Physical origins of current and temperature controlled negative differential resistances in NbO.

Negative differential resistance behavior in oxide memristors, especially those using NbO, is gaining renewed interest because of its potential utility in neuromorphic computing. However, there has been a decade-long controversy over whether the negative differential resistance is caused by a relatively low-temperature non-linear transport mechanism or a high-temperature Mott transition. Resolving this issue will enable consistent and robust predictive modeling of this phenomenon for different applications.

Conduction Channel Formation and Dissolution Due to Oxygen Thermophoresis/Diffusion in Hafnium Oxide Memristors.

Transition-metal-oxide memristors, or resistive random-access memory (RRAM) switches, are under intense development for storage-class memory because of their favorable operating power, endurance, speed, and density. Their commercial deployment critically depends on predictive compact models based on understanding nanoscale physicochemical forces, which remains elusive and controversial owing to the difficulties in directly observing atomic motions during resistive switching, Here, using scanning transmission synchrotron X-ray spectromicroscopy to study in situ switching of hafnium oxide memristors, we directly observed the formation of a localized oxygen-deficiency-derived conductive channel surrounded by a low-conductivity ring of excess oxygen. Subsequent thermal annealing homogenized the segregated oxygen, resetting the cells toward their as-grown resistance state.

Electrowetting-induced dewetting transitions on superhydrophobic surfaces.

We develop and demonstrate the use of electrowetting to achieve the dewetting (Wenzel-to-Cassie transition) of superhydrophobic surfaces. We effect this transition by means of an opposing flat plate and a three-electrode system; the liquid droplet is completely pulled out of its wetted Wenzel state upon the application of a suitable voltage. We also experimentally quantify the dissipative forces preventing the dewetting transition.