Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10672451 | Ultramicroscopy | 2015 | 8 Pages |
Abstract
Surfaces of InP were bombarded by 1.9 keV Ar+ ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1Ã1017 cmâ2 to 3Ã1018 cmâ2 and ion flux densities f of (0.4â2)Ã1014 cmâ2 sâ1 were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with nâ¤11.
Related Topics
Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
Hubert Gnaser, Tobias Radny,