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 Ar 11+ and Xe 26+. 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 10 14 cm −2. On the other hand, for samples irradiated by Ar + ions, a fluence of the order of 10 15 cm −2 was necessary to obtain a similar contrast to that obtained by Ar 11+ 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.

ESR Measurements of HOPG Irradiated with Highly Charged Ions

“…From the present experiment and the previous study [10], it is supposed that magnetic modification by HCIs appears in smaller fluence than by monovalent ions. Actually, SQUID measurements indicate that HOPG samples irradiated with Ar 11+ at the fluence in the order of 10 14 ions/cm 2 have greater magnetizations than samples irradiated with monovalent ions at the fluence of 1.875 × 10 17 ions/cm 2 as in Ref.…”

“…A Lorentzian line (L1 line) appeared at low temperatures in higher resonance field. The L1 line decreases with increasing temperature and this line was not observed in measurement of unirradiated HOPG sample [10]. Because unpaired electrons result in ESR signal, it is considered that the L1 line is originated from defects (dangling bonds) formed by Ar Figure 4 shows ESR spectra and Fig.…”

“…When a proton was injected, resonance peak due to the ion injection was observed at the fluence of 10 16 cm −2 . ESR measurements of HOPG irradiated with Ar 11+ were performed in the previous study and two lines were observed in the ESR spectra at the low temperature region, however, little is known about the dependence of ESR spectra on charge state and fluence [10].…”

Observation of light and secondary ion emissions from surfaces irradiated with highly charged ions

“…We have developed an electron beam ion source at Kobe University (called Kobe EBIS) to produce HCIs and have performed various studies on the interaction of HCIs with surfaces. [6][7][8][9][10][11][12] The fluence of incident HCIs used in these experiments was in the range of 10 12 -10 14 ions/cm 2 . We have previously reported on the emission of Balmer lines that are induced by the irradiation of a surface with HCIs.…”

Electric characteristics of multi-walled carbon nanotubes irradiated with highly charged ions

“…10) Therefore, it is possible to minimize the influence of irradiation on subsurface layers using slow HCIs. We studied the structural modifications of various surfaces irradiated with HCIs through scanning tunneling microscopy, 10,11) scanning electron microscopy (SEM), [12][13][14] atomic force microscopy, 15) and Raman spectroscopy. 14) We also investigated magnetic modification on a graphite surface by electron spin resonance.…”