In situ TEM Study of the Amorphous-to-Crystalline Transition during

Dielectric Breakdown in TiO2 Film

Xinchun Tian1, Chloe Cook2, Wei Hong3, Tao Ma4, Geoff L. Brennecka2, and Xiaoli Tan1,*

1 Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011, USA

2 Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO

80401, USA

3 Department of Mechanics and Aerospace Engineering, Southern University of Science and

Technology, Shenzhen, Guangdong 518055, China

4 Ames Laboratory, US Department of Energy, Ames, IA 50011, USA

Abstract: 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,

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In situ TEM Study of the Amorphous-to-Crystalline Transition duringDielectric Breakdown in TiO2 FilmXinchun Tian1, Chloe Cook2, Wei Hong3, Tao Ma4, Geoff L. Brennecka2, and Xiaoli Tan1,*1 Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011, USA2 Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO80401, USA3 Department of Mechanics and Aerospace Engineering, Southern University of Science andTechnology, Shenzhen, Guangdong 518055, China4 Ames Laboratory, US Department of Energy, Ames, IA 50011, USAAbstract: Dielectric breakdown of oxides is a main limiting factor for improvement of theperformance of electronic devices. Present understanding suggests that defects produced byintense voltage accumulate in the oxide to form a percolation path connecting the two electrodesand trigger the dielectric breakdown. However, reports on directly visualizing the process atnanoscale are very limited. Here, we apply in situ transmission electron microscopy tocharacterize the structural and compositional changes of amorphous TiO2 under extreme electricfield (~100 kV/mm) in a Si/TiO2/W system. Upon applying voltage pulses, the amorphous TiO2gradually transformed to crystalline sub-stoichiometric rutile TiO2-x and the Magnéli phaseTi3O5. 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 whenSi 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,Page 1 of 26ACS Paragon Plus EnvironmentACS Applied Materials & InterfacesACS Applied

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