s should clearly state the purpose, brief statement of procedure, results and conclusions. Please include your name, full address and topic on all submissions. At least one author of each abstract should register for the conference. All accepted abstracts will be published as symposium proceedings. Additionally, commended abstracts may be published in a journal after they are expanded to a manuscript followed by extensive reviewing. The language of the conference will be English.

An international symposium

The exploitation of emerging quantum technologies requires efficient fabrication of key building blocks. Sources of single photons are extremely important across many applications as they can serve as vectors for quantum information—thereby allowing long-range (perhaps even global-scale) quantum states to be made and manipulated for tasks such as quantum communication or distributed quantum computation. At the single-emitter level, quantum sources also afford new possibilities in terms of nanoscopy and bio-marking. Color centers in diamond are prominent candidates to generate and manipulate quantum states of light, as they are a photostable solid-state source of single photons at room temperature. In this review, we discuss the state of the art of diamond-based single-photon emitters and highlight their fabrication methodologies. We present the experimental techniques used to characterize the quantum emitters and discuss their photophysical properties. We outline a number of applications including quantum key distribution, bio-marking and sub-diffraction imaging, where diamond-based single emitters are playing a crucial role. We conclude with a discussion of the main challenges and perspectives for employing diamond emitters in quantum information processing.

https://iopscience.iop.org/article/10.1088/0034-4885/74/7/076501/pdf

Diamond-based single-photon emitters

We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.

Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium

When collimated beams of low energy ions are used to bombard materials, the surface often develops a periodic pattern or “ripple” structure. Different types of patterns are observed to develop under different conditions, with characteristic features that depend on the substrate material, the ion beam parameters, and the processing conditions. Because the patterns develop spontaneously, without applying any external mask or template, their formation is the expression of a dynamic balance among fundamental surface kinetic processes, e.g., erosion of material from the surface, ion-induced defect creation, and defect-mediated evolution of the surface morphology. In recent years, a comprehensive picture of the different kinetic mechanisms that control the different types of patterns that form has begun to emerge. In this article, we provide a review of different mechanisms that have been proposed and how they fit together in terms of the kinetic regimes in which they dominate. These are grouped into regions of behavior dominated by the directionality of the ion beam, the crystallinity of the surface, the barriers to surface roughening, and nonlinear effects. In sections devoted to each type of behavior, we relate experimental observations of patterning in these regimes to predictions of continuum models and to computer simulations. A comparison between theory and experiment is used to highlight strengths and weaknesses in our understanding. We also discuss the patterning behavior that falls outside the scope of the current understanding and opportunities for advancement.

Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering

A number of models have been developed to describe the various amorphization processes and the effects of temperature on the kinetics of amorphization. These models are reviewed and in some cases further developed. In general, these models contain a number of parameters relating to irradiation-assisted and thermal recovery processes, which make their application to existing data sets challenging. Nonetheless, general aspects of the models yield insights into the rate-limiting processes controlling the kinetics of amorphization within a given temperature regime. Several examples are used to illustrate features of the models and to highlight differences in behavior.

Models and mechanisms of irradiation-induced amorphization in ceramics

A detailed investigation of ion-beam induced atomic transport through bi-layer interfaces of low- and medium-Z metals and their nitrides as a function of the irradiation conditions and the materials combinations allowed us to distinguish between five different mixing mechanisms. In the strongly bound nitrides ballistic transport dominates the atomic intermixing, while for the metallic bi-layers diffusion in local (light- and medium-mass ions) and global thermal spikes (very heavy ions) seems to be the major mixing mechanism. Heavy ions were also found to initiate end-of-range spikes even in systems where mixing in the recoil cascade is of purely ballistic character. Besides these athermal processes, irradiaion at higher temperatures may result in thermally activated radiation-enhanced diffusion .

Ion-beam induced atomic transport through bi-layer interfaces of low- and medium-Z metals and their nitrides

The topography of (0001)-graphite (highly oriented pyrolytic graphite) surfaces eroded by a 5 keV ${\mathrm{Xe}}^{+}$ ion beam has been investigated using scanning tunneling microscopy. For tilted incidence of the ion beam and ion fluences of about ${10}^{17} {\mathrm{cm}}^{\ensuremath{-}2},$ a quasiperiodic ripple topography with characteristic wavelengths between 40 and 70 nm has been found. As predicted by continuum theory and Monte Carlo simulations, below a critical angle ${\ensuremath{\theta}}_{C}$ the ripples are oriented perpendicular to the ion beam projection onto the surface, while for angles above ${\ensuremath{\theta}}_{C}$ the ripple orientation is parallel to the ion beam projection. The critical angle ${\ensuremath{\theta}}_{C}$ lies between $60\ifmmode^\circ\else\textdegree\fi{}$ and $70\ifmmode^\circ\else\textdegree\fi{},$ in agreement with the predictions of the continuum theory. For rising ion fluences, large scale perturbations of the surface topography occur indicating a nonlinear behavior governed by the Kardar-Parisi-Zhang universality class.

Nanometer ripple formation and self-affine roughening of ion-beam-eroded graphite surfaces

We have investigated the irradiation induced interface mixing in ZnO/SiO2 (α-quartz) and Sb/Ni/Si thin layer systems under swift heavy ion irradiation in the electronic stopping power regime. The irradiations were carried out at 77 K using 100 MeV Ar, 260 MeV Kr, and 200 MeV Xe ions. For the ZnO/SiO2 system experiments were also carried out at lower ion energies (300, 600, and 900 keV, respectively) where nuclear stopping dominates. The alterations of the interface concentration profiles were determined by means of Rutherford backscattering spectrometry performed subsequently at the irradiated and the nonirradiated parts of the samples. While for the semimetal/metal Sb/Ni interface almost no mixing could be found after high-energy irradiation (mixing efficiency for Xe ions: k/Se<0.02 nm5/keV) the ceramic system ZnO/SiO2 strongly reacts upon high energy ion irradiation (Xe: k/Se=2.1 nm5/keV). The Ni/Si interface shows an intermediate effect (Xe: k/Se=0.2 nm5/keV). The mixing behavior found at high ion ener...

Ion beam mixing of ZnO/SiO2 and Sb/Ni/Si interfaces under swift heavy ion irradiation

In the present paper recent studies on the amorphization and recrystallization of the light covalent ceramics SiC, Si3N4 and SiO2 (and in comparison Si) shall be reviewed. By combining long and short range order sensitive analysis techniques new insights into the disordering/reordering mechanisms and the structure of the disordered materials were gained. The results will be discussed in the light of a topological approach of the transition between periodic and aperiodic networks.

Amorphization and recrystallization of covalent tetrahedral networks

In the present paper the results of an extended study on the disordering of Si, SiC, Si 3 N 4 and SiO 2 by ion bombardment will be reviewed, with respect to both long and short range order. It was found that amorphization occurs by nucleation and growth of defect agglomerates in the still crystalline matrix, until a critical damage density is achieved and a transition between the ordered and the disordered networks occurs. In SiO 2 , Si 3 N 4 and Si the disordered phase consists of a random network of [SiX 4 ]-tetrahedrons (X = O, N, Si), which conserved the chemical short range order of the crystalline materials. In SiC first a highly disordered network of [SiC 4 ]-tetrahedra forms, which is however not as random as in the other materials, since a correlation between the orientation of neighboring tetrahedra exists. Further bombardment of this network then results in complete destruction of the initial chemical short range order and the formation of Si–Si and C–C bonds. The results are compared with theoretical predictions of the amorphizability of the different compounds and the microstructure of the disordered phases.

Wolfgang Bolse

Papers

Ion-beam induced atomic transport through bi-layer interfaces of low- and medium-Z metals and their nitrides

Nanometer ripple formation and self-affine roughening of ion-beam-eroded graphite surfaces

Ion beam mixing of ZnO/SiO2 and Sb/Ni/Si interfaces under swift heavy ion irradiation

Amorphization and recrystallization of covalent tetrahedral networks

Formation and development of disordered networks in Si-based ceramics under ion bombardment