Black phosphorus thin-film transistors : from strain tunability to high frequency applications
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Flexible smart systems with functionalities of sensing and wireless communication have ignited worldwide interest. The main driving force behind this is the concept of Internet of Things (IoT), where the world is reshaped via digitalizing and connecting billions of smart devices. In this dissertation, we report on our research to advance the understanding and development of two-dimensional semiconductors for high performance robust flexible nano electronics and smart nano systems. Our interdisciplinary research approach involves nano characterizations, nano fabrication integrations, device physics, circuits, and thin-film mechanics. Specifically, this dissertation is composed with detailed discussion on following experimental works. In chapter 2, we discussed the ambient degradation of few layer black phosphorus (BP) and the development of effective dielectric encapsulation methodology for enhancing the air stability. In chapter 3, we presented the first few layer BP based flexible thin-film transistors and the circuit units realized from single and double BP TFTs. In addition, strong mechanical robustness was validated for the fully functional BP amplitude modulated AM demodulator. In chapter 4, we reported the first few layer BP flexible radio frequency (RF) transistor with cut-off frequency ~20 GHz, which successfully expanded the application scenario of 2D RF devices. In chapter 5, a polymer low-k dielectric based highly stretchable substrate was developed for investigating the strain tunabilities of 2D semiconductors. For few layer BP, thickness dependence in the angle-resolved Raman intensity evolvement under tensile strain was reported the first time.