3. ALD Al-doped ZnO Thin Film as Semiconductor and Piezoelectric Material: Process Synthesis

Since the first demonstration of an integrated circuit in 1958, the ambitious semiconductor technology has been racing for almost six decades to change the face of the Earth. Moore’s Law and the ‘virtuous cycle’ of investment, scaling and market growth have fueled the sweeping influence that the semiconductor industry now has on every aspect of our everyday lives and the global economic system. Thanks to the striking drop in the cost of computing power, from 5.52 US dollars for a single transistor in 1954 to a billionth of a dollar in 2016, countless human dreams have been realized; from the Apollo missions to the AI and social networking era. While the continued scaling of traditional complementary metal–oxide–semiconductor (CMOS) devices took over the market with its impressive progress, another paradigm of electronics has taken shape: flexible electronics. Instead of focusing on shrinking critical dimensions and reducing power consumption, the growing field of flexible electronics rather aims to leverage compliant form factors and lightweight designs to usher radically novel electronic devices into our lives. Flexible displays, electronic textiles, bio-inspired sensors, and wearable or implantable medical devices, just to name a few, are out-of-reach applications for the rigid form factor of conventional wafer-based electronics. Flexible electronics is more than just a fill-in or an alternative for where conventional electronics fall short. If the integrated circuit was the game changer of the twentieth century, then flexible electronics is the catalyst for the paradigm shift of the twenty-first century.