentration of Pb, it provides an indication of the type of feature one would expect to see. Thus, it is evident that in this case the Pb ions interact minimally with the O atoms of the host SiO 2 (either through the formation of oxide clusters or as single substitutional or interstitial atoms), and instead they likely aggregate into metallic clusters, as found in previous studies [9,10]. The gradual onset in the pre-edge of the SiO 2 :Pb XAS spectrum could be due to interactions between the surfaces of the Pb clusters and the O atoms of the SiO 2 , or simply due to damage in the SiO 2 .…”

“…Note that both of these studies used a much higher implantation energy (~300 keV) than the current study (30 keV) which leads to ion depths of~100 nm rather than the~20 nm here. In these studies, Pb clusters formed preferentially under lower fluences (entirely Pb clusters at 5 ×10 15 cm −2 for [9] and increasing Pb\O contributions as fluence was increased from 1 to 6 × 10 16 cm −2 in [10]). The explanation for the increasing Pb\O interactions in [10] was suggested to be the increased damage as the fluence was increased.…”

“…SiO 2 implanted with Sn [6][7][8] and Pb [9,10] has shown promise in past studies regarding the formation of metallic or oxide nanoclusters and subsequent non-linear optical properties and Coulomb blockade effects. A combination of X-ray absorption (XAS) and emission (XES) spectroscopy is used in the present work to closely study the structural and chemical effects of implantation.…”