# Hillock formation on CaF\_2, Al\_2O\_3, c-SiO\_2 and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss

Y Wang, C Grygiel, I Monnet, E Gruber, H Lebius, B Ban d'Etat, J Sun, Y
Zhao, Z Wang, G Xiao, et al.

► To cite this version:

Y Wang, C Grygiel, I Monnet, E Gruber, H Lebius, et al. Hillock formation on CaF\_2, Al\_2O\_3, c-SiO\_2 and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss. Journal of Physics: Conference Series, 2015, 635, pp.032005. 10.1088/1742-6596/635/3/032005. hal-03748399

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https://hal.science/hal-03748399

Submitted on 27 May 2024

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<figure><img src="image_1.png" /></figure>

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# Hillock formation on CaF\_2, Al\_2O\_3, c-SiO\_2 and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss

Y Wang, C Grygiel, I Monnet, E Gruber, H Lebius, B Ban d'Etat, J Sun, Y
Zhao, Z Wang, G Xiao, et al.

<figure><img src="image_1.png" /></figure>

To cite this version:

Y Wang, C Grygiel, I Monnet, E Gruber, H Lebius, et al. Hillock formation on CaF\_2, Al\_2O\_3, c-SiO\_2 and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss. Journal of Physics: Conference Series, 2015, 635, pp.032005. 10.1088/1742-6596/635/3/032005. hal-03748399

HAL Id: hal-03748399

https://hal.science/hal-03748399v1

Submitted on 27 May 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Hillock formation on CaF₂, Al₂O₃, c-SiO₂ and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss

Y. Y. Wang*,†, C. Grygiel#, I. Monnet#, E. Gruber*, H. Lebius#, B. Ban d'Etat#,
J. R. Sun†, Y. T. Zhao†, Z. G. Wang†, G. Q. Xiao†, F. Aumayr*

**Synopsis** For impact of very slow highly charged ions on single crystal surfaces the appearance of hillocks can be linked to a threshold in potential energy while for swift heavy ions a minimum electronic energy loss per unit length is necessary. Recent investigations on CaF₂ in the medium energy range bridge the gap between these two extreme cases. These investigations are now extended to other target materials.

Great interest has been drawn by the use of ions as possible tools for lithographic modifications or "nanostructuring" of surfaces. Investigations have shown that swift heavy ions (SHI) with kinetic energies in the MeV to GeV range can induce severe structural modifications at the surface [1] and in the bulk [2]. Individual slow highly charged ions (HCI) in the keV energy regime are also able to induce surface modifications on a nanometric scale [3]. These modifications result from the deposition of potential energy carried by HCI in the topmost surface layers or from electronic energy loss of SHI along its trajectory. In both cases several keV/nm³ are deposited within a few femtoseconds into the target's electronic system and subsequently transferred to the lattice atoms via electron-phonon coupling. This similarity between HCI and SHI was pointed out [3, 4] in order to establish a qualitative link between surface modifications by potential energy and electronic energy loss.

In the medium energy range (few MeV) hillock formation on single crystal surfaces induced by highly charged heavy ions has recently been studied. This study has shown an additive effect between depositions of kinetic energy and potential energy for surface nanostructure formation on CaF₂ [5].

We have now extended these investigations to other insulating materials including Al₂O₃, c-SiO₂ and MgO. As a first step we have irradiated these materials by 100 MeV Pb ions delivered by the IRRSUD beamline at GANIL. Because the electronic energy deposition depends on the SHI velocity [6], the impact energy of the SHI was varied by Al foil degradation.

The aim of these investigations is to find the Sₑ threshold for the SHI case. Unfortunately on several crystals the surface roughness or present surface contaminations prevented an unambiguous identification of ion-induced nanostructures. In these cases irradiation were also conducted under grazing angles of incidence. Surface tracks usually take the form of a chain of hillocks [7] and are therefore more easily identified than single ion-induced hillocks. Our results for SHI irradiation of Al₂O₃, c-SiO₂ and MgO will be presented at the conference.

This work has been supported by the French-Austrian collaboration SIISU, co-financed by ANR (France, ANR-12-IS04-0005-01) and FWF (Austria, Project No. I 1114-N20), as well as by the French-Chinese cooperation project IiN by PICS-CNRS (France) and NSFC (China, No. 11411130112).

## References

[1] R. Neumann 1999 *Nucl. Instr. Meth. B* 151 42

[2] M. Toulemonde et al 1988 *Phil. Mag. A* 58, 799

[3] F. Aumayr et al 2011 *J. Phys. Cond. Matt.* 23 393001

[4] A. El Said et al 2008 *Phys. Rev. Lett.* 100 237601

[5] Y.Y. Wang et al 2014 *Sci. Rep.* 4 5742

[6] A. Meftah et al 1993 *Phys. Rev. B* 48, 920

[7] E. Akcöltekin et al 2007 *Nature Nanotechnology* 2, 290

<figure><img src="image_2.png" /></figure>

<footnote>* Institute of Applied Physics, TU Wien, 1040 Vienna, Austria</footnote>

<footnote>† Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China</footnote>

<footnote># CIMAP-GANIL, CEA-CNRS-ENSICAEN-University of CAEN, F-14070 Caen, France</footnote>

<footnote>†¹ E-mail: ywang@iap.tuwien.ac.at</footnote>
# Hillock formation on CaF₂, Al₂O₃, c-SiO₂ and MgO single crystal surfaces by ion impact - From potential energy deposition to electronic energy loss

Y. Y. Wang*,†, C. Grygiel#, I. Monnet#, E. Gruber*, H. Lebius#, B. Ban d'Etat#,
J. R. Sun†, Y. T. Zhao†, Z. G. Wang†, G. Q. Xiao†, F. Aumayr*

**Synopsis** For impact of very slow highly charged ions on single crystal surfaces the appearance of hillocks can be linked to a threshold in potential energy while for swift heavy ions a minimum electronic energy loss per unit length is necessary. Recent investigations on CaF₂ in the medium energy range bridge the gap between these two extreme cases. These investigations are now extended to other target materials.

Great interest has been drawn by the use of ions as possible tools for lithographic modifications or "nanostructuring" of surfaces. Investigations have shown that swift heavy ions (SHI) with kinetic energies in the MeV to GeV range can induce severe structural modifications at the surface [1] and in the bulk [2]. Individual slow highly charged ions (HCI) in the keV energy regime are also able to induce surface modifications on a nanometric scale [3]. These modifications result from the deposition of potential energy carried by HCI in the topmost surface layers or from electronic energy loss of SHI along its trajectory. In both cases several keV/nm³ are deposited within a few femtoseconds into the target's electronic system and subsequently transferred to the lattice atoms via electron-phonon coupling. This similarity between HCI and SHI was pointed out [3, 4] in order to establish a qualitative link between surface modifications by potential energy and electronic energy loss.

In the medium energy range (few MeV) hillock formation on single crystal surfaces induced by highly charged heavy ions has recently been studied. This study has shown an additive effect between depositions of kinetic energy and potential energy for surface nanostructure formation on CaF₂ [5].

We have now extended these investigations to other insulating materials including Al₂O₃, c-SiO₂ and MgO. As a first step we have irradiated these materials by 100 MeV Pb ions delivered by the IRRSUD beamline at GANIL. Because the electronic energy deposition depends on the SHI velocity [6], the impact energy of the SHI was varied by Al foil degradation.

The aim of these investigations is to find the Sₑ threshold for the SHI case. Unfortunately on several crystals the surface roughness or present surface contaminations prevented an unambiguous identification of ion-induced nanostructures. In these cases irradiation were also conducted under grazing angles of incidence. Surface tracks usually take the form of a chain of hillocks [7] and are therefore more easily identified than single ion-induced hillocks. Our results for SHI irradiation of Al₂O₃, c-SiO₂ and MgO will be presented at the conference.

This work has been supported by the French-Austrian collaboration SIISU, co-financed by ANR (France, ANR-12-IS04-0005-01) and FWF (Austria, Project No. I 1114-N20), as well as by the French-Chinese cooperation project IiN by PICS-CNRS (France) and NSFC (China, No. 11411130112).

## References

[1] R. Neumann 1999 *Nucl. Instr. Meth. B* 151 42

[2] M. Toulemonde et al 1988 *Phil. Mag. A* 58, 799

[3] F. Aumayr et al 2011 *J. Phys. Cond. Matt.* 23 393001

[4] A. El Said et al 2008 *Phys. Rev. Lett.* 100 237601

[5] Y.Y. Wang et al 2014 *Sci. Rep.* 4 5742

[6] A. Meftah et al 1993 *Phys. Rev. B* 48, 920

[7] E. Akcöltekin et al 2007 *Nature Nanotechnology* 2, 290

<figure><img src="image_3.png" /></figure>

<footnote>* Institute of Applied Physics, TU Wien, 1040 Vienna, Austria</footnote>

<footnote>† Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China</footnote>

<footnote># CIMAP-GANIL, CEA-CNRS-ENSICAEN-University of CAEN, F-14070 Caen, France</footnote>

<footnote>†¹ E-mail: ywang@iap.tuwien.ac.at</footnote>