Multi-characterization of electron-induced defects in highly oriented pyrolytic graphite

Abstract

Engineering the properties of materials through defects is at the forefront of research in Materials Science. Here, we investigate the defects produced on highly oriented pyrolytic graphite (HOPG) samples irradiated with 25 keV electrons at different doses. Our samples are characterized using micro-Raman spectroscopy, small angle X-ray scattering and atomic force microscopy measurements. We assign the D mode appearance in Raman spectra to defect-like features, which induce distortions in the electronic density of HOPG after electron irradiation. These defect-like structures are interpreted in terms of a phenomenological model previously proposed by other authors. Furthermore, magnetic measurements allow to follow the changes in the magnetization of electron-irradiated HOPG. Our results show a slight increment in coercivity in irradiated samples as well as a large remanence and saturation enhancement in the sample with higher electron irradiation dose. These novel results hint that a threshold dose needs to be overcome in order to observe a magnetic response in HOPG with electron-induced defects.