Graphite under non-hydrostatic conditions

Abstract

The combination of Raman spectroscopy and high-pressure techniques provides a unique method for studying the mechanical and structural response of carbon-based materials. Existing Raman studies on graphite under pressure were restricted to the analysis of the so-called G band, because the Raman signal from the diamond anvils overlaps other characteristic Raman features, like the D band. Here, we present a Raman spectroscopy study of highly oriented pyrolytic graphite (HOPG) under uniaxial stress using moissanite anvils. The use of moissanite has allowed us to observe, for the first time, the evolution of the D band under extreme compression. We have employed several excitation wavelengths: 632.8, 532.0 and 488.0 nm, to further study dispersion effects. Our results have important implications on the interpretation of high-pressure Raman results on several families of carbon-based compounds.

Keywords:

• highly oriented pyrolytic graphite
• Raman spectroscopy
• uniaxial stress
• moissanite anvil cell

Acknowledgements

This work was supported by MEC under the projects MALTA CONSOLIDER-Ingenio 2010 CSD2007-00045 and MAT2006-13548-C02-01. The authors acknowledge additional support from Comunidad Autónoma de Madrid under project CCG07-UCM/MAT–2403. Elena del Corro acknowledges the Spanish government for the award of a FPU PhD grant. Jesús González acknowledges support from the University Complutense under the Visitantes Distinguidos Program.