Two-dimensional (2D) materials research was primarily limited to scientific theory and speculation until 2004 when Andre Geim and Konstantin Novoselov announced the isolation of the monolayer graphitic sheets known as graphene. This discovery proved to be catalytic for materials science research. Over the last fourteen years, more than a dozen elemental and compound crystals comprising just a single or a few atomic layers have been synthesized through novel methods, including molybdenum disulfide (MoS2) and boron nitride (BN) films.
Atomic force microscopy (AFM) has been integral in 2D materials research since Geim and Novoselov first used the technology to confirm graphene isolation. Graphene AFM imaging was conducted to determine the mechanical properties of the first graphitic sheets, demonstrating encouraging distinctions between monomolecular graphene sheets and bulk graphite. It also proved many of the theoretical electromechanical properties of 2D carbon allotropes.
Graphene AFM research enables cutting-edge material characterization, providing three-dimensional (3D) measurements of sample sheets at sub-angstrom resolutions. Initially, this was used to characterize the morphology, roughness, and uniformity of graphene samples, though at higher resolution it could also resolve the lattice structure. Over time, the cabilities of graphene AFM imaging have expanded to enable multi-faceted measurements including conductivity, permittivity, stiffness, dissipation, and viscoelastic and frictional responses of the material.
Attention in the graphene AFM research community has largely evolved from basic research to studies of how to produce and use these materials in bulk. One of the most promising techniques for large-scale 2D material synthesis is chemical vapor deposition (CVD). However, these processes tend to be difficult to develop and optimize because of dependencies on substrate morphology and chemical composition, among other variable factors.
Graphene AFM research into these devices and processing methods benefit from the same myriad nanomechanical, nanoelectrical, and functional characterization capabilities that were developed early on.
Simple detection of graphene with AFM was sufficient in 2004, but research is increasingly focussed on expanding the potential of 2D materials to the commercial scale. This requires a comprehensive analysis of sample morphologies to develop, refine, and monitor the chemical growth process to support repeatable material deposition.
CVD is perhaps the best-known technique for bulk production of 2D materials, but graphene AFM research has also proven integral for so-called top-down liquid-phase reactions. In one example, graphene AFM imaging has been used to study graphene produced by exfoliation in an ionic liquid. This has yielded incredibly vivid and valuable data that has helped scientists understand the mechanism of graphene exfoliation and the balance of factors that drive dispersion of particles against their agglomerating potential.
Asylum Research provides the highest performance tools for graphene AFM imaging and 2D materials research, with a celebrated range of atomic force microscopes suitable for innovative material characterization and process monitoring. Our AFMs extend beyond conventional performance levels, providing quantitative data regarding the electromechanical properties of samples for more robust and reliable material assessments.
Graphene AFM research is expected to grow in academic, industrial, and commercial fields in the years to come. Quantum computing, photovoltaics, supercapacitors, nanoelectromechanical devices, and many more innovative techniques are gradually inching closer to reality thanks to the ongoing research conducted using AFM.