Surface science using radioactive ions at ISOLDE: from metal surfaces to two-dimensional materials

Abstract

We review the research carried out using the apparatus for surface physics and interfaces (ASPIC), at ISOLDE, CERN. We give an overview of the research highlights since 2000, focusing on magnetic and non-magnetic metallic surfaces, and introduce the scientific program that will follow the upgrade which is currently underway, focusing on two-dimensional materials. ASPIC was formerly used for the growth of ultrathin metallic films and their characterization by means of perturbed angular correlation spectroscopy. Past research has mainly focused on the determination of the magnetic hyperfine field at the probe atom located on different sites at the surface such as terraces, kinks, steps as well as on the investigation of the static magnetic polarization at the interface between ferromagnetic and paramagnetic layers. Future research on two-dimensional materials using ASPIC is foreseen to focus on the investigation of structural and electronic properties of adatoms (adsorption sites, hybridization effects, intra-atomic charge transfer, magnetic moments, etc). We emphasize, in this context, the exceptional capabilities of ASPIC in terms of broad applicability, high precision and low detection limits.

Introducing Ultra-Low Energy Ion Implantation of Radioactive Isotopes at ISOLDE, CERN for (Near-)Surface Characterization: The ASPIC and ASCII Vacuum Chambers

“…In this way, the ions are deposited onto the sample surface with thermal energy (i.e., E ≤ 10 eV). Although this method successfully incorporated PAC isotopes at the surface or interface [2,3], it had a number of drawbacks, most noticeably the inability to carefully control the energy of the deposited ions. Indeed, to place the probes at an interface, this system relied on the post-implantation growth of films in the ASPIC chamber.…”

“…To meet those challenges, the apparatus for surface physics and interfaces at CERN (ASPIC) was developed. Since the 1980's, the ASPIC has performed several experiments in ISOLDE, CERN, which have successfully brought insight into various nanostructures, such as the magnetic hyperfine field at different surface sites of metal films, or magnetic polarization at the interface between ferromagnetic and paramagnetic layers [2,3]. However, due to lack of financial support, the experimental setup became unused for more than a decade.…”

TDPAC Studies of Local Defects and Phenomena in Ferroics and Multiferroics

“…Moreover, the probes do not necessarily have to be implanted to be incorporated into the crystal lattice and can also be diffused [15] or incorporated during the sample preparation process [16]. A surface and interface study is also possible [17,18], and may be particularly interesting for the local investigation of 2D materials.…”