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For many years, Si1−yGey alloys have been applied in the semiconductor industry due to the ability to adjust the performance of Si-based nanoelectronic devices. Following this alloying approach of group-IV semiconductors, adding tin (Sn) into the alloy appears as the obvious next step, which leads to additional possibilities for tailoring the material properties. Adding Sn enables effective bandgap and strain engineering and can improve the carrier mobilities, which makes Si1−x−yGeySnx alloys promising candidates for future opto- and nanoelectronics applications. The bottom-up approach for epitaxial growth of Si1−x−yGeySnx, e.g., by chemical vapor deposition and molecular beam epitaxy, allows tuning the material properties in the growth direction only; the realization of local material modifications to generate lateral heterostructures with such a bottom-up approach is extremely elaborate, since it would require the use of lithography, etching, and either selective epitaxy or epitaxy and chemical–mechanical polishing, giving rise to interface issues, non-planar substrates, etc. This article shows the possibility of fabricating Si1−x−yGeySnx alloys by Sn ion beam implantation into Si1−yGey layers followed by millisecond-range flash lamp annealing (FLA). The materials are investigated by Rutherford backscattering spectrometry, micro-Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. The fabrication approach was adapted to ultra-thin Si1−yGey layers on silicon-on-insulator substrates. The results show the fabrication of single-crystalline Si1−x−yGeySnx with up to 2.3 at. % incorporated Sn without any indication of Sn segregation after recrystallization via FLA. Finally, we exhibit the possibility of implanting Sn locally in ultra-thin Si1−yGey films by masking unstructured regions on the chip, thus demonstrating the realization of vertical as well as lateral Si1−x−yGeySnx heterostructures by Sn ion implantation and flash lamp annealing. [ABSTRACT FROM AUTHOR]

Ge1−xSnx and Si1−x−yGeySnx alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective bandgap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the complementary metal-oxide-semiconductor technology. Unfortunately, the equilibrium solid solubility of Sn in Si1−xGex is less than 1% and the pseudomorphic growth of Si1−x−yGeySnx on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post-growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, x-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall-effect measurements. It is shown that after annealing, the material is single-crystalline with improved crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4 × 1019 cm−3. [ABSTRACT FROM AUTHOR]

We grow AlN/4H-SiC and AlN/6H-SiC heterostructures by physical vapor deposition and characterize the heterointerface with micro-scale resolution. We investigate the spatial stress and strain distribution in these heterostructures using confocal Raman spectroscopy. We measure the spectral shifts of various vibrational Raman modes across the heterointerface and along the entire depth of the 4H- and 6H-SiC layers. Using the earlier experimental prediction for the phonon-deformation potential constants, we determine the stress tensor components in SiC as a function of the distance from the AlN/SiC heterointerface. Despite the fact that the lattice parameter of SiC is smaller than that of AlN, the SiC layers are compressively strained at the heterointerface. This counterintuitive behavior is explained by different coefficients of thermal expansion of SiC and AlN when the heterostructures are cooled from growth to room temperature. The compressive stress values are maximum at the heterointerface, approaching 1 GPa, and relax to the equilibrium value on the scale of several tens of micrometers from the heterointerface. [ABSTRACT FROM AUTHOR]

The flexibility of amorphous anodized alumina (AAO) in developing radiation dosimeter for hadron therapy is reported by controlled carbon ion implantation, followed by thermoluminescence (TL) measurements. The efficacy of amorphous AAO in controlling TL sensitivity is found to be governed by an increase in F+ defect centers as a function of carbon concentration, as revealed from the close resemblance of the trend in photoluminescence intensity. Moreover, its nanoporous structure is demonstrated to be advantageous for defect engineering due to the increase in the surface-to-volume ratio. Detailed X-ray photoelectron spectroscopy analysis suggests the formation of F+ centers by substituting Al3+ ions with C2+ in the vicinity of oxygen vacancies, where depth-dependent study showed the evolution of conducting channels owing to sp2 hybridized C–C bonding, leading to a differential charging effect. This work provides a direction to tune nanoporous AAO in its amorphous form for future ion beam dosimetry. [ABSTRACT FROM AUTHOR]

Amorphous, polycrystalline anatase and epitaxial anatase TiO2 films have been implanted with 5 at. % Co2+. The magnetic and structural properties of different microstructures of TiO2:Co, along with the local coordination of the implanted Co atoms within the host lattice are investigated. In amorphous TiO2:Co film, Co atoms are in the (II) oxidation state with a complex coordination and exhibit a paramagnetic response. However, for the TiO2:Co epitaxial and polycrystalline anatase films, Co atoms have a distorted octahedral (II) oxygen coordination assigned to a substitutional environment with traces of metallic Co clusters, which gives a rise to a superparamagnetic behavior. Despite the incorporation of the implanted atoms into the host lattice, high temperature ferromagnetism is absent in the films. On the other hand, it is found that the concentration and size of the implantation-induced nanoclusters and the magnetic properties of TiO2:Co films have a strong dependency on the initial microstructure of TiO2. Consequently, metallic nanocluster formation within ion implantation prepared transition metal doped TiO2 can be suppressed by tuning the film microstructure. [ABSTRACT FROM AUTHOR]

The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds. [ABSTRACT FROM AUTHOR]

We report the influence of static mechanical deformation on the zero-field spin splitting of silicon vacancies in silicon carbide at room temperature. We use AlN/6H-SiC heterostructures deformed by growth conditions and monitor the stress distribution as a function of distance from the heterointerface with spatially resolved confocal Raman spectroscopy. The zero-field spin splitting of the V1/V3 and V2 centers in 6H-SiC, measured by optically detected magnetic resonance, reveals significant changes at the heterointerface compared to the bulk value. This approach allows unambiguous determination of the spin-deformation interaction constant, which is 0.75 GHz/strain for the V1/V3 centers and 0.5 GHz/strain for the V2 centers. Provided piezoelectricity of AlN, our results offer a strategy to realize fine tuning of spin transition energies in SiC by deformation. [ABSTRACT FROM AUTHOR]

The influence of SiO2 and SiNx cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. The annealing temperature determines the layer microstructure and the cover layers influence the obtained Ga profile. Rapid thermal annealing at temperatures up to 750°C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20?ms flash lamp annealing, a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900°C. However, in this case, Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at. %. The Ga-rich areas are capped with SiOx grown during annealing which only can be avoided by the usage of SiNx cover layers. [ABSTRACT FROM AUTHOR]

We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe+ ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1×1017 and 5×1017 ions cm-2 exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe3Si) close to the surface into a Si-rich silicide (FeSi2) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr+ ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation. [ABSTRACT FROM AUTHOR]

Higher conversion efficiencies while reducing costs at the same time is the ultimate goal driving the advancement of solar cell development. In this work, solar cell emitters are formed in Si substrates by plasma immersion ion implantation (PIII) of phosphine and posterior millisecond-range flash lamp annealing (FLA). In Si-based solar cells, hydrogen plays a fundamental role due to its excellent passivation properties. The optical and electrical properties of the fabricated emitters will be studied, with particular interest in their dependence on the hydrogen content present in the samples. The influence of different FLA annealing parameters and a comparison with traditional thermal treatments such as rapid thermal annealing (RTA) and furnace annealing (FA) will be presented. The samples treated by FLA at 1200 °C for 20 ms in forming gas show sheet resistance values of the order of 60 Ω/⇔, and minority carrier diffusion lengths in the range of ~200 µm without the use of a capping layer for surface passivation. Those results are significantly better than the ones observed from RTA or FA annealed samples. The simultaneous implantation of hydrogen during the doping process, combined with optimal FLA annealing parameters, gave promising results for the application of this technology in replacing the conventional POCl3 deposition and diffusion. [ABSTRACT FROM AUTHOR]

Analyzing pole figures obtained by x-ray diffraction experiments, quantitative texture analyses are carried out on 50 nm thick Cu films sputter-deposited on oxidized Si substrates and on Ta-Si-N diffusion barrier films of various compositions. To explain the observed Cu texture formation during layer deposition, a model of two-dimensional grain growth in thin films is applied. In the case of silicon oxide substrates, a <111> Cu fiber texture component resulting from the minimization of the surface and interface energy is observed, in addition to a <100> component resulting from the minimization of the strain energy. For Cu films deposited onto Ta-Si-N diffusion barriers, preferred growth occurs only for <111>-oriented Cu grains and their twins. The volume fractions of both components decrease with increasing N content of the diffusion barrier. Annealing of the Cu films at Tan=600 °C results in a strengthening and a sharpening of the <111> component. Hence, both the chemical composition of the underlayer as well as a postdeposition anneal are observed to have a significant impact on the texture of thin Cu films. [ABSTRACT FROM AUTHOR]

A model Hamiltonian approach to chemisorption is described which is a development of the model described previously for the cases of larger overlaps SA between metal wave functions and adorbitals. Inconsistencies due to basis set overcompleteness are cured. Nonorthogonality between adsorbate projected metal wave functions on different adorbitals is accounted for by explicitly evaluating the overlap integrals between them as well as the hopping terms in the metal part of the Hamiltonian due to coupling of metal wave functions through the adorbitals. Physically adequate hopping between adatom and metal through the core potentials is introduced for high overlap situations. The core hopping terms merge smoothly into the Wolfsberg–Helmholz approximation to core hopping, established earlier to lead to a reasonable description of chemisorption interactions at small overlaps. For the limiting case SA =1, due to completeness of the metal basis set, the adorbitals will be represented by the metal wave functions. k–k state scattering between metal electrons in the overlap region is introduced explictly. Electron repulsions between metal electrons in the overlap region are estimated subject to conditions of hybridizational and rotational invariance and requirements imposed by overcompleteness. The model Hamiltonian is applied to Li adsorption on the (100) surface of copper. The numerical results obtained are discussed extensively and compared to other theoretical work and to experiment. [ABSTRACT FROM AUTHOR]

Mono-energetic cobalt implantation into hydrogenated diamond-like carbon at room temperature results in a bimodal distribution of implanted atoms without any thermal treatment. The ∼100 nm thin films were synthesised by mass selective ion beam deposition. The films were implanted with cobalt at an energy of 30 keV and an ion current density of ∼5 μA cm−2. Simulations suggest the implantation profile to be single Gaussian with a projected range of ∼37 nm. High resolution Rutherford backscattering measurements reveal that a bimodal distribution evolves from a single near-Gaussian distribution as the fluence increases from 1.2 to 7 × 1016 cm−2. Cross-sectional transmission electron microscopy further reveals that the implanted atoms cluster into nanoparticles. At high implantation doses, the nanoparticles assemble primarily in two bands: one near the surface with nanoparticle diameters of up to 5 nm and the other beyond the projected range with ∼2 nm nanoparticles. The bimodal distribution along with the nanoparticle formation is explained with diffusion enhanced by energy deposited during collision cascades, relaxation of thermal spikes, and defects formed during ion implantation. This unique distribution of magnetic nanoparticles with the bimodal size and range is of significant interest to magnetic semiconductor and sensor applications. [ABSTRACT FROM AUTHOR]

An all-electrical method is presented to determine the exchange constant of magnetic thin films using ferromagnetic resonance. For films of 20 nm thickness and below, the determination of the exchange constant A, a fundamental magnetic quantity, is anything but straightforward. Among others, the most common methods are based on the characterization of perpendicular standing spin-waves. These approaches are however challenging, due to (i) very high energies and (ii) rather small intensities in this thickness regime. In the presented approach, surface patterning is applied to a permalloy (Ni80Fe20) film and a Co2Fe0.4Mn0.6Si Heusler compound. Acting as a magnonic crystal, such structures enable the coupling of backward volume spin-waves to the uniform mode. Subsequent ferromagnetic resonance measurements give access to the spin-wave spectra free of unquantifiable parameters and, thus, to the exchange constant A with high accuracy. [ABSTRACT FROM AUTHOR]

A correction to the article about a morphology study of spinodally decomposed silicon-rich oxide that was published online on September 25, 2013 is presented.

Sponge-like Si nanostructures embedded in SiO2 were fabricated by spinodal decomposition of sputter-deposited silicon-rich oxide with a stoichiometry close to that of silicon monoxide. After thermal treatment a mean feature size of about 3 nm was found in the phase-separated structure. The structure of the Si-SiO2 nanocomposite was investigated by energy-filtered transmission electron microscopy (EFTEM), EFTEM tomography, and atom probe tomography, which revealed a percolated Si morphology. It was shown that the percolation of the Si network in 3D can also be proven on the basis of 2D EFTEM images by comparison with 3D kinetic Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

We explore the nature of the metal-insulator transition in the two-dimensional organic compound β ″ -(BEDT-TTF) 2 Hg(SCN) 2 Cl by x-ray, electrical transport, ESR, Raman, and infrared investigations. Magnetic and vibrational spectroscopy concurrently reveal a gradual dimerization along the stacking direction (a-b), setting in already at the crossover temperature of 150 K from the metallic to the insulating state. A spin gap of Δ σ =47 meV is extracted. From the activated resistivity behavior below T = 55 K, a charge gap of Δ ρ =60 meV is derived. At T CO = 72 K, the C=C vibrational modes reveal the development of a charge-ordered state with a charge disproportionation of 2δ ρ =0.34e. In addition to a slight structural dimerization, charge-order causes stripes most likely perpendicular to the stacks.