Ejection of Nanoclusters from Gold Nanoislet Layers by 38 keV Au Ions in the Elastic Stopping Mode

Abstract

Total absolute yields of the ejected gold were obtained regardless of the type of the particles are--atoms, clusters, nanoclusters,--as well as absolute yields of gold nanoclusters, from nanoislet gold targets under bombardment by monoatomic gold ions at 45 degrees to the target surface with the energy 38 keV, i.e., in the "purely" elastic stopping mode -6 keV/nm up to the fluence of 4 x 10(12) cm2. Three targets had gold nanoislets on the substrate surface: 2-12 nm; -18 nm; -35 nm, the most probable sizes being 7.1; 9.4; 17.5 nm respectively. The part of the surface area covered with gold was known. Total transfer of gold was determined by means of the neutron-activation analysis and decreased from 450 to 20 at/ion. The number of the ejected gold nanoclusters was determined using TEM and decreased from approximately 0.06 to < 0.01 per one 38 keV Au ion with the increase of the most probable sizes of the nanoislets on the target from 7.1 to 17.5 nm. The yields appeared to be surprisingly high, which is of scientific and practical importance. Tentative estimations were made using molecular dynamics simulations.

Desorption of gold nanoclusters from gold nanodispersed targets by 200keV Au5 polyatomic ions in the elastic stopping mode: Experiment and molecular-dynamics simulation

“…Similar experiments with the corresponding sets of NI Au targets, measuring the same parameters were made with 1 MeV (200 keV/atom) Au 5 ions [2], i.e. with 5 times lower energy than in [1], and with $38 keV Au 1 ions [3], where the total energy losses for elastic stopping were 95%, for inelastic losses -5%, the limiting size and the total range of the ejected Au NCs being 14 nm. Several other investigations referring to the elastic stopping mode should also be mentioned.…”

“…Such models are based on: (1) the shock-wave, which might be generated by a 200 keV Au 5 ion impact on the NI or on the substrate -this might be called a ''trampoline effect" [22]; (2) the ''lift-effect", which considers intact ejection of NI to occur by the collective momentum imparted by substrate atoms sputtered by a 200 keV Au 5 ion which entered the substrate under a nanoislet [23]; 3) the ''recoil effect" discovered in [24]. It means that when under a non-central impact of a 200 keV Au 5 ion on a NI hundreds of Au atoms get knocked out towards the substrate, a recoil momentum is imparted to the rest of the NI and accelerates it away from the substrate.…”

“…It means that when under a non-central impact of a 200 keV Au 5 ion on a NI hundreds of Au atoms get knocked out towards the substrate, a recoil momentum is imparted to the rest of the NI and accelerates it away from the substrate. However, it was shown in [24] that heavy gold NIs may not be shaken off by light carbon ions as a result of the shock wave (trampoline effect); for the same reason the lift-effect [23] does not work either in the carbon substrate (15-20 nm), on which heavy Au NIs of targets ##1-5 lie. These questions are considered in detail in [24].…”

“…However, it was shown in [24] that heavy gold NIs may not be shaken off by light carbon ions as a result of the shock wave (trampoline effect); for the same reason the lift-effect [23] does not work either in the carbon substrate (15-20 nm), on which heavy Au NIs of targets ##1-5 lie. These questions are considered in detail in [24]. The ''recoil" effect was calculated using a classical molecular-dynamics method in [24] for 6 nm NIs.…”

“…These questions are considered in detail in [24]. The ''recoil" effect was calculated using a classical molecular-dynamics method in [24] for 6 nm NIs. This channel was found to provide a 10% ejection probability of NIs when 72 keV Au 400 ions penetrate the nanoislets.…”