We propose new “paper transistors” with unique structure using carbon-nanotube (CNT)-composite papers for aiming to construct “paper logic circuits.” Recently, the CNT that is one of nano-carbon materials has been receiving increasing attention because it has a lot of excellent characteristics, and is expected to be applied to various objects in wide areas. In concrete, it is known that the CNT has chemical stabilities, high electrical and thermal conductivities. Especially, they show unique electrical properties, i.e., metallic and semiconducting properties that depend on their structure. However, generally, it is hard to handle the CNTs because they exist in the powder state. As a solution for it, various CNT composites have been proposed. We have also succeeded in developing unique composites by combining ordinary papers, i.e., carbon-nanotube-composite papers (CNTCPs). Our CNTCP shows many properties, e.g., electrical conductivity, resulted from contained CNTs despite a paper. Moreover, it can be metallic-CNTCPs and semiconducting-CNTCPs by choosing and containing the metallic CNTs and the semiconducting CNTs, respectively. Originally, papers are familiar materials in our daily life. Therefore, by using and applying our CNTCPs instead of the ordinary ones, the papers will be able to have electrical and electronical functions in near future. Actually, we have succeeded in developing many “paper devices,” for example “thermoelectric power generating papers” and so on. In this study, we have focused on the electrical characteristics as described above and developed “paper transistors” by combining three types of papers, i.e., metallic-CNTCPs as electrodes, semiconducting-CNTCPs as channels, ordinary papers as insulators. Each paper can be fabricated easily by using a papermaking method based on the Japanese-washi papermaking technique. In concrete, CNT aqueous dispersion and pulp (a raw material of the paper) aqueous dispersion are prepared, firstly. Then, both dispersions are mixed, contained water is drained, and remained objects are dried and formed to finalize the fabrication. When semiconducting CNTs are chosen for the dispersion in the above process for example, the fabricated CNTCPs shows a semiconducting property. In previous study, we have already succeeded in fabricated a prototype paper transistor. The first one showed a p-type characteristic because CNTs show the p-type semiconductor characteristic in the air. However, its operation was not so stable and n-type operation could not be obtained. Therefore, we here try to fabricate stable paper transistors with new structure design and the n-type paper transistors by n-type doping for CNTs. To obtain stability and improve its performance, we try to reduce contact resistance between electrodes (source and drain) and channels in our paper transistor, and choose a thinner ordinary paper as an insulator. In contrast, the way to fabricate the n-type CNTCPs is doping with crown ethers and potassium hydroxides (KOH) for CNTs. We measured fabricated samples and evaluated. As results, Vd -Id characteristics of new structure showed good performance compared to previous. Finally, we will develop p-type and n-type paper transistors, and be able to develop “paper logic circuits” by combining the two types of our paper transistors in near future.
Journal: TechConnect Briefs
Volume: 4, Informatics, Electronics and Microsystems: TechConnect Briefs 2018
Published: May 13, 2018
Pages: 47 - 50
Industry sector: Sensors, MEMS, Electronics
Topicss: Advanced Manufacturing, Nanoelectronics