Radiation induced nucleation of nanoparticles in silica

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2000-05, Vol.166-167, p.845-850
• Main Authors: Ila, D., Williams, E.K., Zimmerman, R.L., Poker, D.B., Hensley, D.K.
• Format: Article
• Language: English
• Subjects: Ion implantation; Nanocrystals; Optical materials
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(99)00794-6

There is a threshold implantation dose, after which some of the implanted species will tend to spontaneously form nanoclusters, over-dose-implantation. Similarly, there is a threshold implantation dose for the implanted species in a layer of the host material, such that after high temperature annealing the nanoclusters can nucleate before the implanted material can dissolve in the host material (during such heat treatments). In this paper, we present the results of our investigation of producing nanoclusters of gold in silica at fluences of two orders of magnitude less than what is traditionally used. This is accomplished by implanting 2.0 MeV Au into silica followed by MeV bombardment by MeV Si ions. This process was used to reduce the threshold implantation dose by at least two orders of magnitude. To follow the formation of nanoclusters, we used both indirect measurement methods such as optical absorption spectrophotometry (non-destructive), and direct methods such as transmission electron microscopy (destructive). The size of the nanoclusters, ranging from 1 to 10 nm, are controlled by the implantation dose and by the total electronic energy deposited by each post-bombarding ion in the implanted layer. We will show how and at what concentrations species such as gold nucleates to form nanoclusters, either by induced strain or by radiation-enhanced nucleation at a dose below that needed for spontaneous nanocluster formation.