Nanoscale density variations in sputtered amorphous TaOx functional layers in resistive switching devices

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....

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Bibliographic Details
Published in:Journal of applied physics 2020-02, Vol.127 (5)
Main Authors: Xu, Qiyun, Ma, Yuanzhi, Skowronski, Marek
Format: Article
Language:English
Subjects:
Applied physics
Cellular structure
Density ratio
Memory devices
Random access memory
Scanning transmission electron microscopy
Substrates
Surface roughness
Surface roughness effects
Thin films
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Summary: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.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5134098