The reliability of piezoelectric thin films is crucial for piezoelectric micro-electromechanical system applications. The understanding of resistance degradation in piezoelectric thin films requires knowledge about point defects. Here, we show the resistance degradation mechanism in the lead-free alternative sodium potassium niobate (KNN) thin films and the relationship to point defects in both field-up and field-down polarities. The conduction mechanism of KNN thin films is found to be Schottky-limited. Furthermore, a reduction in Schottky barrier height accompanies the resistance degradation resulting from interfacial accumulation of additional charged defects. We use thermally stimulated depolarization current measurements and charge-based deep level transient spectroscopy to characterize the defects in KNN thin films. Our results show that oxygen vacancies accumulate at the interface in field-up polarity, and multiple defects accumulate in field-down polarity, potentially oxygen vacancies and holes trapped by potassium vacancies. We use wafer deposition variation to create samples with different film properties. Measurement results from these samples correlate resistance degradation with the defect concentration. We find the natural logarithm of leakage current to be linearly proportional to the defect concentration to the power of 0.25. The demonstrated analysis provides a precise and meaningful process assessment for optimizing KNN thin films.
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17 October 2022
Research Article|
October 18 2022
Resistance degradation in sputtered sodium potassium niobate thin films and its relationship to point defects
Special Collection:
Piezoelectric Thin Films for MEMS
Kuan-Ting Ho
;
Kuan-Ting Ho
a)
(Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing)
1
Engineering Sensor Process Technology, Robert Bosch GmbH
, Reutlingen 72762, Germany
a)Author to whom correspondence should be addressed: KuanTing.Ho@de.bosch.com
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Daniel Monteiro Diniz Reis;
Daniel Monteiro Diniz Reis
(Conceptualization, Data curation, Project administration, Resources, Software, Supervision, Writing – review & editing)
1
Engineering Sensor Process Technology, Robert Bosch GmbH
, Reutlingen 72762, Germany
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Karla Hiller
Karla Hiller
(Supervision, Writing – review & editing)
2
Center for Microtechnologies, Technical University Chemnitz
, Chemnitz 09126, Germany
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a)Author to whom correspondence should be addressed: KuanTing.Ho@de.bosch.com
Note: This paper is part of the APL Special Collection on Piezoelectric Thin Films for MEMS.
Appl. Phys. Lett. 121, 162902 (2022)
Article history
Received:
June 28 2022
Accepted:
September 24 2022
Citation
Kuan-Ting Ho, Daniel Monteiro Diniz Reis, Karla Hiller; Resistance degradation in sputtered sodium potassium niobate thin films and its relationship to point defects. Appl. Phys. Lett. 17 October 2022; 121 (16): 162902. https://doi.org/10.1063/5.0106382
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