Creating diamond color centers for quantum optical applications

Nitrogen vacancy (NV) centers in diamond have distinct promise as solid-state qubits. This is because of their large dipole moment, convenient level structure and very long room-temperature coherence times. In general, a combination of ion irradiation and subsequent annealing is used to create the centers, however for the rigorous demands of quantum computing all processes need to be optimized, and decoherence due to the residual damage caused by the implantation process itself must be mitigated. To that end we have studied photoluminescence (PL) from NV$^-$, NV$^0$ and GR1 centers formed by ion implantation of 2MeV He ions over a wide range of fluences. The sample was annealed at $600^{\circ}$C to minimize residual vacancy diffusion, allowing for the concurrent analysis of PL from NV centers and irradiation induced vacancies (GR1). We find non-monotic PL intensities with increasing ion fluence, monotonic increasing PL in NV$^0$/NV$^-$ and GR1/(NV$^0$ + NV$^1$) ratios, and increasing inhomogeneous broadening of the zero-phonon lines with increasing ion fluence. All these results shed important light on the optimal formation conditions for NV qubits. We apply our findings to an off-resonant photonic quantum memory scheme using vibronic sidebands

3D-Hydrogen Analysis of Ferromagnetic Microstructures in Proton Irradiated Graphite

Recently, magnetic order in highly oriented pyrolytic graphite (HOPG) induced by proton broad- and microbeam irradiation was discovered. Theoretical models propose that hydrogen could play a major role in the magnetism mechanism. We analysed the hydrogen distribution of pristine as well as irradiated HOPG samples, which were implanted to micrometer-sized spots as well as extended areas with various doses of 2.25 MeV protons at the Leipzig microprobe LIPSION. For this we used the sensitive 3D hydrogen microscopy system at the Munich microprobe SNAKE. The background hydrogen level in pristine HOPG is determined to be less than 0.3 at-ppm. About 4.8e15 H-atoms/cm^2 are observed in the near-surface region (4 um depth resolution). The depth profiles of the implants show hydrogen located within a confined peak at the end of range, in agreement with SRIM Monte Carlo simulations, and no evidence of diffusion broadening along the c-axis. At sample with microspots, up to 40 at-% of the implanted hydrogen is not detected, providing support for lateral hydrogen diffusion.Comment: accepted for publication in Nucl. Instr. and Met

Production of Υ(nS) mesons in Pb+Pb and pp collisions at 5.02 TeV

A measurement of the production of vector bottomonium states, Υ ( 1S ) , Υ ( 2S ) , and Υ ( 3S ) , in Pb + Pb and p p collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb − 1 of Pb + Pb data collected in 2018, 0.44 nb − 1 of Pb + Pb data collected in 2015, and 0.26 fb − 1 of p p data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum p μ μ T < 30 GeV , absolute rapidity | y μ μ | < 1.5 , and Pb + Pb event centrality 0–80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in p p collisions to extract the nuclear modification factors as functions of event centrality, p μ μ T , and | y μ μ | . In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations

Nuclear microscopy of Fe substituted 2212 BiSrCaCuO superconducting crystals

Nuclear Inst. and Methods in Physics Research, B1041-4561-565NIMB

Focused microprobes of high energy ions - versatile analytical probes for surfaces, interfaces and devices

10.1016/S0169-4332(00)00737-6Applied Surface Science169-170134-141ASUS

Raman investigation of damage caused by deep ion implantation in diamond

Raman microscopy has been employed to investigate the nature of damage created when natural type-IIa diamond is irradiated with MeV alpha particles. Three features appear in the Raman spectrum due to damage, viz., (i) the first-order diamond Raman line is broadened and downshifted, (ii) broad features appear which are a measure of the vibrational density of states of ion-beam-amorphized diamond, and (iii) the damage causes the appearance of sharp defect-induced Raman peaks at 1490 and 1630 cm-1. For damage below an amorphization threshold, a linear relationship exists between the full width at half maximum and frequency shift, which shows that these are Kramers-Kronig related. The annealing behavior of the sharp Raman feature at 1490 cm-1 suggests that this peak is associated with vacancies with an activation energy for annealing of 4.06 eV, while the 1630-cm-1 peak is due to an interstitial related defect with an activation energy of 1.2 eV. For sub-MeV ion irradiation, damage beyond the critical amorphization level usually leads to relaxation of the diamond structure to graphite upon thermal annealing. However, for MeV ion irradiation, it was found that annealing, even when the ion induced damage level is well above the amorphization threshold, could restore the original diamond structure. We attribute this result to the high internal pressure the damaged layer is subjected to which does not allow relaxation to graphitically bonded structures

Carbon diffusion and nanocrystalline diamond formation in carbon ion-implanted oxides studied by nuclear elastic scattering

We have shown that MeV implantation of carbon into fused quartz and sapphire followed by thermal annealing in a suitable environment can result in the formation of diamond. Using cross-sectional transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS), we determined (in a previous paper) that, following annealing, there was a redistribution of carbon from the original implantation depth, depending on the annealing environment, annealing time and annealing temperature. In our search, for the optimum implantation and annealing parameters to maximize the yield of diamond, we have used backscattering spectrometry (BS), with MeV hydrogen, to profile the implanted carbon, taking advantage of the large C(p,p)C scattering cross-section at around 1.73 MeV. We studied samples of fused quartz and sapphire implanted with carbon to a range of doses and annealed in forming gas, oxygen and argon. We show that in an oxygen environment, there is significant carbon loss in fused quartz but not in sapphire while in the other environments no significant loss is reported. We conclude that redistribution of carbon, the formation of nanocrystalline diamond (as seen in cross-sectional TEM) and possible carbon loss is determined both by the mobility of carbon in the host matrix at the prevailing annealing temperatures and, most importantly, the annealing ambient

Imaging Ni segregation in synthetic diamond using ionoluminescence (IL) and particle induced X-ray emission (PIXE)

10.1016/S0168-583X(01)00459-1Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms1811-4225-230NIMB