We present a high throughput and systematic method for screening of colour centres in diamond. We aim at the search and reproducible creation of new optical centres, down to the single level, potentially of interest for the wide range of diamond-based quantum applications. The screening method presented here should moreover help identifying some already indexed defects among hundreds in diamond [1] but also some promising defects of still unknown nature, such as the recently discovered ST1 centre [2,3]. We use ion implantation in a systematic manner to implant several chemical elements. Ion implantation has the advantage to address single atoms inside the bulk with defined depth and high lateral resolution, but the disadvantage of defect production such as vacancies. The sample is annealed in vacuum at different temperatures (between 600°C and 1600°C with 200°C steps) and fully characterised at each step in order to follow the evolution of the defects: formation, dissociation, diffusion, reformation and charge state, at the ensemble level and, if possible, at the single centre level. We review the unavoidable ion implantation defects (with the example of the GR1 and 3H centres), discuss ion channeling and thermal annealing and estimate the diffusion of vacancies, nitrogen and hydrogen. We use different characterisation methods best suited for our study (from widefield fluorescence down to sub-diffraction optical imaging of single centres) and discuss reproducibility issues due to diamond and defect inhomogeneities. Nitrogen is also implanted as a reference, taking advantage of the large knowledge on NV centres as a versatile sensor in order to retrieve or deduce the conditions and local environment in which the different implanted chemical elements are embedded. We show here the preliminary promising results of a long-term study and focus on the elements O, Mg, Ca, F and P, from which fluorescent centres were found.

Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10−9 in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by Si sublimation, under higher magnetic fields. Here, we report on a graphene device grown by chemical vapour deposition on SiC, which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron-density devices.

Epitaxial graphene films grown on silicon carbide ͑SiC͒ substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of epitaxial graphene films on 3C-SiC͑111͒/Si͑111͒ substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene ͑FLG͒ surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.

We propose to grow graphene on SiC by a direct carbon feeding through propane flow in a chemical vapor deposition reactor. X-ray photoemission and low energy electron diffraction show that propane allows to grow few-layer graphene (FLG) on 6H-SiC(0001). Surprisingly, FLG grown on (0001) face presents a rotational disorder similar to that observed for FLG obtained by annealing on (000–1) face. Thanks to a reduced growth temperature with respect to the classical SiC annealing method, we have also grown FLG/3C-SiC/Si(111) in a single growth sequence. This opens the way for large-scale production of graphene-based devices on silicon substrate.

Cathodoluminescence reveals structures indicative of gas-assisted epitaxial growth during chondrule melt crystallization.

International audienceStructural and electronic properties of epitaxial graphene on 3C-SiC(111) pseudosubstrate epilayers on silicon was investigated in detail by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), scanning transmission electron microscopy (STEM), and synchrotron angle-resolved photoemission spectroscopy (ARPES). The graphitization process has been observed by distinct features in the atomically resolved STM images and abrupt interface with the number of stacked-graphene layer has been revealed in STEM image. Two different types of carbon atom networks, honeycomb and one sublattice, were atomically resolved by STM. Electronic properties and band structures of the epitaxial graphene are examined with angle-resolved photoemission spectroscopy, showing linear band dispersion K point of the Brillouin zone, with Dirac point about 500 meV below the Fermi level (E-F). These findings are of relevance for various potential applications based on graphene-SiC/Si(111) structures

Graphene has emerged as a promising nanoelectronic material in electronic devices applications and studying two-dimensional electron gases with relativistic dispersion near Dirac point. Nonetheless, the control of the preparation conditions for homogeneous large-area graphene layers is difficult. Here, we illustrate evidence for high structural and electronic quality epitaxial graphene on 3C–SiC(111). Morphology and electronic structure of the graphene layers have been analyzed with low energy electron microscopy and angle resolved photoemission spectroscopy. Using scanning tunneling microscopy and scanning transmission electron microscopy, we show that graphene exhibits remarkably continuity of step edges suggesting the possibility of growing large scale graphene layer.

Graphene growth from a propane flow in a hydrogen environment (propane-hydrogen chemical vapor deposition (CVD)) on SiC differentiates from other growth methods in that it offers the possibility to obtain various graphene structures on the Si-face depending on growth conditions. The different structures include the (6√3 × 6√3)-R30° reconstruction of the graphene/SiC interface, which is commonly observed on the Si-face, but also the rotational disorder which is generally observed on the C-face. In this work, growth mechanisms leading to the formation of the different structures are studied and discussed. For that purpose, we have grown graphene on SiC(0001) (Si-face) using propane-hydrogen CVD at various pressure and temperature and studied these samples extensively by means of low energy electron diffraction and atomic force microscopy. Pressure and temperature conditions leading to the formation of the different structures are identified and plotted in a pressure-temperature diagram. This diagram, together with other characterizations (X-ray photoemission and scanning tunneling microscopy), is the basis of further discussions on the carbon supply mechanisms and on the kinetics effects. The entire work underlines the important role of hydrogen during growth and its effects on the final graphene structure.