0000000001185186
AUTHOR
Mikk Antsov
Analysis of static friction and elastic forces in a nanowire bent on a flat surface: A comparative study
ZnO nanowires bent to a complex shape and held in place by static friction force from supporting flat surface are investigated experimentally and theoretically. The complex shapes are obtained by bending the nanowires inside a scanning electron microscope with a sharp tip attached to a nanopositioner. Several methods previously described in the literature are applied along with author's original method to calculate the distributed friction force and stored elastic energy in the nanowires from the bending profile. This comparative study evidences the importance of the usage of appropriate models for accurate analysis of the nanowires profile. It is demonstrated that incomplete models can lea…
Elasticity and yield strength of pentagonal silver nanowires: In situ bending tests
This paper reports in situ mechanical characterization of silver nanowires (Ag NWs) inside a scanning electron microscope using a cantilevered beam bending technique. Measurements consisted in controlled bending of a cantilevered NW by the tip of an atomic force microscope glued to the force sensor. Relatively high degree of elasticity followed by either plastic deformation or fracture was observed in bending experiments. Experimental data were numerically fitted into the model based on the elastic beam theory and values of Young modulus and yield strength were extracted. Measurements were performed on twenty Ag NWs with diameters from 76 nm to 211 nm. Average Young modulus and yield streng…
Mechanical properties of sol–gel derived SiO2 nanotubes
The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values…
Complex tribomechanical characterization of ZnO nanowires: nanomanipulations supported by FEM simulations
In the present work, we demonstrate a novel approach to nanotribological measurements based on the bending manipulation of hexagonal ZnO nanowires (NWs) in an adjustable half-suspended configuration inside a scanning electron microscope. A pick-and-place manipulation technique was used to control the length of the adhered part of each suspended NW. Static and kinetic friction were found by a 'self-sensing' approach based on the strain profile of the elastically bent NW during manipulation and its Young's modulus, which was separately measured in a three-point bending test with an atomic force microscope. The calculation of static friction from the most bent state was completely reconsidered…
Mechanical characterisation of pentagonal gold nanowires in three different test configurations: A comparative study.
Abstract Mechanical characterisation of individual nanostructures is a challenging task and can greatly benefit from the utilisation of several alternative approaches to increase the reliability of results. In the present work, we have measured and compared the elastic modulus of five-fold twinned gold nanowires (NWs) with atomic force microscopy (AFM) indentation in three different test configurations: three-point bending with fixed ends, three-point bending with free ends and cantilevered-beam bending. The free-ends condition was realized by introducing a novel approach where the NW is placed diagonally inside an inverted pyramid chemically etched in a silicon wafer. In addition, all thre…
Manipulation of nanoparticles of different shapes inside a scanning electron microscope
In this work polyhedron-like gold and sphere-like silver nanoparticles (NPs) were manipulated on an oxidized Si substrate to study the dependence of the static friction and the contact area on the particle geometry. Measurements were performed inside a scanning electron microscope (SEM) that was equipped with a high-precision XYZ-nanomanipulator. To register the occurring forces a quartz tuning fork (QTF) with a glued sharp probe was used. Contact areas and static friction forces were calculated by using different models and compared with the experimentally measured force. The effect of NP morphology on the nanoscale friction is discussed.
Metal nanodumbbells for nanomanipulations and tribological experiments
Nanomanipulation experiments were carried out on nanodumbbells (NDs) to study their kinetic behavior and tribological properties. Ag, Au and Cu NDs were produced by laser-induced melting of corresponding nanowires (NWs). NDs were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Manipulation experiments were performed first with atomic force microscope (AFM) at ambient conditions, and then inside SEM at high vacuum conditions. Different regimes of motion were observed. In-plane and out-of-substrate-plane rotation were identified as the most preferred motion types of NDs.
The effect of heat treatment on the morphology and mobility of Au nanoparticles
This work was supported by The Centre National de la Recherche Scientifique (CNRS) of France and the French Embassy Program. The authors are also grateful for partial support by COST Action CA15216, the Estonian Science Foundation (grants PUT1689 and PUT1372), the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, grant 2014-2020.4.01.15.0016 and Latvian Science Council grant lzp-2018/2-0083.
Investigating the mechanical properties of GeSn nanowires.
Germanium tin (GeSn) has been proposed as a promising material for electronic and optical applications due to the formation of a direct band-gap at a Sn content >7 at%. Furthermore, the ability to manipulate the properties of GeSn at the nanoscale will further permit the realisation of advanced mechanical devices. Here we report for the first time the mechanical properties of GeSn nanowires (7.1-9.7 at% Sn) and assess their suitability as nanoelectromechanical (NEM) switches. Electron microscopy analysis showed the nanowires to be single crystalline, with surfaces covered by a thin native amorphous oxide layer. Mechanical resonance and bending tests at different boundary conditions were use…
Effect of cobalt doping on the mechanical properties of ZnO nanowires
Abstract In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases were close to theoretical strength indica…
Some aspects of formation and tribological properties of silver nanodumbbells.
In this paper, metal nanodumbbells (NDs) formed by laser-induced melting of Ag nanowires (NWs) on an oxidized silicon substrate and their tribological properties are investigated. The mechanism of ND formation is proposed and illustrated with finite element method simulations. Tribological measurements consist in controllable real-time manipulation of NDs inside a scanning electron microscope (SEM) with simultaneous force registration. The geometry of NDs enables to distinguish between different types of motion, i.e. rolling, sliding and rotation. Real contact areas are calculated from the traces left after the displacement of NDs and compared to the contact areas predicted by the contact m…
Shape restoration effect in Ag-SiO2 core-shell nanowires.
The combination of two different materials in a single composite core–shell heterostructure can lead to improved or even completely novel properties. In this work we demonstrate the enhancement of the mechanical properties of silver (Ag) nanowires (NW) achieved by coating them with a silica (SiO2) shell. In situ scanning electron microscope (SEM) nanomechanical tests of Ag–SiO2 core–shell nanowires reveal an improved fracture resistance and an electron-beam induced shape restoration effect. In addition, control experiments are conducted separately on uncoated Ag NWs and on empty SiO2 shells in order to gain deeper insight into the peculiar properties of Ag–SiO2. Test conditions are simulate…
Real-time manipulation of ZnO nanowires on a flat surface employed for tribological measurements: Experimental methods and modeling
Elastic and tribological properties of zinc oxide nanowires (NWs) on Si wafer and highly oriented pyrolytic graphite (HOPG) are experimentally investigated and theoretically interpreted. Measurements are performed inside a scanning electron microscope (SEM) using real-time manipulation technique that enables two possible ways of data registration: “external” force registration with quartz tuning fork (QTF) based sensor and “internal” force registration utilizing in situ observed elastic deformation of NWs. Young modulus is determined by loading half-suspended NW at its free end and then employed for the following tribological experiments. Maximal static friction force is estimated when NW i…
Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods
Size distribution, Young&rsquo
Colorimetric gas detection by the varying thickness of a thin film of ultrasmall PTSA-coated TiO2 nanoparticles on a Si substrate
Financial support from the Estonian Research Council (IUT2-25, PUT170, PUT1096, PUT748, PUTJD680), the Estonian Centre of Excellence in Research Projects “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (2014-2020.4.01.15-0011), “Emerging orders in quantum and nanomaterials” TK134 and the Development Fund of the University of Tartu, are all gratefully acknowledged.
Structural factor in bending testing of fivefold twinned nanowires revealed by finite element analysis
In this study, we performed finite element method simulations to investigate the effect of the structure on the elastic response of Ag and Au nanowires (NWs) with a fivefold twinned crystal structure in bending tests. Two different models of a pentagonal NW were created: a 'uniform model' having an isotropic continuous structure and a 'segmented model' consisting of five anisotropic domains. Two asymmetrical mechanical test configurations were simulated: cantilevered beam bending and 3-point bending. The dimensions of the NW, the test configurations, as well as the force and the displacement ranges were based on the previously obtained experimental data. The results of the simulations demon…
Enhanced flexibility and electron-beam-controlled shape recovery in alumina-coated Au and Ag core–shell nanowires
The proper choice of coating materials and methods in core–shell nanowire (NW) engineering is crucial to assuring improved characteristics or even new functionalities of the resulting composite structures. In this paper, we have reported electron-beam-induced reversible elastic-to-plastic transition in Ag/Al2O3 and Au/Al2O3 NWs prepared by the coating of Ag and Au NWs with Al2O3 by low-temperature atomic layer deposition. The observed phenomenon enabled freezing the bent core–shell NW at any arbitrary curvature below the yield strength of the materials and later restoring its initially straight profile by irradiating the NW with electrons. In addition, we demonstrated that the coating effic…
Adhesion and mechanical properties of PDMS-based materials probed with AFM: A review
This work was supported by Russian Science Foundation project grant 18-19-00645 "Adhesion of polymer-based soft materials: from liquid to solid-.