In-Situ Stretching Patterned Graphene Nanoribbons in the Transmission Electron Microscope

Abstract

The mechanical response of patterned graphene nanoribbons (GNRs) with a width less than 100 nm was studied in-situ using quantitative tensile testing in a transmission electron microscope (TEM). A high degree of crystallinity was confirmed for patterned nanoribbons before and after the in-situ experiment by selected area electron diffraction (SAED) patterns. However, the maximum local true strain of the nanoribbons was determined to be only about 3%. The simultaneously recorded low-loss electron energy loss spectrum (EELS) on the stretched nanoribbons did not reveal any bandgap opening. Density Functional Based Tight Binding (DFTB) simulation was conducted to predict a feasible bandgap opening as a function of width in GNRs at low strain. The bandgap of unstrained armchair graphene nanoribbons (AGNRs) vanished for a width of about 14.75 nm, and this critical width was reduced to 11.21 nm for a strain level of 2.2%. The measured low tensile failure strain may limit the practical capability of tuning the bandgap of patterned graphene nanostructures by strain engineering, and therefore, it should be considered in bandgap design for graphene-based electronic devices by strain engineering.

Highly stretchable graphene nanoribbon springs by programmable nanowire lithography

“…The maximum tensile (or compressive) strain found at the outer (or the inner) edge of the strained GNR is only 0.35% (see Fig. 6f), which is far below the fracture limit of graphene (of 2-6% 21,[32][33][34]55 ). In comparison, if the GNR width is increased to 1 μm, the local strain maxima will quickly increase by an order of magnitude to~3% (Fig.…”

“…The maximum stretchability of rigid graphene sheet or straight nanoribbons has been limited to a range of 0.4-6%. 21,[29][30][31][32][33][34]55 Patterning the graphene sheet into 2D GNR springs with a thick channel width of 20 μm extends this limit to around 10%. 56 Further elasticity improvement (to 30% 26 ) can be obtained by the formation of out-of-plane 3D graphene wrinkles on pre-strained PDMS layers, 26,27 which is, however, not fully compatible to high-density planar circuit integration.…”

“…The maximum tolerable strains of graphene sheets, reported in the literature, ranges from 1 to 3%. [30][31][32][33][34] GNRs are of the same nature, but can be engineered into two-dimensional (2D) zigzag, serpentine springs, 8,29,30 or even 3D wrinkles. 26,27 Attaching straight GNRs to pre-strained polymers has been used to enforce a 3D out-of-plane buckling to achieve a high stretching up to 30%.…”

Mechanical testing of two-dimensional materials: a brief review

“…Moreover, it is impossible to visualize the dynamic fracture processes by performing nanoindentation tests. Recently, several types of micro-/nano-mechanical testing devices have been successfully designed and developed, enabling the uniform in-plane loading on a freestanding membrane of 2D crystals [76,108,[172][173][174][175][176]. As long as selected crystals are transferred onto the testing area, their mechanical properties can be well quantified.…”

Dedicated preparation for in situ transmission electron microscope tensile testing of exfoliated graphene

“…Therefore, studies to directly measure the mechanical properties of 2D materials with their structural characteristics are needed. We proposed conducting mechanical tests through microelectromechanical systems (MEMS) devices to address these problems (Liao et al 2017;Cao et al 2016).…”