(Invited) Direct Physical Understanding in Memristive Devices and Corresponding Device Models

Nanoscale devices composed of transition metal-oxide layers exhibiting a prominent resistance change (memristors) have been extensively researched for their technological potential. The mechanism for the reversible resistance change in these systems involves an interaction of many physical effects including electrochemistry, ion motion driven by electric fields and concentration gradients, and interactions with thermal effects. While a complete physical understanding is still in development, I will describe some of the insights gained from direct measurements using structurally and chemically-sensitive techniques with nanoscale resolution such as x-ray spectromicroscopy. Specifically, I will show recent studies utilizing scanning transmission x-ray microscopy (STXM) to observe oxygen migration in a working tantalum oxide memristor device. I will also describe ongoing work utilizing hard x-rays to probe the local bonding of Ta atoms within a memristor device. These studies will aid in developing a microscopic switching model, essential for guiding material selection, device engineering, and effective design of driving circuits. Ultimately, any utilization of this technology depends critically on predictive and microphysically accurate device models, and I will describe our work in this area.