| Summary: | 碩士 === 明志科技大學 === 材料工程系碩士班 === 106 === A series of yttria-stabilized-zirconia (YSZ)-based resistive random access memory (RRAM) with characteristically different YSZ microstructures are investigated. The RRAM consists of a Mo bottom electrode (300 nm), a YSZ dielectric film (30 nm) and an Al top electrode (300 nm). The microstructure is controlled by changing the target poisoning rate and the annealing temperature.
The YSZ film is mainly produced by the optical emission spectroscopy (OES) detected by the plasma emission monitor (PEM) loop control, the ZrY alloy target is changed under the poisoning rate and the YSZ film of the different structure is deposited. The crystal structure of the film was analyzed by X-ray diffraction, and the microstructure of the film was confirmed by a transmission electron microscope (TEM).
The transition-mode reactive sputtering corresponding to 20% of target poisoning is employed to produce the YSZ film with a microstructure having ultrafine crystallites embedded in an amorphous matrix, while a poisoned-mode reactive sputtering corresponding to 95% of target poisoning is equiaxed grains.
Such a YSZ film undergoes an abnormal grain growth upon annealing at 400°C for 2 hours. The grain boundary of this coarse-grained YSZ film is found to be aligned perpendicular to the electrode-YSZ interface. This can be rationalized by yttrium segregation, thus oxygen vacancy segregation, along with grain boundaries in which a higher concentration of oxygen vacancy is expected in the former. So is a more easily formed filament.
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