Graphene & 2D Systems Research @ IIT Madras: Highlights

Research Theme-1: Graphene - a flexible and elastic membrane

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* Exploring Snap-through transitions of Atom-thin Membranes with "4-dimensional Lithography" - Lithography is 3-dimensional, allowing the patterning of structures with a given lateral dimension and aspect ratio. We developed new electron-beam lithography resist patterns that swell vertically by 10-times in ambient. We study how graphene membranes adapt to the nanoscale substrate corrugation with widely tuneable aspect ratio. Read this work in detail: P R Shaina and Manu Jaiswal, 2014 Appl. Phys. Lett. 105 193103.

* Wrinkles in Graphene and the Elusive Determination of it's TEC - Most materials expand upon heating. Graphite is one material which undergoes in-plane contraction on heating at ambient temperatures and thus has a negative thermal expansion coefficient (TEC). This property of graphite is known since the 1940s. What comes as a surprise is that TEC of graphene (single-layer of graphite) is hotly contested, and not just for its magnitude but also for its sign. Our published work, P R Shaina et al 2016 J. Phys.: Condens. Matter 28 085301, explores the reason behind the literature discrepancies in graphene's TEC and conveys the importance of factoring the substrate interaction and strain profile of graphene membranes in the estimation of TEC. Wrinkles, a universal feature of thin flexible membranes that range from curtains and human skin to graphene, holds the key to understanding the TEC of graphene.

* Graphene Oxide for Flexible Electronics - Graphene oxide films are prime candidates for flexible electronics. In our work, Tushar Sakorikar et al 2017 Scientific Reports 7 2598, we demonstrate the evolution of cracks in strained GO films. In particular, tuning the geometry allows for strain-resistive and strain-responsive films. The non-trivial crack response to strain is demonstrated with morphology and electrical studies. High gauge factor strain sensors are realized as one outcome, while strain resistive electrodes are used for stable photoconductors. Low-temperature ransport anomalies at high strain are also observed, PR Shaina et al 2017 Journal of Physics: Condensed Matter 29 235301

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