Nanomembrane-based vertical organic transistors showing a multi-sensing capability
Nawaz, A.; Merces, L.; de Andrade, D.M.; Camargo, D.H.S.; Bufon, C.C.B.
This work presents the development of a vertical organic field-effect transistor (VOFET) platform. The devices are processed entirely via microfabrication and photolithography techniques, in the cleanroom facilities of the Brazilian Nanotechnology National Laboratory (LNNano/CNPEM). The first novelty of our VOFET architecture stems from the utilization of rolled-up nanomembrane (NM) as the top drain electrode that promotes the formation of a soft mechanical contact with the organic semiconductor (OSC) layer and enables the incorporation of sub-50 nm thick OSC layers, corresponding to one of the shortest channels utilized in VOFETs. The second novelty is related to the judicious patterning of the intermediate source electrode with precisely identical circular or rectangular-shaped perforations. The resulting devices show conventional transistor behavior with saturated output characteristics and high output current densities (JD) of ~0.5 A/cm2 at ultra-low operating voltages (≤ 3 V). Our theoretical study reveals the dependence of current density distribution on the number of lateral facets (edges) of the source metal. This highlights the role of source electrode edges as a relevant figure-of-merit to deterministically design the source electrode and drastically improve the JD of both academically and industrially manufactured patterned-source VOFETs. Based on our results, we predict that further optimization of the spatial geometry of source-electrode can yield current densities of ~10 A/cm2. Furthermore, we have astutely exploited the use of rolled-up NM drain-electrode to demonstrate the sensing of humidity and light. Hence, in addition to the innovative vertical transistors, our device platform also brings with it great promise to advance next-generation sensor technologies.
“Edge-driven vertical organic field-effect transistors with rolled-up drain electrodes.” Nature Communications, 11, 841, (2020). DOI: 10.1038/s41467-020-14661-x.