An EELS and XAS Study of Cubic Boron Nitride Synthesized under High Pressure - High Temperature Conditions

Abstract

Abstract. 2014 Cubic Boron Nitride (c-BN) single-crystals have been synthesized under high pressure and high temperature conditions (HP -HT) using hexagonal Boron Nitride (h-BN) precursors. We have performed a study of both phases with electron (EELS) and X-ray (XAS) spectroscopy that are compared. The c-BN ELNES spectra at B-K and N-K edges are found to be consistent with the XANES (XAS) data, although the energy resolution achieved with X-rays is better than that obtained by EELS with a LaB6 filament. However, XAS is at a disadvantage by comparison with EELS owing to the presence of the N-K edge second order. Attempts were made to dope c-BN with carbon atoms. The examination of the EELS spectra reveals that the incorporation of carbon species in the BN material is always accompanied by the addition of oxygen. Several samples were analyzed both with selected area electron diffraction and energy loss spectroscopy. Most probed crystals containing C (and therefore O) were found to be hexagonal. These results emphasized that the range of existence of the cubic phase is very narrow around the binary composition.

Extending the analysis of EELS spectrum-imaging data, from elemental to bond mapping in complex nanostructures

“…The reference spectra of Fig. 4(c) match well with those from the literature for: boron [39], boron oxide [40] and h-BN [41][42][43]. Comparing the first four original source data, from the bottom (Fig.…”

“…The effect is observable in the magnitude of the p à peak at 191.8 eV (characteristic of the sp 2 hybridization) relative to the s à peak. This phenomenon has been studied experimentally and theoretically by different authors [41][42][43][44][45][46]. In this work, two references were chosen associated with the two extreme (lowest and highest) values of the p à =s à ratio found in the SI.…”

An EELS study of the structural and chemical transformation of PAN polymer to solid carbon

“…In all the experiments the microscope was operated at low dose with the LaB 6 filament desaturated to minimize the effect of electron irradiation on the samples and optimise the energy resolution. In the energy loss near edge structure (ELNES) measurements, the threshold energy in the nitrogen K-edge spectra of PAN-based samples was accurately calibrated using a reference sample of hexagonal boron nitride (h-BN) dispersed together with the PAN-based samples [5]. An iterative gain variation program was used to measure the chemical composition for the lower heteroatom contents ($1%) [6].…”

Cubic boron nitride: Experimental and theoretical energy-loss near-edge structure

“…Specifically, the ELNES of c-BN has been presented by many authors, both theoretically 12,15,16 and experimentally. 17,18 However, the detailed agreement between the experimental and calculated c-BN ELNES spectra has not been perfectly satisfactory. Either the resolution of the experimental spectra has been insufficient to reveal all the fine structure features produced in the theoretical calculations or the theoretical spectra have not fully reproduced the experimental fine structure.…”