(Invited) Piezotronics in 1D/2D Nanomaterials for Active and Adaptive Nano-Electronics/Optoelectronics

New technologies for developing smart electronics and optoelectronics with tunable/adaptive functionalities are critical to emerging applications in wearable technology, advanced manufacturing, renewable energy, personal healthcare and environmental monitoring, which demand the active and adaptive interactions between devices and stimuli. Non-electrical stimuli are ubiquitous and abundant in the environment, such as mechanical agitation from human body. It is however not facile to directly interface them using the state-of-the-art silicon technology, in which the fundamental components performing intelligent-bearing operations are prevalently the field-effect-transistors (FETs). Piezoelectric effect has been widely used in sensing, actuation and energy harvesting. Conventional piezoelectric materials such as PZT and PVDF are insulating and therefore not feasible for constructing functional electronics or optoelectronics. The fundamental effect of piezoelectric polarization on charge carrier processes by dynamic perturbation, which has immediate relevance to the abovementioned emerging applications, has been long overlooked. Motived by these, my research has focused on exploring the emerging piezotronic effect, which is the modulation of charge carrier process by dynamic-strain-induced polarization, for nanoscale renewable energy and novel smart electronics/optoelectronics by rational design, manufacturing and integration of nanostructured piezoelectric semiconductors, e.g. 1D ZnO nanowires and 2D single-atomic-layer MoS₂. I will discuss the fundamental of piezotronics and the updated progress of related applications. These studies provide the novel approach for modulating device characteristics by tuning the junction/contact properties, which has been unavailable in conventional technologies without modifying the interface structure or chemistry, and may open up opportunities in enabling technology advances in energy harvesting, sensing, human-machine interfacing, robotics, healthcare and more.