Electrohydrodynamic printing of all metal oxide electronics
AffiliationElectrical and Electronic Engineering
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2021-10-08.
© 2019 You Liang
Current design and fabrication methodologies for electronic circuits are both time consuming and prohibitively costly. The processes for building transistors and other circuit components require multiple stages including the fine patterning of metal oxide thin films which heavily rely upon etching after spin-coating or sputtering. Additionally, they require photolithography and vacuum processing. The complicated processes and their associated high initial costs are significant barriers to innovation, limit access to a few organization and restricting application to very high volume market segments. Printing has been proposed as a promising technique to address this challenge. Unfortunately, to date, these techniques are not high resolution, not uniform and only able to achieve minimum feature sizes in the tens of micrometres with the thick or organic low-k gate dielectric. Printed transistors, which are the fundamental components necessary for both analog circuits and digital logic gates, are unreliable, requiring high operating voltages whilst also exhibiting low gain and switching speeds. In this thesis, new scalable approaches towards all-printed high-performance metal oxide thin film transistors (TFT) using high-resolution electrohydrodynamic (EHD) printing process are proposed. Direct EHD micropatterning of metal oxide TFTs based on diverse precursor solutions to form semiconducting materials (Indium oxide (In2O3), In-Ga-ZnO (IGZO)), conductive metal oxide (Sn-doped In2O3 (ITO)) as well as Aluminium oxide (Al2O3) gate dielectric at a temperature as low as 350 ˚C. The fully printed TFT devices exhibit excellent electron transport characteristics (average electron mobility up to 117 cm2 V−1 s−1), negligible hysteresis, excellent uniformity and stability at low-operating-voltage and under bias stress. Furthermore, integrated logic gates such as NOT, NAND have been designed and demonstrated. All-printed-logic with individual gating and symmetric input/output behaviour is achieved, which is necessary for cascading of multiple logic stages in large-scale fabrication. We expect that our approach serves as the critical foundation for future electronics with unrivalled performance, high reliability and transparency.
Keywordselectrohydrodynamic printing; metal oxide thin film transistor; direct writing; transparent electronics
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