Ion-Beam-Induced Atomic Mixing in Ge, Si, and SiGe, Studied by Means of Isotope Multilayer Structures

Abstract

Crystalline and preamorphized isotope multilayers are utilized to investigate the dependence of ion beam mixing in silicon (Si), germanium (Ge), and silicon germanium (SiGe) on the atomic structure of the sample, temperature, ion flux, and electrical doping by the implanted ions. The magnitude of mixing is determined by secondary ion mass spectrometry. Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy, and transmission electron microscopy provide information about the structural state after ion irradiation. Different temperature regimes with characteristic mixing properties are identified. A disparity in atomic mixing of Si and Ge becomes evident while SiGe shows an intermediate behavior. Overall, atomic mixing increases with temperature, and it is stronger in the amorphous than in the crystalline state. Ion-beam-induced mixing in Ge shows no dependence on doping by the implanted ions. In contrast, a doping effect is found in Si at higher temperature. Molecular dynamics simulations clearly show that ion beam mixing in Ge is mainly determined by the thermal spike mechanism. In the case of Si thermal spike, mixing prevails at low temperature whereas ion beam-induced enhanced self-diffusion dominates the atomic mixing at high temperature. The latter process is attributed to highly mobile Si di-interstitials formed under irradiation and during damage annealing.

A new approach to monitor $$^{13}\hbox {C}$$-targets degradation in situ for $$^{13}\hbox {C}(\alpha ,\hbox {n})^{16}\hbox {O}$$ cross-section measurements at LUNA

“…Therefore, high beam currents (hundreds of µA) and long irradiation times (weeks or months) are often necessary to achieve high enough signal-to-noise ratios for a successful cross-section measurement at low energies. Yet, target modification processes (such as diffusion, melting, sputtering or contamination of target surface [5,6]) that occur under intense beam irradiation may result in significant changes of target composition and/or stoichiometry as a function of irradiation depth [7] and an in-situ monitoring of target properties is generally required.…”

Bulk and Short‐Circuit Anion Diffusion in Epitaxial Fe2O3 Films Quantified Using Buried Isotopic Tracer Layers

“…Incorporation of cation or metallic tracers, such as 57 Fe in the iron/iron oxide system, can easily be achieved with MBE. [43][44][45][46] While the availability, cost, and potential radioactive decay of suitable isotopically enriched source material must be considered, it is possible that stacks can incorporate more than one isotope in the buried layer(s); e.g., both cations and anions can be isotopically labeled to probe cation and anion transport concurrently. Likewise, diffusion and transport as a result of a wide variety of stimuli, including surface reactions such as corrosion or reduction, electrochemical processes such as ion intercalation, irradiation, and nanoscale mechanical deformation, can be evaluated with this adaptable approach.…”

“…To obtain more accurate diffusivity data, the isotopic tracer would ideally be positioned at a predefined location within the bulk to eliminate surface exchange effects, and its distribution after diffusion would be characterized at high mass and spatial resolution in 3D to deconvolute lattice and grain boundary diffusion pathways. Recent work has demonstrated the ability to deposit thin-film structures containing isotopically enriched layers by molecular beam epitaxy (MBE) [42][43][44][45][46][47][48] and sputtering. [49,50] Characterization by neutron reflectivity [43,45,49,50] or SIMS [46] of the isotopic distribution in these thin film stacks after annealing provides 1-D diffusivity data in the absence of surface effects, but cannot reveal the lateral distribution of diffusing species to grain boundaries or other defects in the material.…”

“…Recent work has demonstrated the ability to deposit thin-film structures containing isotopically enriched layers by molecular beam epitaxy (MBE) [42][43][44][45][46][47][48] and sputtering. [49,50] Characterization by neutron reflectivity [43,45,49,50] or SIMS [46] of the isotopic distribution in these thin film stacks after annealing provides 1-D diffusivity data in the absence of surface effects, but cannot reveal the lateral distribution of diffusing species to grain boundaries or other defects in the material. To overcome this limitation, information-rich 3D composition maps of the elemental and isotopic distribution in solids can be obtained by atom probe tomography (APT) [51] with excellent areal and depth spatial resolution of <1 nm.…”