Using lasers to tailor graphene properties
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Laser patterning has been demonstrated by AIMEN researchers working within FaiERA project, revealing control of optical and chemical properties of selective graphene area by means of picosecond laser pulse irradiation. This work will open the possibilities of high speed, industrial technologies for device production based on graphene local functionalization with lasers.
Carbon nanomaterials display extraordinary physical properties, outstanding among any other substance available, and Graphene has grown as the most promising material for brand-new electronic circuitry, sensors and optical communications devices. Graphene is a single atomic-thick sheet of honeycomb carbon lattice, with unique electronic and optical, which bring a new era of fast, reliable, low power communication and information processing.
But two problems hinder graphene´s uptake in real world electronics. There is no large-scale technology to control the properties of graphene, and the traditional technology used for silicon based processors (solid state) is not suitable for graphene processing (molecular material).
Figure 1: Locally functionalized graphene lattice by laser induced chemical modification
The researchers from Technological Center AIMEN explore the use of ultrafast lasers as tool for graphene processing. The laser beam can be focused precisely, used to tailor the properties of graphene films in finely defined areas, to produce distinct behaviours useful for producing devices.
The key is the use of short, highly controlled laser pulses, which will induce chemical changes in the carbon lattice. It’s enough a single pulse of laser, with a duration of several picoseconds – the time of a single oscillation in a polar molecule, like water. For this timescale, researches demonstrated that they can pattern graphene lattice by cutting, adding external molecules or binding compounds (functional groups like oxygen or hydroxyl). As the laser spot can be focused in areas of one square micron or less, direct writing of devices on graphene can be done with high precision, producing nano-devices with minimal footprint and maximum efficiency.
As recently published in Applied Physics Letters , the work of AIMEN researches demonstrated laser based large scale patterning of graphene at high speed and resolution, opening new possibilities for device making. The speed of process can be higher than 1 m/s for drawing the micrometer sized features. Processing speeds over 10 m/s could be attained using advanced optical scanning.
Fig. 2: Laser irradiated pattern on graphene is visible under optical microscope, revealing changes in optical properties.
Moreover, the work demonstrated the control of the thermal and chemical processes by adjusting laser beam characteristics. For low energy inputs, multiphoton absorption plays a major role, inducing chemical reactions between carbon and atmosphere molecules, resulting in new optical properties in graphene.
The potential of the altered optical properties (like spectral transmission) of functionalized graphene are just starting to be recognized, and the full industrial potential of this technology needs to be tackled. This research work lays a foundation for deep understanding of the chemical and physical processes for industrially feasible graphene patterning, as well as tests in real device application for future electronics.