Soft-Landing Ion Deposition of Isolated Radioactive Probe Atoms on Surfaces: A Novel Method

Abstract

We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass separated using an isotope separator, decelerated to 5 eV, and directly deposited on the surface. The method allows for performing hyperfine interactions experiments using trace amounts of radioactive probes located at surfaces and interfaces. The characteristics of the deposition method were studied by performing perturbed angular correlation experiments on the system In on Cu(17,1,1). The results are in agreement with molecular dynamics simulations of the deposition process. The potential of this novel technique is briefly discussed.[S0031-9007(97)03222-5]

Diffusion and incorporation of a surfactant: In on (vicinal) Cu(001)

“…[8][9][10][11][12][13]. Perturbed angular correlation spectroscopy (PACS) makes use of the anisotropic emission of c-rays of a set of excited probe nuclei with respect to the direction of their nuclear spin.…”

“…After it has been deposited, it forms a surface alloy and already works as a surfactant at coverages as low as a few percent of a monolayer [6]. The In/Cu(0 0 1) system has been studied extensively with the technique of perturbed angular correlation spectroscopy (PACS) [8][9][10][11][12][13]. The results from these studies indicate the indium atoms go through a sequence of four different sites on/in the Cu(0 0 1) surface in the course of the incorporation process: (1) an isolated In adatom on the Cu(0 0 1) terrace, the adatomic terrace site, (2) an isolated In atom residing at a kink, the adatomic step site, (3) an isolated In atom incorporated in the first row of a step, the substitutional step site and (4) an isolated In atom incorporated in a Cu(0 0 1) terrace, the substitutional terrace site.…”

“…Combining the STM results with the PACS data of Refs. [8][9][10][11][12][13], we construct a comprehensive picture for the entire incorporation process.…”

Surface and Interface Magnetism on the Atomic Scale

“…Top: An ordered structure of isolated impurities (e.g., rare earth atoms) embedded in a monolayer (e.g., Pd) on a ferromagnetic surface (e.g., Ni). Pd forms 10 13 unit cells/cm 2 on Ni of which one is shown. The impurities occupy selected sites within the unit cell.…”

“…The Groningen/Netherlands group (under the leadership of L. Niesen) developed a soft-landing procedure for probe ions by deceleration after they were mass separated in an isotope separator [10]. Applying this procedure to Ag surfaces with 111 Ag ions, they could perform PAC measurements with varying sample conditions.…”