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Item type:Publication, Access status: without files , Bending of nanoporous thin films under ion radiation(Elsevier, 2019-07-11); ; ; In general, fundamental understanding of radiation resistance of high surface density nanoporous materials and nanoporous coatings is severely lacking. In this contribution ion-induced bending phenomena are studied in free-standing nanoporous Au cantilevers with thickness in the range of 100 to 200 nm. Experiments were performed in a Tescan Lyra dual beam system with Ga+ ion irradiation normal to the sample surface up to a maximum fluence of ~3 × 1019 m−2. Cantilevers bend towards the incident ion beam. It was found that the sensitivity of nanoporous Au samples to radiation-induced bending is substantially higher in comparison to the solid bulk counterparts. The process is described in terms of ion-induced coarsening of the structure top layers, which generates a volume contraction responsible for the bending moment. Therefore it is concluded that radiation-induced coarsening/sintering leads to negative swelling. Radiation-modified effective Young's modulus of the top layers was shown to influence essentially the fluence dependence of bending curvature. Model predictions agree well with our experimental findings showing that inhomogeneous radiation-induced coarsening of nanoporous structure results in bending and that nanoporous materials are less suitable for coatings in nuclear applications under the test conditions.Publicationtype: Journal Article9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Size-dependent ion-induced densification of nanoporous gold(Elsevier, 2019-01-28); ; ; Relative density is a major factor governing the mechanical properties of (nano-)porous materials. In nanoporous gold, a correlation between relative density and the ligaments aspect ratio was recently reported as the result of a meta-study that measured hundreds of published images. The effects of ion-irradiation on nanoporous structures however are not yet well explored. We irradiated samples of nanoporous gold of two different initial characteristic lengths with 30 keV Ga + ions. The degree of densification was found to be higher for the samples with finer ligaments and to proceed by thickening of ligaments besides the reduction in length also observed in the coarser samples. The proportionality between relative density and aspect ratio in the ion irradiated samples was found to agree well with the previously reported results from specimens of various processing and coarsening routes. The present study points at ion irradiation as a tool to tune these parameters in nanoporous structures and suggests that the correlation between relative density and aspect ratio may be involved in the volume contraction observed during the formation of nanoporous samples by dealloying.Publicationtype: Journal Article17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the fabrication of micro- and nano-sized objects : the role of interstitial clusters(Springer, 2018-05-01); ; ; Ion-induced bending phenomena were studied in free-standing nano-sized Al cantilevers with thicknesses in the range of 89–200 nm. The objective is to present a predictive and useful model for the fabrication of micro- and nano-sized specimens. Samples were irradiated in a Tescan Lyra dual beam system with 30 kV Ga+ ions normal to the sample surface up to a maximum fluence of ~ 2 × 1021 m−2. Irrespective of thickness, all samples bent initially away from the Ga+ beam; as irradiation proceeded, the bending direction was reversed. The Al cantilever bending behavior is discussed in terms of depth-dependent volume change due to implanted Ga atoms, radiation-induced point defects and interstitial clusters. A kinetic model is designed which is based on a set of rate equations for concentrations of vacancies, interstitial atoms, Ga atoms and clusters of interstitial atoms. The bending crossover is explained by the formation of sessile interstitial clusters in a zone beyond the Ga+ penetration range. Model predictions agree with our experimental findings.Publicationtype: Journal Article28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the mechanism of ion-induced bending of nanostructures(2018-02-06); ; ; This contribution concentrates on ion-induced bending phenomena which may serve as a versatile tool to manufacture nanostructured devices. In particular bending was studied in free standing Au cantilevers. The preparation and irradiation of the cantilevers were performed using a TESCAN LYRA dual beam system. Cantilevers with thicknesses ranging between 90 and 200 nm were irradiated with 30 keV Ga ions normal to the sample surface up to a maximum fluence of ∼3 × 10 20 Ga/m 2 . The bending of the cantilevers towards the incident beam is discussed in terms of local volume change due to accumulation of radiation-induced vacancies and substitutional Ga atoms in the Ga implantation layer, as well as due to accumulation of interstitial type clusters in the region beyond the Ga penetration range. A model is proposed to explain the observations, based on a set of rate equations for concentrations of point defects, i.e. vacancies, self-interstitials and implanted Ga atoms. The influence of preexisting defects is also discussed. The work shows that an in-depth understanding the ion-beam bending can play a predictive role in a quantitative control in for the micro- and nanofabrication of small-sized products.Publicationtype: Journal Article16