Formation of nanoclusters with varying Pb/Se concentration and distribution after sequential Pb⁺ and Se⁺ ion implantation into SiO₂

First results obtained from electron beam annealed sequentially implanted Pb⁺ (29 keV) and Se ⁺ (25 keV) ions into a SiO₂ matrix are presented. Key results from Rutherford backscattering spectrometry and transmission electron microscopy investigations are: (1) Pb and Se atoms are found to bond in the SiO₂ matrix during implantation, forming into nanoclusters even prior to the annealing step, (2) Pb and Se atoms are both present in the sample after annealing at high temperature (T = 760 °C, t = 45 min) and form into PbSe nanoclusters of varying sizes within the implanted region, and (3) the broader concentration profile of implanted Se creates a number of secondary features throughout the SiO₂ film, including voids and hollow shell Se nanoclusters. A sequential ion implantation approach has several advantages: selected areas of nanocrystals can be formed for integrated circuits, the technique is compatible with present silicon processing technology, and the nanocrystals are embedded in an inert matrix - making them highly durable. In addition, a higher concentration of nanocrystals is possible than with conventional glass melt techniques.