Luminescence of ion-irradiated α-quartz
TL;DR: In this article, a survey of cathode-luminescence spectroscopy performed after ion implantation in α-quartz is presented, in connection with dynamic, laser-induced and chemical epitaxy of the surface layers amorphized during the ion irradiation.
Abstract: Optical functionality of materials used in devices is the basis of modern photonics. It depends on selected photoactive impurities or low-dimensional structures, which can be tailored by ion implantation. The present survey covers cathode-luminescence spectroscopy performed after Ge, Ba, Na, Rb and Cs ion implantation in α-quartz, in connection with dynamic, laser-induced and chemical epitaxy of the surface layers amorphized during the ion irradiation. The correlations, which emerged for various luminescence bands, ion species and thermal processing methods, allows one to classify the bands into ion-specific and intrinsic ones. The microstructural properties measured by ion beam analysis and transmission electron microscopy will be combined with the luminescence data, and the role of photoactive defects in quartz and nanoparticles of the implants will be discussed. The technologically most attractive case of double Rb/Ge implantation will be highlighted, which combines the achievement of full chemical epi...
Citations
More filters
TL;DR: In this article, the authors consider the extensive experimental and computer simulation studies that have been performed over the past several decades on what the nature of the primary damage is, and provide alternatives to the current international standard for quantifying this energetic particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model for metals.
334 citations
Cites background from "Luminescence of ion-irradiated α-qu..."
...For instance, as a single broken bond in a covalently bonded material can be considered a defect [249], the concept of atom displacements as the source of damage does not necessarily apply, and hence the use of the dpa concept is not very well motivated....
[...]
...crystalline materials (quartz in the case of silica) [249,250]....
[...]
TL;DR: In this article, by means of molecular dynamics atomistic models, small nc-Si embedded into defect-free silicon chips are constructed using two different classical interatomic potentials, allowing analysis of the defects at the interface which may serve as radiative and nonradiative recombination centers for excitons formed in nc's and, thus, be responsible for the optical properties of the structure.
Abstract: An efficient means to obtain light emission from a silicon-based material would enable integrating both optical and electronic functionalities on the same silicon chips. The long radiative lifetimes have until recently obstructed efficient light emission from Si. A nanocrystalline approach has opened up a prospect for silicon in the optoelectronics application field. However, the structure of the nanocrystal-matrix interface, which appears to be important for the light emission, remains unclear. In the present work, by means of molecular dynamics atomistic models, small nc-Si embedded into defect-free $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2}$ are constructed using two different classical interatomic potentials. The models allow analysis of the defects at the interface which may serve as radiative and nonradiative recombination centers for excitons formed in nc's and, thus, be responsible for the optical properties of the structure. We analyzed the interface structures after a series of high-temperature annealing runs and subsequent relaxation at room temperature. The results show that the $\mathrm{nc}\text{\ensuremath{-}}\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_{2}$ interface is organized by means of a thin suboxide layer $(\mathrm{Si}{\mathrm{O}}_{2\ensuremath{-}x})$, which contains a considerable amount of undercoordinated defects as well. We also observed the spontaneous formation of silanone bonds $(\mathrm{Si}\mathrm{O})$, frequently discussed in the literature to be centers with an important role on the optical properties of the nc structures.
73 citations
01 Sep 2012-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the authors describe how to extend the effects of lifetime resolution; to detect phase transitions, both stable and transient; and the opportunities which arise from combining the ion beam induced luminescence signals with simultaneous excitation of the materials with photons, electrons or X-rays.
Abstract: Luminescence excited during ion beam bombardment offers information on both stable and metastable defect and impurity sites, and it is a sensitive and powerful analytical tool for insulating materials and semiconductors. Most studies so far have focused on visible and UV emission spectra as the spectra reveal information on the formation and types of defect sites. The modifications are dependent on ionisation density, and synergistic effects with nuclear collision damage. There is thus the ability to track defect production and amorphisation of crystalline hosts. Further, ion beam excited luminescence is equally a useful probe for studying nanoparticle growth. Such data can be obtained at different implantation temperatures or combined with other thermal treatments. Pulsed ion beams have the potential to reveal variations in defect formation by lifetime resolution of the signals. However, there is far greater analytical potential which has not been widely developed. The current article will describe how to extend the effects of lifetime resolution; to detect phase transitions, both stable and transient; and the opportunities which arise from combining the ion beam induced luminescence signals with simultaneous excitation of the materials with photons, electrons or X-rays. The combination of two methods can differ from the sum of separate excitation irradiations and so offer details on metastable structures related to ion implantation. Site specific probes using rare earth doped materials during implantation to form laser waveguide structures can track relaxations of both the guide and boundary regions. The measurement of ion beam luminescence spectra and lifetime data over a wide temperature range have historically been under exploited. Parallel data from optical absorption taken during implantation can be similarly informative. Benefits from all such measurements will be discussed.
29 citations
15 May 2014-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a detailed analysis of the radioluminescence emissions and their response to irradiation and thermal treatments of quartz has been carried out and the role of Al-related centres in the luminescence properties of quartz was confirmed.
Abstract: Quartz is an extremely diffused natural luminescence dosimeter. Thanks to the presence of traps and luminescence centres, its TSL and OSL (Thermally and Optically Stimulated Luminescence) properties have been extensively exploited. Quartz is then used for archaeological and geological dating and is one of the most useful materials for accident dosimetry. Many luminescence emissions are known to be present in the OSL and TSL of quartz. Three main emission bands are always reported, as the red, blue and UV bands, centred at around 650, 470, and 360–380 nm, respectively. Although the assignment of the luminescence emissions to specific defect centres in quartz is still undefined, a thorough analysis of the radioluminescence emissions and their response to irradiation and thermal treatments turned out to be very useful in understanding many features. Specifically, the presence of the same emission bands in natural and synthetic quartz and their dependence on the presence of extrinsic impurities is a common characteristic. The main impurities involve Al ions substituting Si ones and charge compensated by nearby either alkali ions, H + , or a hole. The emission spectra dynamics evidenced in our experiment confirm the role of Al-related centres in the luminescence properties of quartz. From the measurements presented in this paper the composite nature of the “blue” emission is confirmed. Two bands labelled as A at 2.5 eV and B at 2.8 eV contribute to the emission in this region, their behaviour being different as a function of irradiation. More complex is the picture in the UV region, where, besides the already detected C and D bands at 3.4 eV and 3.9 eV, respectively, two further emissions have been detected at 3.1 eV and 3.7 eV. Despite both the 3.4 eV and the 3.7 eV bands are shown to be affected by thermal treatments, the annealing temperature dependence of their intensity is markedly different. In fact, whereas the C band intensity, at 3.4 eV, increases after annealing at 500 °C followed by a decrease at higher temperatures, the 3.7 eV intensity is strongly enhanced by annealing at temperature above 700 °C and reaches its highest value after annealing at around 1000 °C. In the light of these results a number of already known features of quartz emissions should be reconsidered.
23 citations
TL;DR: A general and automated graph-based approach to extract all chemically distinct structures sampled in QMD simulations and applies this approach to predict primary radiation damage of polydimethylsiloxane (PDMS), the main constituent of silicones.
Abstract: Initial atomistic-level radiation damage in chemically reactive materials is thought to induce reaction cascades that can result in undesirable degradation of macroscale properties. Ensembles of quantum-based molecular dynamics (QMD) simulations can accurately predict these cascades, but extracting chemical insights from the many underlying trajectories is a labor-intensive process that can require substantial a priori intuition. We develop here a general and automated graph-based approach to extract all chemically distinct structures sampled in QMD simulations and apply our approach to predict primary radiation damage of polydimethylsiloxane (PDMS), the main constituent of silicones. A postprocessing protocol is developed to identify underlying polymer backbone structures as connected components in QMD trajectories. These backbones form a repository of radiation-damaged structures. A scheme for extracting and updating a library of isomorphically distinct structures is proposed to identify the spanning set and aid chemical interpretation of the repository. The analyses are applied to ensembles of cascade QMD simulations in which the four element types in PDMS are selectively excited in primary knock-on atom events. Our approach reveals a much higher degree of combinatorial complexity in this system than was inferred through radiolysis experiments. Probabilities are extracted for radiation-induced network changes including formation of branch points, carbon linkages, cycles, bond scissions, and carbon uptake into the Si-O siloxane backbone network. The general analysis framework presented here is readily extendable to modeling chemical degradation of other polymers and molecular materials and provides a basis for future quantum-informed multiscale modeling of radiation damage.
11 citations
References
More filters
Book•
IBM1
TL;DR: A review of existing widely-cited tables of ion stopping and ranges can be found in this paper, where a brief exposition of what can be determined by modern calculations is given.
Abstract: The stopping and range of ions in matter is physically very complex, and there are few simple approximations which are accurate. However, if modern calculations are performed, the ion distributions can be calculated with good accuracy, typically better than 10%. This review will be in several sections:
a)
A brief exposition of what can be determined by modern calculations.
b)
A review of existing widely-cited tables of ion stopping and ranges.
c)
A review of the calculation of accurate ion stopping powers.
10,060 citations
TL;DR: In this paper, the theory of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment.
Abstract: The theory of the kinetics of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment. The density of germ nuclei diminishes through activation of some of them to become growth nuclei for grains of the new phase, and ingestion of others by these growing grains. The quantitative relations between the density of germ nuclei, growth nuclei, and transformed volume are derived and expressed in terms of a characteristic time scale for any given substance and process. The geometry and kinetics of a crystal aggregate are studied from this point of view, and it is shown that there is strong evidence of the existence, for any given substance, of an isokinetic range of temperatures and concentrations in which the characteristic kinetics of phase change remains the same. The determination of phase reaction kinetics is shown to depend upon the solution of a functional equation of a certain type. Some of the general properties of temperature‐time and transformation‐time curves, respectively, are described and explained.
9,458 citations
TL;DR: In this paper, free standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography using electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers.
Abstract: Indirect evidence is presented that free‐standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography. The novel approach uses electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers. Mesoporous Si layers of high porosity exhibit visible (red) photoluminescence at room temperature, observable with the naked eye under <1 mW unfocused (<0.1 W cm−2) green or blue laser line excitation. This is attributed to dramatic two‐dimensional quantum size effects which can produce emission far above the band gap of bulk crystalline Si.
7,393 citations
TL;DR: A large amount of work world wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si as mentioned in this paper, and the key importance of crystalline Si nanostructures in determining the behaviour of porous si is highlighted.
Abstract: A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.
2,371 citations
2,353 citations