The Hodgkin-Huxley model for action potential generation in biological axons is central for understanding the computational capability of the nervous system and emulating its functionality. Owing to the historical success of silicon complementary metal-oxide-semiconductors, spike-based computing is primarily confined to software simulations and specialized analogue metal-oxide-semiconductor field-effect transistor circuits. However, there is interest in constructing physical systems that emulate biological functionality more directly, with the goal of improving efficiency and scale. The neuristor was proposed as an electronic device with properties similar to the Hodgkin-Huxley axon, but previous implementations were not scalable. Here we demonstrate a neuristor built using two nanoscale Mott memristors, dynamical devices that exhibit transient memory and negative differential resistance arising from an insulating-to-conducting phase transition driven by Joule heating. This neuristor exhibits the important neural functions of all-or-nothing spiking with signal gain and diverse periodic spiking, using materials and structures that are amenable to extremely high-density integration with or without silicon transistors.

We report sub-nanosecond switching of a metal-oxide-metal memristor utilizing a broadband 20 GHz experimental setup developed to observe fast switching dynamics. Set and reset operations were successfully performed in the tantalum oxide memristor using pulses with durations of 105 and 120 ps, respectively. Reproducibility of the sub-nanosecond switching was also confirmed as the device switched over consecutive cycles.

Chemical vapor deposition of germanium onto the silicon (001) surface at atmospheric pressure and 600 degrees Celsius has previously been shown to produce distinct families of smaller (up to 6 nanometers high) and larger (all approximately 15 nanometers high) nanocrystals. Under ultrahigh-vacuum conditions, physical vapor deposition at approximately the same substrate temperature and growth rate produced a similar bimodal size distribution. In situ scanning tunneling microscopy revealed that the smaller square-based pyramids transform abruptly during growth to significantly larger multifaceted domes, and that few structures with intermediate size and shape remain. Both nanocrystal shapes have size-dependent energy minima that result from the interplay between strain relaxation at the facets and stress concentration at the edges. A thermodynamic model similar to a phase transition accounts for this abrupt morphology change.

We demonstrate over 1×1010 open-loop switching cycles from a simple memristive device stack of Pt/TaOx/Ta. We compare this system to a similar device stack based on titanium oxides to obtain insight into the solid-state thermodynamic and kinetic factors that influence endurance in metal-oxide memristors.

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The initial stages of GaAs overgrowth over self-assembled coherently strained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially covered island structures with a regular size distribution which are elongated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking place during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are consistent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity indicating that surface QDs are remarkably insensitive to surface recombination effects.

Hybrid reconfigurable logic circuits were fabricated by integrating memristor-based crossbars onto a foundry-built CMOS (complementary metal-oxide-semiconductor) platform using nanoimprint lithography, as well as materials and processes that were compatible with the CMOS. Titanium dioxide thin-film memristors served as the configuration bits and switches in a data routing network and were connected to gate-level CMOS components that acted as logic elements, in a manner similar to a field programmable gate array. We analyzed the chips using a purpose-built testing system, and demonstrated the ability to configure individual devices, use them to wire up various logic gates and a flip-flop, and then reconfigure devices.

Titanium dioxide memristive devices have been non‐destructively characterized using x‐ray absorption spectromicroscopy and TEM. These techniques allow direct identification of the chemistry and structure of the conducting channel responsible for the bipolar resistance switching seen in these devices. Within the TiO2 matrix, we observe the formation of a Ti4O7 Magnéli phase possessing metallic properties and ordered planes of oxygen vacancies.