Publications (2)1.88 Total impact
Article: Low-loss EELS of 2D boron nitride[show abstract] [hide abstract]
ABSTRACT: Electron energy loss spectroscopy provides a probe of the dielectric function of a material which can be affected by the size and morphology of a sample. In this paper, the effect on the loss function when hexagonal boron nitride is reduced to a single layer is investigated. The previously predicted red-shift of the spectrum is seen in experiment and reproduced by modelling using density functional theory. The dielectric function shows that, for a single layer, the lack of screening causes the real part of the dielectric function to tend to 1 so that the loss function resembles the imaginary part of the dielectric function.Journal of Physics Conference Series 01/2012; 371(1).
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ABSTRACT: We compare the near edge structure (NES) of cubic boron nitride (cBN) measured using both electron energy loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS) with that calculated using three commonly used theoretical approaches. The boron and nitrogen K-edges collected using EELS and XAS from cBN powder were found to be nearly identical. These experimental edges were compared to calculations obtained using an all-electron density functional theory code (WIEN2k), a pseudopotential density functional theory code (CASTEP) and a multiple scattering code (FEFF). All three codes were found to reproduce the major features in the NES for both ionisation edges when a core-hole was included in the calculations. A partial core hole (1/2 of a 1s electron) was found to be essential for correctly reproducing features near the edge threshold in the nitrogen K-edge and to correctly obtain the positions of all main peaks. CASTEP and WIEN2k were found to give almost identical results. These codes were also found to produce NES which most closely matched experiment based on χ² calculations used to qualitatively compare theory and experiment. This work demonstrated that a combined experimental and theoretical approach to the study of NES is a powerful way of investigating bonding and electronic structure in boron nitride and related materials.Micron 07/2011; 43(1):43-8. · 1.88 Impact Factor