Campus Units

Materials Science and Engineering, Ames Laboratory

Document Type


Publication Version

Submitted Manuscript

Publication Date


Journal or Book Title

ACS Applied Materials & Interfaces




Dielectric breakdown of oxides is a main limiting factor for improvement of the performance of electronic devices. Present understanding suggests that defects produced by intense voltage accumulate in the oxide to form a percolation path connecting the two electrodes and trigger the dielectric breakdown. However, reports on directly visualizing the process at nanoscale are very limited. Here, we apply in situ transmission electron microscopy to characterize the structural and compositional changes of amorphous TiO2 under extreme electric field (~100 kV/mm) in a Si/TiO2/W system. Upon applying voltage pulses, the amorphous TiO2 gradually transformed to crystalline sub-stoichiometric rutile TiO2-x and the Magnéli phase Ti3O5. The transitions started from the anode/oxide interface under both field polarities. Preferred growth orientation of rutile TiO2-x with respect to the Si substrate was observed when Si was the anode, while oxidation and melting of the W probe occurred when W was the anode. We associate the TiO2 crystallization process with the electrochemical reduction of TiO2, polarity-dependent oxygen migration, and Joule heating. The experimental results are supported by our phase-field modeling. These findings provide direct details of the defect formation process during dielectric breakdown in amorphous oxides and will help the design of electronic devices with higher efficiency and reliability.


This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acsami.9b08146. Posted with permission.

Copyright Owner

American Chemical Society



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Published Version

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Metallurgy Commons