[en] We report the use of ion beam induced charge imaging to characterise the charge signal uniformity of epitaxial gallium nitride radiation detectors. The detectors were fabricated from 2 μm thick semi-insulating gallium nitride, grown by MOCVD on a sapphire substrate. A carrier concentration of 1.4x10¹⁵ cm^-3 was measured using capacitance-voltage measurements. Ion beam induced charge imaging was carried out with a 2 MeV alpha particle beam focussed to a 3 μm diameter and raster scanned across the device. The resulting ion beam images show excellent charge signal uniformity in this material with no evidence of material defects or polycrystalline structure on the micrometer length scale. No evidence of charge signal trapping was observed in these devices

No abstract available

[en] Atomic-force and Kelvin-probe microscopies were employed in ultrahigh vacuum to image the surface topography and contact potential of the hydrogen-terminated and unterminated surfaces of diamond. A variation of about 25 meV in the contact potential was measured on a length scale of 20 nm and ascribed to differently orientated surface domains resulting from hydrogen-plasma processing of the sample. Shifts in the work function arising from sample heating in vacuum and the adsorption of C₆₀ were measured. The Fermi level was found to be 0.7 and 1.1 eV below the valence band maximum for C₆₀ coverages of 1 and 4 monolayer, respectively.

[en] Full text: Nanodiamonds (NDs) with nitrogen vacancy (NV) centres have been shown to be useful for applications involving cellular tracking in vivo at the molecular level. The sustained fluorescence of these nanodiamonds is related to their structure, and is supposed to be influenced by the strain distribution inside the crystals. In nanocrystals even relatively small amounts of strain can induce large changes in the mechanical, optical and electronic properties of nanocrystals. The current work elaborates first application of Bragg coherent diffractive imaging (BCDI) for mapping the three-dimensional (3D) strain fields within the crystalline nanodiamonds. For reference, a control sample (as-grown crystals) has been compared with a strain-induced (implanted with 1012 ions per cm²) sample. The comparison of control and strain-induced samples will help to optimise their application for tracking the processes at molecular level. (author)

[en] Three-dimensional imaging of protein crystals during x-ray diffraction experiments opens up a range of possibilities for optimizing crystal quality and gaining new insights into the fundamental processes that drive radiation damage. Obtaining this information at the appropriate length-scales however is extremely challenging. One approach that has been recently demonstrated as a promising avenue for characterizing the size and shape of protein crystals at nanometre length-scales is Bragg coherent diffractive imaging (BCDI). BCDI is a recently developed technique that is able to recover the phase of the continuous diffraction intensity signal around individual Bragg peaks. When data is collected at multiple points on a rocking curve, a reciprocal space map (RSM) can be assembled and then inverted using BCDI to obtain a three-dimensional image of the crystal. The first demonstration of two-dimensional biological BCDI was reported by Boutet et al on holoferritin, recently this work was extended to the study of radiation damage in micron-sized protein crystals. Here we present the first three-dimensional reconstructions of a Lysozyme protein crystal using BDI. The results are validated against RSM and transmission electron microscopy data and have implications for both radiation damage studies and for developing new approaches for structure retrieval from micron-sized protein crystals. (paper)