Energy threshold for nanodot creation by swift heavy ions

TL;DR

This paper investigates the energy threshold necessary for creating nanodots on surfaces using swift heavy ions, combining theoretical modeling with experimental validation to identify key thresholds for track formation.

Contribution

It introduces a two-temperature model accounting for spatial electron density to predict nanodot formation thresholds, validated by experiments on SrTiO3 surfaces.

Findings

Threshold of 12 keV/nm for melting material

Identification of two thresholds for track appearance and development

Experimental thresholds align with theoretical predictions

Abstract

We present theoretical and experimental data on the threshold behaviour of nanodot creation with swift heavy ions. A model calculation based on a two-temperature model taking the spatially resolved electron density into account gives a threshold of 12 keV/nm below which the energy density at the end of the track is no longer high enough to melt the material. In the corresponding experiments we irradiated SrTiO$_3$ surfaces under grazing incidence with swift heavy ions. The resulting chains of nanodots were analyzed by atomic force microscopy. In addition, samples irradiated under normal incidence were analyzed by transmission electron microscopy. Both experiments show two thresholds, connected to the appearance of tracks and to the creation of fully developed tracks, respectively. The threshold values are similar for surface and bulk tracks, suggesting that the same processes occur at glancing and normal incidence. The experimental threshold for the formation of fully developed tracks compares well to the value obtained by the theoretical description.