Abstract: Nanoscale electronic devices and biological circuit elements such as neurons are ‘pathologically’ nonlinear in their current-voltage behavior. In 1963 Ridley postulated that, under appropriate biasing conditions, a system that exhibits either a current-controlled or a voltage-controlled negative differential resistance (NDR) will bifurcate, via entropy-production-maximization, to form regions with different current-densities or electric-fields, respectively. The ensuing discussions in the non-equilibrium statistical mechanics community, however, failed to agree on the specific mechanisms causing such bifurcations. Using thermal and chemical spectro-microscopy, my group directly imaged current-density- and electric-field-bifurcations in metal oxides that are being used to implement threshold resistance switching in memristors and neuro-mimetic devices. We found that nonlinear dynamical circuit theory, which is admittedly an approximation to Maxwell’s equations, and the principle of local activity successfully predict chaotic behavior and both current-density- and electric-field-bifurcations, as well as provides a mechanism for why the bifurcations occur. We determined that upon bifurcations, internal enthalpy in the device reduces despite unchanged power input and heat output, thus suggesting an important thermodynamic constraint required to model the operations of nonlinear electronic devices. Our results explain the electroforming process that initiates nonvolatile switching in some metal oxides, and has significant implications for properly modeling any semiconductor device, since bifurcation can occur for many types of activated processes. Standard multi-physics modeling packages can quantitatively approximate the total static current flowing in a circuit, but qualitatively predict incorrect static and dynamic behavior if a bifurcation has occurred. This has significant implications for understanding the operation and the lifetime/reliability of nonlinear electronic devices.
Biosketch: R. Stanley Williams is a Senior Fellow and Senior Vice President at Hewlett Packard Labs in Palo Alto, CA. For the past 40 years, his primary scientific research has been in the areas of solid-state chemistry and physics and their applications to technology. This has taken him on a journey that began with surface science; expanded to electronic, photonic and ionic nanotechnologies; and now encompasses computation, chaos, complexity and neuroarchitectonics.
Williams joined HP Labs in 1995 to found the Quantum Science Research group, which originally focused on fundamental scientific researchatthenanometerscale.
In 2008, a team of researchers he led announced that they had built and demonstrated the first intentional memristor, the fourth fundamental electronic circuit element predicted by Prof. Leon Chua in 1971. In 2010, he received the HP CEO’s Award for Innovation for his work in sensing solutions (CeNSE, the Central Nervous System for the Earth). Beyond HP, Williams has received widespread recognition for business, scientific and academic achievement, including being named one of the top 10 visionaries in the field of electronics by EETimes, the 2014 IEEE Outstanding Engineering Manager Award, the 2009 EETimes Innovator of the Year ACE Award, the 2007 Glenn T. Seaborg Medal for contributions to Chemistry, the 50th Anniversary Laureate Lecturer on Electrical and Optical Materials for the TMS, the 2004 Herman Bloch Medal for Industrial Research, the inaugural Scientific American 50 Top Technology leaders in 2002, and the 2000 Julius Springer Award for Applied Physics. He was a co-organizer and co-editor of the workshop and book “Vision for Nanotechnology in the 21st Century”, respectively, that led to the establishment of the U. S. National Nanotechnology Initiative in 2000.
Prior to HP, Williams was a member of the technical staff at AT&T Bell Labs and a professor in the department of chemistry at UCLA. He holds over 220 US patents with ~80 patent applications pending, more than 200 patents outside the US, over 430 papers published in reviewed scientific journals, and he has written several articles for technical, business and general interest publications (including Scientific American, IEEE Spectrum, Physics Today and Harvard Business Review). Williams received his B.A. in chemical physics from Rice University and his Ph.D. in physical chemistry from the University of California, Berkeley.
For a list of publications and patents, see http://scholar.google.com/citations?user=dAFE2L8AAAAJ&hl=en
Date(s) - Mar 07, 2018
3:00 pm - 4:00 pm