%AXu, Qiyun%AXu, Qiyun [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA]%AMa, Yuanzhi%AMa, Yuanzhi [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA]%ASkowronski, Marek%ASkowronski, Marek [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA]%BJournal Name: Journal of Applied Physics; Journal Volume: 127; Journal Issue: 5; Related Information: CHORUS Timestamp: 2023-07-15 21:17:01 %D2020%IAmerican Institute of Physics %JJournal Name: Journal of Applied Physics; Journal Volume: 127; Journal Issue: 5; Related Information: CHORUS Timestamp: 2023-07-15 21:17:01 %K %MOSTI ID: 10133180 %PMedium: X %TNanoscale density variations in sputtered amorphous TaOx functional layers in resistive switching devices %X

The density variations in reactively sputtered amorphous TaOx thin films deposited on planar and patterned substrates have been quantified by high-angle annular dark-field scanning transmission electron microscopy. The experiments have been performed both in plan-view and cross-sectional geometries. The planar films exhibit a cellular structure consisting of high-density cells with low-density boundaries. Laterally, cell sizes varied from 5 to 20 nm as the deposition temperature was changed from 298 K to 573 K. The corresponding density ratio of the cell boundary over the cell interior varied between 0.98 and 0.93 corresponding to 2%–7% free volume in the functional layer. The film microstructure is consistent with the self-shadowing effect of surface roughness. Similar low-density areas were found at the locations of steps of the patterned substrates with a local density decrease of up to 9%. The influence of the low-density region in the resistive random-access memory device is discussed.

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