Graphene nano-Ribbons (GNRs) are one-dimensional strips of graphene where quantum confinement can open a direct bandgap. Combining the exceptional electrical properties of graphene with the one of semiconductor system represent a promising field for next generation of (opto-)electronics devices. GNRs can be fabricated in many ways, however, only bottom-up approaches offer the degree of control at the atomic level which is necessary to fully exploit their potentialities. In particular surface-assisted chemical synthesis allow to precisely fabricate GNR with well-defined size and morphology.
Here we demonstrate a novel concept of device, where chemically-synthesized GNRs are employed as the active channel and graphene as the electrodes. With respect to traditional metal contacts, the use of graphene offer the advantages of low-dimensionality and affinity with other carbon-based structures. In our devices, atomically-precise GNRs are synthesized by chemical vapor deposition on Au/mica substrate and then transferred on pre-fabricated graphene electrodes to act as active channel, avoiding any further fabrication step that could worsen the properties of the GNRs.
Firstly, we employed a continuous GNR layer as the device channel and graphene electrodes with gap sizes of few hundreds of nanometers, obtained by electron beam lithography. We demonstrate field-effect transistor device with on/off current ratio as high as 104. . Moreover, as we report, these devices are particularly appealing for opto-electronic applications and light sensors, because of their photoresponsivity as high as 6 x 105 A/W in the visible-UV range, orders of magnitude higher than pristine graphene.
Finally, by employing the electroburning technique, we fabricate graphene electrodes with gaps in the range 10-50 nm; such gaps are suitable to contact individual or few GNRs. We report a systematic study using GNR with different morphologies (nanoribbons with armchair-type edges, AGNR, and different width N, where N = 5,9,10 being the integer number of Carbon atoms across the GNR width) corresponding to different electrical properties. We show that the electrical behavior of the devices is in qualitative agreement with the expected band-gap as calculated by theory.
The result we show demonstrates the huge potentiality of these all-graphene devices for novel application in nano-electronic, photonics and sensing.
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