Highly charged ion induced nanostructures at surfaces by strong electronic excitations (original) (raw)

Ballistic versus electronic processes in ion-induced nanostructuring of ionic surfaces

Physical Review B, 2009

High-resolution noncontact atomic force microscopy in UHV has been used for characterization of KBr͑001͒ surface morphology development due to an oblique incidence of low-energy ion beams ͑4 keV He + and Ar + at 75°͒. We have found several features of the process directly related to the ionic nature of halide surfaces, such as formation of two-dimensional ͑2D͒ pits and rectangular 2D epitaxial adislands on the initially atomically flat terraces. At low bombardment fluence the evolution of the 2D pits proceeds along main surface crystallographic directions. Such behavior is typical for the electron stimulated desorption ͑ESD͒ process, well-known from electron and photon irradiation experiments. No epitaxial adislands formation by ESD or by ion impact has been reported so far. For prolonged ion bombardment surface topography transforms into a regular network of grooves and rims ͑a ripple structure͒ oriented parallel to the incident beam. Such a structure has been observed for many other materials ͑metals and semiconductors͒, with a major distinction, however, that for KBr the ripples are composed of small nanosize crystallites with a persistent long-range order of the ͑001͒ surface. We have demonstrated that the fluence threshold for a transition from a random network of 2D pits and adislands into a well-oriented crystalline nanoripple structure is directly related to the balance between the electronic and ballistic stopping of the impinging ions. The theoretical interpretation of our observations is based on an atomistic approach to the ion-solid interaction and supplementary molecular-dynamics computer simulations of a single-ion impact on flat and atomic step covered surfaces. In particular, the computer simulations demonstrate that the sputtering yield for ions impinging against the ascending step edges on the irradiated surface are much greater than the ones obtained for the descending step bombardment.

Creation of surface nanostructures by irradiation with slow, highly charged ions

2007

It has recently been demonstrated that slow (v<< 1 au) highly charged ions (HCIs) are able to generate nano-sized hillocks on cleaved CaF2 (1 1 1) surfaces. The aim of the present study was to explore whether surface nanostructures can also be formed on other target materials by the impact of slow HCIs. To this purpose, we have irradiated LiF (0 0 1), diamond-like carbon (DLC) and Au (1 1 1) with slow Xe HCIs (up to charge state 44+) from the Heidelberg electron beam ion trap.

Non-kinetic damage on insulating materials by highly charged ion bombardment

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

We have measured the damage caused by the impact of low velocity, highly charged ions on insulating surfaces. Atomic force microscopy allows us to observe directly the surface topography with nanometer resolution. Using constant velocity (100 keV) Xe q+ ions (25 ~< q ~< 50) impinging on mica, we observe damage caused by single ion impacts. Impact sites typically are circular hillocks. Within the range and accuracy of the data, the height and volume of the damaged regions are well approximated by a linear function of ion potential energy.

Characterization of ion beam induced nanostructures

(2006) Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 244 (1), pp. 45-51.

Tailoring of nanostructures with energetic ion beams has become an active area of research leading to the fundamental understanding of ion-solid interactions at nanoscale regime and with possible applications in the near future. Rutherford backscattering spectrometry (RBS), high resolution transmission electron microscopy (HRTEM) and asymmetric X-ray Braggrocking curve experimental methods have been used to characterize ion-induced effects in nanostructures. The possibility of surface and sub-surface/interface alloying at nano-scale regime, ion-beam induced embedding, crater formation, sputtering yield variations for systems with isolated nanoislands, semi-continuous and continuous films of noble metals (Au, Ag) deposited on single crystalline silicon will be reviewed. MeV-ion induced changes in specified Au-nanoislands on silicon substrate are tracked as a function of ion fluence using ex situ TEM. Strain induced in the bulk silicon substrate surface due to 1.5 MeV Au 2+ and C 2+ ion beam irradiation is determined by using HRTEM and asymmetric Bragg X-ray rocking curve methods. Preliminary results on 1.5 MeV Au 2+ ion-induced effects in nanoislands of Co deposited on silicon substrate will be discussed.

Ion irradiation and defect formation in single layer graphene

Carbon, 2009

Ion irradiation by 500keV C+ ions has been used to introduce defects into graphene sheets deposited on SiO2 in a controlled way. The combined use of Raman spectroscopy and atomic force microscopy (AFM) allowed one to clarify the mechanisms of disorder formation in single layers, bilayers and multi-layers of graphene. The ratio between the D and G peak intensities in

Graphene defects induced by ion beam

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2017

The efficiency of defect generation by atomic ions depend on ion mass and energy similarly as vacancy generation directly by ion predicted by SRIM simulations. However, efficiency of defect generation in graphene by molecular carbon ions is essentially higher than summarized efficiency of similar group of separate atomic carbon ions of the same energy that each carbon ion in a cluster. The evolution of the D/D 0 ratio of Raman lines intensities with ion fluence was observed. This effect may indicate evolution of defect nature from sp3-like at low fluence to a vacancy-like at high fluence. Observed ion graphene interactions suggest that the molecular ion interacts with graphene as single integrated object and should not be considered as a group of atomic ions with partial energy.

Surface transformation of graphite or diamond following Highly Charged Ion irradiation

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009

Highly Charged Ions (HCI) approaching surfaces at nm distances are known to extract a very large number of electrons from the target. Over dielectric surfaces, the positive holes left following the removal of the electrons cannot be immediately neutralized, thereby locally inducing a huge stress and creating permanent surface modifications on very small dots. We present in this paper experiments on the structural transformations induced by irradiation with HCI of graphite and diamond surfaces characterized using the Atomic Clock Property of the Hollow Atoms (ACPHA) technique.

Nano-structure formation due to impact of highly charged ions on HOPG

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010

Highly ordered pyrolitic graphite (HOPG) was irradiated with slow highly charged Arq+ and Xeq+ ions in a kinetic energy range of 150–360keV and has been observed by scanning probe microscopy. Nano-sized hillock-like structures are found for all charge states and kinetic energies with both the scanning tunneling microscope and the atomic force microscope. However in the latter case, the dependence of the detected structures on scan conditions points towards a surface modification which manifests itself only in frictional forces and therefore in height measurement artifacts. Furthermore the generated defects are not stable but can be erased by continuous scanning in contact mode.