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%0 Thesis
%A Piacentini, Agata
%T Flexible complementary metal oxide semiconductor logic circuits based on 2D transition metal dichalcogenides
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Dissertation
%C Aachen
%M RWTH-2025-05177
%P 1 Online-Ressource : Illustrationen
%D 2024
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2025
%Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2024
%X Two-dimensional materials have emerged as promising candidates for a wide range of potential future applications in electronics owing to their exceptional electrical, optical, and mechanical properties. Besides graphene, many other 2D materials are being investigated, such as hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs). They are crystalline materials consisting of a single or a few layers of atoms with strong in-plane atomic bonding and weaker bonding along the out-of-plane direction. In particular, TMDCs have attracted attention for thin-film transistor (TFT) technology. TMDCs like molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) exhibit unique electronic properties, including a bandgap, a crucial requirement for TFT operation. Furthermore, their atomic-scale thickness enables flexibility, making them ideal for flexible electronics. Research into TMDC-based TFTs aims to optimize their electrical properties, enhance device stability, and develop scalable manufacturing processes, opening up the possibility for the next generation of lightweight and flexible electronics. TMDCs offer a pathway to high-performance TFTs, with potential applications like flexible displays, sensors, and wearable devices. In this PhD thesis, the potential of TMDC transistors for CMOS applications in flexible electronics is explored. Specifically, MoS₂ and WSe₂ were utilized as n- and p-type channels for metal-oxide-field-effect transistors (MOSFETs), respectively. Achieving proper CMOS operation necessitates stable operation of both n- and p-type FETs. An innovative scalable encapsulation method for MoS₂-FETs, utilizing h-BN monolayers as barrier layers between each Al₂O₃ and MoS₂ interface, was investigated. This heterostructure demonstrated a reduction in n-doping induced by Al₂O₃ encapsulation, along with decreased hysteresis for ultra-slow sweeping times, attributed to an improved dielectric interface. Several contact metals were tested to optimize p-type conduction in WSe₂-FETs, with palladium top contacts emerging as superior, showcasing better FET performance (higher mobility and currents levels). After the fabrication of TFT on a flexible foil, the flexibility of these devices was evaluated under various levels of strain, enduring up to 3000 bending cycles without significant degradation. Once n- and p-type transistors were obtained, they were externally connected to realize CMOS inverters, fundamental building blocks for both digital and analogue electronics. These inverters exhibited excellent performance, demonstrating ideal switching behaviour with high gain (up to 100), high noise margin (0.87 VDD), and low average static power consumption (40 pW). These results surpass previous TMDC-based flexible inverters. A scalable process for integrating two different 2D materials on the same foil was then also developed and used for realizing more complex circuits. Inverters, ring oscillators, transmission gates, and multiplexers (2:1 MUX and 4:1 MUX) were successfully demonstrated on both rigid and flexible substrates, showing no major differences in functionality for both substrates. The remarkable performance achieved by these circuits marks a significant advancement in highlighting the potential of TMDCs as promising candidates for flexible electronic circuits.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2025-05177
%U https://publications.rwth-aachen.de/record/1012795