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Tin dioxide electrolyte-gated transistors working in depletion and enhancement mode Irina Valitova, Marta Maria Natile, Francesca Soavi, Clara Santato, and Fabio Cicoira ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b09912 • Publication Date (Web): 03 Oct 2017 Downloaded from http://pubs.acs.org on October 5, 2017
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ACS Applied Materials & Interfaces
Tin dioxide electrolyte-gated transistors working in depletion and enhancement mode Irina Valitova1, Marta Maria Natile2, Francesca Soavi3, Clara Santato4 and Fabio Cicoira1* 1
Polytechnique Montréal, Department of Chemical Engineering, H3T 1J4, Montreal, Canada. 2
CNR-Istituto di Chimica della Materia Condensata e di Tecnologie per l’Energia, Consiglio Nazionale delle Ricerche (ICMATE-CNR) and Dipartimento di Scienze Chimiche, Università di Padova, Via F. Marzolo 1, Padova, 35131, Italy. 3
Dipartimento di Chimica “Giacomo Ciamician”, Università di Bologna, Via Selmi 2, Bologna, 40126, Italy. 4
Polytechnique Montréal, Department of Engineering Physics, H3T 1J4, Montreal, Canada. * Corresponding author:
[email protected] 1
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Abstract Metal oxide semiconductors are interesting for next generation flexible and transparent electronics due to their performance and reliability. Tin dioxide (SnO2) is a very promising material that has already found applications in sensing, photovoltaics, optoelectronics and batteries. In this work, we report on electrolyte-gated, solutionprocessed polycrystalline SnO2 transistors on both rigid and flexible substrates. For the transistor channel, we used both unpatterned and patterned SnO2 films. As decreasing the patterned area increases the charge carrier density, patterned transistors operate in depletion mode, whereas unpatterned ones operate in enhancement mode. We also fabricated flexible SnO2 transistors that operate in enhancement mode and can withstand moderate mechanical bending.
Keywords: tin dioxide, electrolyte gating, transistors, ionic liquids, patterning
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ACS Applied Materials & Interfaces
Introduction Wide band gap metal oxides, such as ZnO, In2O3, InZnO, and InGaZnO (IGZO) are promising materials for transparent and flexible transistors.1-12 The ideal application of metal oxide transistors is in display technologies, where IGZO-based backplanes have been introduced as an alternative to amorphous Si. In particular, metal oxide electrolytegated transistors are attractive for display backplanes because of their high driving current and low operation voltage. While the best performance is in principle achieved with vacuum-deposited materials, solution processing is attractive for flexible and large area electronics applications. SnO2, an abundant and low-cost material, is a wide band gap n-type (3.6 eV) oxide that is used, in its doped form, as a transparent conductor and as a solid-state gas sensing material.13-15 The high electrical conductivity of SnO2, mostly due to the tendency of this material to form oxygen vacancies,16,17 typically leads to transistor operation in depletion mode. SnO2 thin film transistors (TFTs) were reported by Klasens and later by Aoki.18,19 In 1996, Prins demonstrated Sb-doped SnO2 ferroelectric TFTs with charge carrier concentration of 1018 cm-3 and electron mobility of about 5 cm2V-1s-1. SnO2 films were obtained by pulsed laser deposition.20 A much higher electron mobility (about 158 cm2V1 -1
s ) was achieved in sputtered SnO2 TFTs, highly doped with Sb.21 Jang et al.
demonstrated solution-processed SnO2 TFTs with high electron mobility (about 100 cm2V-1s-1) and low operating voltage (
