Diffusion properties of chalcogens (S, Se, Te) into pure silica
ABSTRACT The diffusion properties of chalcogens (S, Se, Te) implanted into SiO2 were studied via secondary ion mass spectroscopy (SIMS) profiling between room temperature and the glass transition temperature (800–950 °C). Annealing of Te-containing samples leads directly to precipitation of metallic tellurium nanocrystals within the implantation profile. The S and Se concentration profiles were fitted by using a simple diffusion model in order to provide estimates of the diffusion constant and approximate solubility of these fast moving chemical species. A comparison of their differing diffusion behavior with complementary data on these systems suggests that (i) their oxidation states play a crucial role and (ii) the chalcogen propagation mechanism actually involves complex chemical interactions.
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ABSTRACT: Metallic or semiconductor nanocrystals produced by very different techniques often display size distributions whose limiting shape (e.g., after long annealing times) is self-preserving and close to lognormal. We briefly survey the diverse microscopic mechanisms leading to this behavior, and present an experimental study of its inception in the case of semiconducting nanocrystals synthesized by ion implantation in silica. This example shows how the ultimate lognormal distribution is related to the system’s memory loss of initial nucleation and growth processes.Physical Review B 03/2006; 73(12). DOI:10.1103/PhysRevB.73.125317 · 3.66 Impact Factor
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ABSTRACT: First results obtained from electron beam annealed sequentially implanted Pb+ (29keV) and Se+ (25keV) 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=45min) 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.Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 02/2012; DOI:10.1016/j.nimb.2011.07.075 · 1.19 Impact Factor
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ABSTRACT: In latter years, many studies of ion beam-induced nanocluster (NC) formation in insulators have focussed on the effects of the ion beam interaction itself: defect formation, ion beam mixing, radiation-enhanced diffusion, etc. In a recent series of papers, we have taken an alternative approach that emphasizes the consequences of the beam's energy deposition as regards charge formation (electron, holes; defects as charge reservoirs; host and impurity atom ionization..) in matter. This leads to a parallel between photon and charged particle irradiations, and involves studies of the physicochemical, as well as the `purely physical' effects of energy deposition.Radiation Effects and Defects in Solids 07/2007; 162(7):573-574. DOI:10.1080/10420150701475505 · 0.60 Impact Factor