Abstract
Focused Ion Beam (FIB) is one of the most common methods for nanodevice fabrication. However, its implications on mechanical properties of polymers have only been speculated. In the current study, we demonstrated flexural bending of FIB-milled epoxy nanobeam, examined in situ under a transmission electron microscope (TEM). Controllable displacement was applied, while real-time TEM videos were gathered to produce morphological data. EDS and EELS were used to characterize the compositions of the resultant structure, and a computational model was used, together with the quantitative results of the in situ bending, to mechanically characterize the effect of Ga+ ions irradiation. The damaged layer was measured at 30 nm, with high content of gallium (40%). Examination of the fracture revealed crack propagation within the elastic region and rapid crack growth up to fracture, attesting to enhanced brittleness. Importantly, the nanoscale epoxy exhibited a robust increase in flexural strength, associated with chemical tempering and ion-induced peening effects, stiffening the outer surface. Young’s modulus of the stiffened layer was calculated via the finite element analysis (FEA) simulation, according to the measurement of 30 nm thickness in the STEM and resulted in a modulus range of 30–100 GPa. The current findings, now established in direct measurements, pave the way to improved applications of polymers in nanoscale devices to include soft materials, such as polymer-based composites and biological samples.
Highlights
With the increased demand for micro- and nano-scale devices, such as microelectromechanical systems (MEMS), more development is put into the study of the mechanical properties of materials in decreased length-scales
We propose a quantitative mechanical testing in situ Transmission Electron Microscope (TEM), which allows a simultaneous collection of mechanical data with real-time structural images
Fractures are mainly carried by dislocations, which can be traced by the TEM during the deformation process
Summary
With the increased demand for micro- and nano-scale devices, such as microelectromechanical systems (MEMS), more development is put into the study of the mechanical properties of materials in decreased length-scales. To promote these studies, advanced small-scale mechanical testing methods are used, which can isolate features of interest in the sample and measure them separately. A powerful method for investigating the mechanical properties of small-scale specimens is by quantitative mechanical testing in situ Transmission Electron Microscope (TEM). This method allows a simultaneous collection of mechanical data with real-time structural images, thereby connecting material structure and properties. One of the most prevalent methods for nanometric samples’ fabrication is the focus ion beam (FIB) milling, most commonly with a gallium ion source (Ga+)
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