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Materials 2019, 12(3), 459; https://doi.org/10.3390/ma12030459

Understanding Current Instabilities in Conductive Atomic Force Microscopy

1
Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nanoscience & Technology, Soochow University, Suzhou 215123, China
2
Department of Electrical Engineering, Media Technology and Computer Science, Deggendorf Institute of Technology, 94469 Deggendorf, Germany
3
Dipartimento di Ingegneria “Enzo Ferrari”, Università degli Studi di Modena e Reggio Emilia, 41125 Modena (MO), Italy
4
Dipartimento di Scienze e Metodi dell’ Ingegneria, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (RE), Italy
5
Department of Mechanical Engineering and Mechatronics, Deggendorf Institute of Technology, 94469 Deggendorf, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work
Received: 21 December 2018 / Revised: 24 January 2019 / Accepted: 27 January 2019 / Published: 1 February 2019
(This article belongs to the Section Structure Analysis and Characterization)
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PDF [2475 KB, uploaded 2 February 2019]
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Abstract

: Conductive atomic force microscopy (CAFM) is one of the most powerful techniques in studying the electrical properties of various materials at the nanoscale. However, understanding current fluctuations within one study (due to degradation of the probe tips) and from one study to another (due to the use of probe tips with different characteristics), are still two major problems that may drive CAFM researchers to extract wrong conclusions. In this manuscript, these two issues are statistically analyzed by collecting experimental CAFM data and processing them using two different computational models. Our study indicates that: (i) before their complete degradation, CAFM tips show a stable state with degraded conductance, which is difficult to detect and it requires CAFM tip conductivity characterization before and after the CAFM experiments; and (ii) CAFM tips with low spring constants may unavoidably lead to the presence of a ~1.2 nm thick water film at the tip/sample junction, even if the maximum contact force allowed by the setup is applied. These two phenomena can easily drive CAFM users to overestimate the properties of the samples under test (e.g., oxide thickness). Our study can help researchers to better understand the current shifts that were observed during their CAFM experiments, as well as which probe tip to use and how it degrades. Ultimately, this work may contribute to enhancing the reliability of CAFM investigations. View Full-Text
Keywords: CAFM; tip degradation; tunneling current; water meniscus; modeling CAFM; tip degradation; tunneling current; water meniscus; modeling
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Jiang, L.; Weber, J.; Puglisi, F.M.; Pavan, P.; Larcher, L.; Frammelsberger, W.; Benstetter, G.; Lanza, M. Understanding Current Instabilities in Conductive Atomic Force Microscopy. Materials 2019, 12, 459.

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