Ultra-thin graphene–polymer heterostructure membranes

Abstract

The fabrication of arrays of ultra-thin conductive membranes remains a major challenge in realising large-scale micro/nano-electromechanical systems (MEMS/NEMS), since processing-stress and stiction issues limit the precision and yield in assembling suspended structures. We present the fabrication and mechanical characterisation of a suspended graphene-polymer heterostructure membrane that aims to tackle the prevailing challenge of constructing high yield membranes with minimal compromise to the mechanical properties of graphene. The fabrication method enables suspended membrane structures that can be multiplexed over wafer-scales with 100% yield. We apply a micro-blister inflation technique to measure the in-plane elastic modulus of pure graphene and of heterostructure membranes with a thickness of 18 nm to 235 nm, which ranges from the 2-dimensional (2d) modulus of bare graphene at 173 ± 55 N m to the bulk elastic modulus of the polymer (Parylene-C) as 3.6 ± 0.5 GPa as a function of film thickness. Different ratios of graphene to polymer thickness yield different deflection mechanisms and adhesion and delamination effects which are consistent with the transition from a membrane to a plate model. This system reveals the ability to precisely tune the mechanical properties of ultra-thin conductive membranes according to their applications.

Hidden Area and Mechanical Nonlinearities in Freestanding Graphene

“…It should be noted that the fits are not perfect indicating that there are facets of our experimental data not accounted for by the model. Possible reasons for deviations include: non-uniform stress fields, non-random wrinkle distribution, deviation of the geometry from perfectly circular, and possible presence of contaminants [49,50].…”

Polymer-Assisted Pressure Sensor with Piezoresistive Suspended Graphene and Its Temperature Characteristics

“…To reduce the cracks and collapse of graphene, we introduced a polymer-assisted graphene¯lm transfer method in which a layer of 50 nm-thick PMMA was spin coated on graphene to act as a structural support. 23 PMMA with excellent°exibility can not only strengthen the graphene¯lm, but also isolate it from the harmful ambient environment that would deteriorate its quality. The graphene/PMMA¯lm was obtained and transferred to our substrate by following the commonly used method in Ref.…”

“…In this work, by utilizing the°exibility and strength of a poly-methyl methacrylate (PMMA) lm, we propose a polymer-assisted pressure sensor with piezoresistive suspended graphene that provides both a relatively good pressure-sensing performance and high yield. 23 Electrical measurements were carried out in a nitrogen environment to characterize its performance, and temperature cycling tests were performed to reveal its temperature characteristics, which opens up the possibilities of highly precise pressure sensing.…”

Capacitive pressure sensing with suspended graphene–polymer heterostructure membranes

“…Most recently, graphenepolymer heterostructure membranes comprising single-layer CVD graphene and an ultra-thin polymer layer, 10s of nanometres in thickness, have been shown to provide an excellent support for facilitating suspended graphene devices with 100% yield. 35 Whilst the presence of a polymer on the surface of graphene is often a disadvantage in chemical and biomedical sensing applications (where a clean surface of graphene is crucial to providing a high sensitivity), 36 as a mechanical component it provides an optimal trade-off between the elastic modulus and membrane yield. 37 Further, a route towards minimising membrane stiction in NEMS switches is to reduce the gate electrode contact area by implementing 3-dimensional gate electrode geometries.…”