Abstract
Two-terminal, nanoscale resistive switching devices (memristors) have been extensively studied for potential applications in memory and computing systems. Two types of devices – one with abrupt resistance change (digital) and one with incremental resistance change (analog) have been developed by choosing the proper combinations of electrode and switching materials, film stack and programming conditions. The digital devices show excellent performance metrics in terms of scalability, speed, ON/OFF ratio, endurance and retention and have been viewed as a leading candidate for future nonv-volatile memory applications as Flash-memory replacements. Detailed TEM studies have been carried out to verify the switching mechanism. Functional high-density crossbar arrays have been integrated directly on top of CMOS circuits using a back-end-of-line (BEOL) process, enabling hybrid non-volatile memory and reconfigurable circuit applications. The analog devices exhibit incremental conductance changes that are analogous to the behaviors of biological synapses. Besides the ability to emulate synaptic behaviors phenomenologically, the internal ionic dynamics of these devices allow them to implement a number of important synaptic functions realistically. These analog memristive devices are well suited for hardware-based, bio-inspired neuromorphic logic systems. Device and SPICE models based on properly chosen internal state variables have also been developed for the understanding and applications of these devices at the system level. Prototype neuromorphic circuits based on memristor arrays have been shown to be able to perform tasks such as pattern recognition in an unsupervised fashion.

Biography
Prof. Wei Lu received the B.S. degree in physics from Tsinghua University, Beijing, China, in 1996, and the M.A. and Ph.D. in physics from Rice University, Houston, Texas in 1999 and 2003, respectively. From 2003 to 2005, he was a postdoctoral research fellow at Harvard University, Cambridge, Massachusetts. In 2005, he joined the faculty of the Electrical Engineering and Computer Science Department at the University of Michigan – Ann Arbor as an Assistant Professor and is currently an Associate Professor. His research interest includes high-density memory based on two-terminal resistive devices (RRAM), memristors and memristive systems, neuromorphic circuits, aggressively scaled nanowire transistors, and electrical transport in low-dimensional systems. Prof. Lu is a co-Editor-in-Chief of Nanoscale (2013 IF 6.23), a member of the International Technology Roadmap for Semiconductors (ITRS) Emerging Research Device Working Group. He is also a co-founder of Crossbar Inc, a Silicon Valley semiconductor company with over $50M VC funding to date to develop next generation non-volatile memories.  He is a recipient of the NSF CAREER Award in 2009 and the EECS Outstanding Achievement Award in 2012. To date he has published over 60 journal papers with 5600 SCI citations and an h-factor of 30.