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Global quantum networks will benefit from the reliable creation and control of high-performance solid-state telecom photon-spin interfaces. T radiation damage centres in silicon provide a promising photon-spin interface due to their narrow O-band optical transition near 1326 nm and long-lived electron and nuclear spin lifetimes. To date, these defect centres have only been studied as ensembles in bulk silicon. Here, we demonstrate the reliable creation of high concentration T centre ensembles in the 220 nm device layer of silicon-on-insulator (SOI) wafers by ion implantation and subsequent annealing. We then develop a method that uses spin-dependent optical transitions to benchmark the characteristic optical spectral diffusion within these T centre ensembles. Using this new technique, we show that with minimal optimization to the fabrication process high densities of implanted T centres localized $\lesssim$100 nm from an interface display ~1 GHz characteristic levels of total spectral diffusion., 10 pages, 9 figures

The global quantum internet will require long-lived, telecommunications band photon-matter interfaces manufactured at scale. Preliminary quantum networks based upon photon-matter interfaces which meet a subset of these demands are encouraging efforts to identify new high-performance alternatives. Silicon is an ideal host for commercial-scale solid-state quantum technologies. It is already an advanced platform within the global integrated photonics and microelectronics industries, as well as host to record-setting long-lived spin qubits. Despite the overwhelming potential of the silicon quantum platform, the optical detection of individually addressable photon-spin interfaces in silicon has remained elusive. In this work we produce tens of thousands of individually addressable `$T$ centre' photon-spin qubits in integrated silicon photonic structures, and characterize their spin-dependent telecommunications-band optical transitions. These results unlock immediate opportunities to construct silicon-integrated, telecommunications-band quantum information networks., Comment: 25 pages, 10 figures

Brownian thermal noise in dielectric multilayer coatings limits the sensitivity of current and future interferometric gravitational wave detectors. In this work we explore the possibility of improving the mechanical losses of tantala, often used as the high refractive index material, by depositing it on a substrate held at elevated temperature. Promising results have been previously obtained with this technique when applied to amorphous silicon. We show that depositing tantala on a hot substrate reduced the mechanical losses of the as-deposited coating, but subsequent thermal treatments had a larger impact, as they reduced the losses to levels previously reported in the literature. We also show that the reduction in mechanical loss correlates with increased medium range order in the atomic structure of the coatings using x-ray diffraction and Raman spectroscopy. Finally, a discussion is included on our results, which shows that the elevated temperature deposition of pure tantala coatings does not appear to reduce mechanical loss in a similar way to that reported in the literature for amorphous silicon; and we suggest possible future research directions.

We present an investigation of Mn ��-doped layers in Si(001) grown by molecular beam epitaxy. We discovered that a Pb surfactant has significant effect on the structural and magnetic properties of the submonolayer of Mn, which depends on the Si capping layer growth temperature, T_Si, and the Mn coverage, ��_Mn. The results presented in this paper identify three regions in the growth-phase-diagram characterized by distinct magnetic behaviors and crystal structures. In one region, X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM) experiments indicate that MnSi nanocrystallites form with B2-like crystal type structures. At the optimal growth conditions, T_Si = 200 C and ��_Mn = 0.26 monolayer, a ferromagnetic phase develops with a Curie temperature T_C > 400 K and a saturation moment m_sat = 1.56 ��_B/Mn, whereas T_C drops to zero for a control sample prepared without Pb. For T_Si > 200 C, MnSi-B20 type precipitates form with a T_C ~ 170 K. Rutherford backscattering spectroscopy shows that the increase in the remanent magnetization in these two phases is possibly correlated with an increase in the Mn substitutional fraction, which suggests that a Si_{1-x}Mn_x dilute magnetic semiconductor may be forming in the matrix between the precipitates. Density functional calculations show that Pb changes the pathway by which the Mn atoms access the Si substitutional sites, Mn_Si. While the Pb increases the formation energy of Mn_Si at the Si surface, it enables substitutional incorporation by lowering the formation energy of Si vacancies by 0.92 eV., 10 pages, 8 figures

We have investigated the effect of Yb substitution on the Pauli-limited, heavy-fermion superconductor, CeCoIn5. Yb acts as a non-magnetic divalent substituent for Ce throughout the entire doping range, equivalent to hole doping on the rare-earth site. We found that the upper critical field in (Ce,Yb)CoIn5 is Pauli limited, yet the reduced (H,T) phase diagram is insensitive to disorder, as expected in the purely orbitally limited case. We use the Pauli-limiting field, the superconducting condensation energy and the electronic specific-heat coefficient to determine the Wilson ratio (RW), the ratio of the specific-heat coefficient to the Pauli susceptibility in CeCoIn5. The method is applicable to any Pauli-limited superconductor in the clean limit. © EPLA, 2010.

We have used tight-binding molecular-dynamics simulations to investigate the role of point defects (vacancies and interstitials) on structural relaxation in amorphous silicon. Our calculations give unambiguous evidence that point defects can be defined in the amorphous solid, showing up as anomalies in the valence-charge/Voronoi-volume relation. The changes in the radial distribution functions that take place during annealing are shown to be in close agreement with recent, highly-accurate x-ray diffraction measurements. Our calculations provide strong evidence that structural relaxation in a-Si proceeds by the mutual annihilation of vacancies and interstitials, i.e., local structural changes rather than an overall relaxation of the network., Comment: 6 pages including 2 .eps figures; submitted to Physical Review Letters; additional publications on this and related topics can be found on web site http://www.esi.umontreal.ca/~grofnum

In order to investigate the role of hydrogen in amorphous silicon (a-Si), hydrogenated amorphous silicon layers have been prepared by ion implantation at different H concentrations. Implanted samples have been characterized before and after annealing up to 550 °C by small-angle x-ray scattering, secondary-ion-mass spectrometry, and infrared spectroscopy. The study of the evolution of hydrogen concentration profiles and bonding configurations combined with the investigation of the atomic and nanoscale structures of the films indicate the solubility limit of hydrogen in a-Si to lie at 3–4 at. %. This limit is associated with the defect-related trap concentration in a-Si. If hydrogen is introduced in the matrix at a concentration well above its solubility, the alloy is intrinsically unstable to the formation of hydrogen complexes. Upon annealing at temperatures higher than 300 °C, the excess H (i.e., above the solubility) leaves the matrix, presumably forming H2 molecules, which accumulate in nanoscale hydrogen complexes. Observations on nucleation and growth of these hydrogen complexes are discussed in light of H diffusion and solubility.

International audience; We report on the cross-calibration of Thomson Parabola (TP) and Time-of-Flight (TOF) detectors as particle diagnostics, implemented on the most recent setup of the ALLS 100 TW laser-driven ion acceleration beamline. The Microchannel Plate (MCP) used for particle detection in the TP spectrometer has been calibrated in intensity on the tandem linear accelerator at the Université de Montréal. The experimental data points of the scaling factor were obtained by performing a pixel cluster analysis of single proton impacts on the MCP. A semi-empirical model was extrapolated and fitted to the data to apply the calibration also to higher kinetic energies and to extend it to other ion species. Two TOF lines using diamond detectors, placed at +6° and −9° with respect to the target-normal axis, were benchmarked against the TP spectrometer measurements to determine the field integrals related to its electric and magnetic dispersions. The mean integral proton numbers obtained on the beamline were about 4.1 × 1011 protons/sr with a standard deviation of 15% in the central section of the spectrum around 3 MeV, hence witnessing the high repeatability of the proton bunch generation. The mean maximum energy was of 7.3 ± 0.5 MeV, well in agreement with similar other 100 TW-scale laser facilities, with the best shots reaching 9 MeV and nearly 1012 protons/sr. The used particle diagnostics are compatible with the development of a high-repetition rate targetry due to their fast online readout and are therefore a crucial step in the automation of any beamline

This study compares oxide and nitride formation during oxygen and nitrogen bombardment of Si. Ion bombardment is carried out both in a SIMS machine and in a conventional implanter at various temperatures. Stoichiometric SiO2 and slightly N-rich Si3N4 are formed during bombardment even at cryogenic temperatures. Implanted metals were found to have a strong tendency to be segregated at a moving Si-SiO2 interface during oxygen bombardment but little segregation is observed at a Si-Si3N4 interface.