Abstract
Micromechanically exfoliating graphene on / substrates is commonplace for graphene researchers, but locating actual graphene flakes on these substrates is a high-effort and tiresome task. The main purpose of this work was to establish a completely automated procedure to identify those graphene flakes with as little human interaction as possible, improving on the limitations of current methods. Furthermore, automatic electrical characterization of the identified flakes was performed. The proposed micro-robotic automation sequence consists of three main steps. To start, a sample surface plane is calculated, based on multiple foci points across the substrate. Secondly, flakes on the substrate are identified in the hue, saturation, and value (HSV) color space, with an implementation to fit the measurement probe, used to avoid undersized samples and adjust the flake orientation. Finally, electrical characterization is performed based on four point probe measurements with the Van der Pauw method. Results of the successfully implemented automation sequence are presented together with flake electrical properties and validation.
Highlights
These materials are non trivial to characterize, handle, or process; and many properties are obscured due to the lithographical pre or post processing that is necessary
Other methods [4,5], e.g., chemical vapor deposition (CVD) for large area graphene fabrication and transfer procedures, do not provide the graphene quality that is expected for research tasks [6]
Micro mechanically exfoliated graphene flakes remain the best alternative for research investigations
Summary
These materials are non trivial to characterize, handle, or process; and many properties are obscured due to the lithographical pre or post processing that is necessary. Lithographical procedures induce contamination and undesired effects on the 2D materials [3]. Other methods [4,5], e.g., chemical vapor deposition (CVD) for large area graphene fabrication and transfer procedures, do not provide the graphene quality that is expected for research tasks [6]. As the preparation of high quality graphene on Si/SiO2 substrates via micro-mechanical exfoliation yields unknown flake positions, these have to be located across the whole substrate manually on a high magnification microscope. This exercise requires a high concentration and is extremely time consuming; an approach to diminish this burden would clearly benefit the further exploration of graphene device prototyping
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