How can trapped charges influence local electrical behavior in stacked nanocapacitor layers?
Leifang Zhang, Christophe Gatel, and their colleagues at CEMES-CNRS, Helmholtz-Zentrum Berlin, Freie Universität Berlin, and Université Paul Sabatier published on their use of the Hummingbird Scientific in-situ biasing TEM holder to quantify the charges trapped at dielectric/dielectric interfaces as well as metal/dielectric interfaces in HfO2– and Al2O3-based nanocapacitors using operando off-axis electron holography. Focused-ion beam lamellae extracted from two stacks, HfO2/Al2O3/HfO2 and Al2O3/HfO2/Al2O3 were characterized for charge trapping/detrapping and simulated using finite element modeling (FEM).
a,f) FIB lamellae schematic and TEM image of stack A: HfO2/Al2O3/HfO2 and stack B: Al2O3/HfO2/Al2O3. b,g) Sketches of stacks A and B. c,h) TEM images layers of the nanocapacitors A and B. d,i) Phase maps of projected electric potential on the same area obtained by electron holography for the nanocapacitors A and B with an applied bias of +6 V. e,j) Phase maps for the nanocapacitors A and B with an applied bias of -6 V. Scale bars are 20 nm in (c) and (h). Copyright © 2024 The Author(s). Advanced Materials published by Wiley-VCH GmbH
The lamellae were affixed bridging the leads of the biasing microchips. The electrostatic potentials were mapped at sub-nanometer spatial resolution with a bias applied. Negative and positive trapped charges at different interfaces were identified and then linked to their overall contribution to the electric field distribution. The bias dependence of the interfacial charges is similar for the HfO2/Al2O3 and Al2O3/HfO2 interfaces, but the sign of the charge trapped is opposite as expected: negative for Al2O3/HfO2 and positive for HfO2/Al2O3. The Hummingbird Scientific biasing holder was used to apply the highly sensitive electron holography technique to reveal, for the first time, a linear relationship between the interfacial trapped charges and the applied bias, and the effect of the trapped charges on the local electrical behavior.
Reference: Leifeng Zhang, Muhammad Hamid Raza, Rong Wu, Kilian Gruel, Catherine Dubourdieu, Martin Hÿtch, Christophe Gatel, Advanced Materials 37 (4) (2024) DOI: 10.1002/adma.202413691
Full paper Copyright © 2024 The Author(s). Advanced Materials published by Wiley-VCH GmbH
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