This dissertation introduces the design, fabrication, and application of acopper-oxide-based memristor for the passive sensing of oxygen and other gases.The device design was as follows: Deposition of copper (Cu) bottom electrodes,(oxygen) vacancy-rich copper oxide (CuxO) switching layers, and tungsten (W) topelectrodes in a crossbar array structure. The CuxO layer was deposited via reactivesputtering of a Cu target with an argon-oxygen (Ar/O2) mixture. A portion of thislayer was extended from each array cell to be exposed for sensing. Memristivedevices of different switching layer thicknesses were initially explored forirreversible sensing of oxygen in ambient air. Results of this first experimentdemonstrated an increase in resistance states upon prolonged exposure toambient air. For the second experiment, memristive devices were fabricated withsub-micron holes that were etched into the W top electrode to better reveal theswitching layer surface. The devices were also subjected to ambient oxygen at 180deg C to induce passive sensing in minutes. Resistance results were consistentwith the first experiment but also revealed a dependence on the surface area ofthe exposed oxide. Finally, memristive devices were investigated in a thirdexperiment for reversible sensing of an oxidizing gas and reducing gas at roomtemperature. This time, changes were not only observed in resistance but also inhysteresis (current versus voltage) depending on the type of gas introduced.Overall, this work demonstrates a step towards the use of the memristor as a gassensor, which we have named “memsensors”, by taking advantage of the device’sability to memorize (or record) historical information.
Read
