Modification of HOPG Surface on Irradiation by Highly Charged Ar¹¹⁺ and Xe²⁶⁺ Ions Investigated by SEM, ESR, SQUID, and Raman Measurements

Abstract

Highly oriented pyrolytic graphite (HOPG) samples were irradiated by highly charged ions Ar¹¹⁺ and Xe²⁶⁺. Scanning electron microscopy (SEM), electron spin resonance (ESR), a superconducting quantum interference device (SQUID), and Raman spectroscopy were used to investigate the effect of this irradiation. SEM observations revealed that the contrast between irradiated and unirradiated regions became discernible at a fluence of about 10¹⁴ cm^-2. On the other hand, for samples irradiated by Ar⁺ ions, a fluence of the order of 10¹⁵ cm^-2 was necessary to obtain a similar contrast to that obtained by Ar¹¹⁺ ion irradiation. This demonstrates that highly charged ions effectively enhance modification of solid surfaces. Furthermore, the ESR and SQUID measurements revealed the formation of defects and magnetization of the irradiated surface. Raman measurements were also performed to investigate the structural transformation at different fluences. [DOI: 10.1380/ejssnt.2011.241]