Ion Beam-induced Quantum Dot Synthesis in Glass
- PDF / 899,401 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 13 Downloads / 189 Views
1020-GG06-01
Ion Beam-induced Quantum Dot Synthesis in Glass Harry Bernas1, and Roch Espiau de LamaÎstre1,2 1 Bat. 108, CSNSM-CNRS, University Paris-Sud 11, Orsay, 91405, France 2 Corning SA, Fontainebleau Research Center, Avon, 77210, France ABSTRACT Irradiation-induced processes are often considered only in their nonequilibrium aspects. The purpose of this brief review is to show that chemistry, and particularly redox properties, play a major role in the thermal evolution of such systems and generally cannot, therefore, be neglected. This is exemplified by the synthesis of Ag nanoclusters in glasses and silica, under both low (gamma-ray) and high (MeV ion) deposited energy density irradiation conditions. The nanocluster formation mechanism is shown to be similar to the latent image formation process in photography. The corresponding information was used to control nucleation and growth of PbS clusters in glasses, leading to promising optical properties. In the course of these studies, we also showed that lognormal size distributions characterize the absence of information on the nanocluster formation process.
INTRODUCTION To what extent do nonequilibrium processes circumvent familiar thermodynamical laws, and allow us to design novel ways of synthesizing nanocrystals in a given host ? This question is necessarily present when attempts are made to expand the range of synthesis techniques beyond the impressive capacities of, say, colloidal chemistry. The latter may provide a large variety of pure or composite (alloy, core-shell) nanocrystals, with very narrow size distributions (typically a few percent), but their major limitation, in some important cases, is the difficulty of inserting the nanocrystals into an appropriate host without modifying (or destroying) them. Hence the efforts to promote synthesis in the desired host, and the subsequent problems of dealing with temperature-dependent solubility, diffusion, and preferential interactions in the case of multicomponent systems. Ion implantation (or irradiation), combined with post-annealing, has been used for many years [1] as a means of both forcing solubility and synthesizing nanocrystals in the glasses and other insulators on which we focus here. As a rule, results thus obtained have been discussed in terms of specific ion-beam interactions such as impurity-defect interactions, ion beam or recoil mixing, etc. Although chemical effects have been evidenced previously, they had not previously been related systematically to charge carrier properties. In this Symposium talk, we review our efforts in this direction, as well as a study of the meaning of lognormal nanocluster size distributions. This work has been described in a series of submitted or published papers (see references) whose main results are very briefly summarized here.
BEAM-INDUCED NANOCRYSTAL NUCLEATION AND GROWTH IN INSULATORS: ROLE OF CHARGE CARRIERS Forcing solubility of, say, a metal element such as Ag in an insulator (e.g., a glass) or a semiconductor by ion implantation results in a compos
Data Loading...
