On the mechanism of ion-induced bending of nanostructures (original) (raw)
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Characterization of ion beam induced nanostructures
(2006) Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 244 (1), pp. 45-51.
Tailoring of nanostructures with energetic ion beams has become an active area of research leading to the fundamental understanding of ion-solid interactions at nanoscale regime and with possible applications in the near future. Rutherford backscattering spectrometry (RBS), high resolution transmission electron microscopy (HRTEM) and asymmetric X-ray Braggrocking curve experimental methods have been used to characterize ion-induced effects in nanostructures. The possibility of surface and sub-surface/interface alloying at nano-scale regime, ion-beam induced embedding, crater formation, sputtering yield variations for systems with isolated nanoislands, semi-continuous and continuous films of noble metals (Au, Ag) deposited on single crystalline silicon will be reviewed. MeV-ion induced changes in specified Au-nanoislands on silicon substrate are tracked as a function of ion fluence using ex situ TEM. Strain induced in the bulk silicon substrate surface due to 1.5 MeV Au 2+ and C 2+ ion beam irradiation is determined by using HRTEM and asymmetric Bragg X-ray rocking curve methods. Preliminary results on 1.5 MeV Au 2+ ion-induced effects in nanoislands of Co deposited on silicon substrate will be discussed.
On the fabrication of micro-and nano-sized objects: the role of interstitial clusters
Journal of Materials Science, 2018
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 9 10 21 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.
Ion-beam-induced embedded nanostructures and nanoscale mixing
(2004) Journal of Applied Physics, 96 (9), pp. 5212-5216.
Megaelectron volts ion-induced effects for discontinuous gold nanoislands and for continuous gold films on silicon substrate have been studied. Irradiation was carried out with 1.5 MeV Au2+ ions at room temperature to various fluences. Cross-sectional transmission electron microscopy and Rutherford backscattering spectrometry are used to study the ion-beam mixing in Au/Si systems. At a fluence of 1 × 1014 ions cm-2, a material push-in effect and a metastable Au-Si phase formation have been observed for Au nanoislands, while no push in or mixing has been observed for the case of continuous films. The mixed phase of Au-Si system is found to be crystalline in nature. The material push- in and ion-beam mixing effects that are observed in case of nanoislands appear to be due to combined effect of capillary driving force, ion-induced viscous flow, and ion-induced energy spike effects.
Ion Irradiation Induced Effects in Metal Nanostructures
2005
High resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectrometry (RBS) are used to study the ion induced effects in Au, Ag nanostructures grown on Si and thermally grown SiO 2 substrates. Au and Ag films (∼ 2 nm) are prepared by thermal evaporation under high vacuum condition at room temperature (RT). These films were irradiated with MeV Au ions also at RT. Very thin films of Au and Ag deposited on silicon substrates (with native oxide) form isolated nano-island structures due to the non-wetting nature of Au and Ag. Ion irradiation causes embedding of these nanoislands into the substrate. For Ag nanoislands with diameter 15 -45 nm, the depth of the embedding increases with ion fluence and the nano particles are fully submerged into Si and SiO 2 substrate at a fluence of ∼ 5×10 14 ions cm −2 without any mixing. Au nanoparticles (diameter 6 -20 nm), upon ion irradiation, forms embedded gold-silicide in the case of Si substrate and show lack of mixing and silicide formation in the case of SiO 2 substrate system.
Advanced Materials Interfaces, 2018
During ion irradiation which is often used for the purposes of band gap engineering, nanostructures can experience a phenomenon known as ion-induced bending (IIB). The mechanisms behind this permanent deformation are the subject of debate. In this work, germanium nanowires are irradiated with 30 or 70 keV xenon ions to induce bending either away from or towards the ion beam. By comparing experimental results with Monte-Carlo calculations, the direction of the bending is found to depend on the damage profile over the cross-section of the nanowire. After irradiation, the nanowires are annealed at temperatures up to 440°C triggering solid-phase epitaxial growth (SPEG) causing further modification to the deformed nanowires. After IIB, it is observed that nanowires which had bent away from the ion beam then straighten during SPEG whilst those which had bent towards the ion beam bend even more. This is attributed to differences in the mechanisms responsible for the ion-beam-induced bending in opposite directions. Thus, the results reported here give insights into the mechanisms causing the IIB of nanowires and demonstrate how to predict the evolution of nanowires under irradiation and annealing. Finally, they show that, under certain conditions, the bending can even be removed via SPEG.
Rational description of the ion-beam shaping mechanism
Physical Review B, 2012
The ion-beam-shaping mechanism is studied for several classes of nearly monodispersed metallic nanoparticles (Au, Ag, and Au 0.5 Ag 0.5). They are in the range of 3-100 nm and embedded within a silica matrix. Experimentally, we show that depending on their initial sizes, several final morphologies can be obtained: (i) spherical shapes, (ii) facetted nanoparticles, (iii) nanorods, and (iv) nanowires. In parallel, the thermal-spike model was implemented for three-dimensional anisotropic and composite media to study the evolution of the temperature profile within a nanoparticle. This way, a clear correlation is found between the deformation path followed by the nanoparticles during the irradiation and the fraction of the nanoparticle that is molten (vaporized) due to the interaction with a swift heavy ion. This allows the construction of a size-vs-shape diagram relating the initial nanoparticle size to its final morphology. This diagram is used to give a rational description of the ion-beam-shaping process for all nanoparticle dimensions as a function of the irradiation parameters.
Stress-induced curvature of focused ion beam fabricated microcantilevers
Micro & Nano Letters, 2008
Abstract Microcantilevers with very low spring constants, as required to measure the short-range Casimir force, can be fabricated by focused ion beam thinning of conventional atomic force microscope cantilevers, but the resulting beams have a stress-induced curvature. This can be explained by consideration of the implanted gallium ions and associated damage effects in the etched surface. The problem can be overcome by using a complementary etch method in which top and bottom surfaces of the microcantilever are etched by the same ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008
We report a study of the physical characteristics of the pillars of C, Pt and W grown by 10-30 keV Ga focused ion beam (FIB) as a function of Ga ion flux, and present a quantitative analysis of the elements using energy-dispersive analysis of X-rays (EDAX). All the FIB grown pillars exhibit a rough morphology with whisker like protrusions on the cylindrical surface and broadening of the base as compared to the nominal size. For a constant fluence, the height of the pillar initially increases and then reduces after going through a maximum as a function of ion flux in all the cases. The compositional analysis shows good metallic quality for Pt structures but reveals significant contamination of Ga in C and Ga and C in W structures at higher ion fluxes. Explanation to all these observations has been sought in the light of secondary ion and electron effects and the different processes involved which lead to the FIB induced deposition.