Formation of nanoclusters with varying Pb/Se concentration and distribution after sequential Pb~+ and Se~+ ion implantation into SiO_2

摘要

First results obtained from electron beam annealed sequentially implanted Pb~+ (29 keV) and Se~+ (25 keV) ions into a SiO_2 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 SiO_2 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 ℃, 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 SiO_2 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.