Improving the Reliability of Conductive Atomic Force Microscopy
[eng] Owing to its exceptional topographical resolution and electrical sensitivity, Conductive Atomic Force Microscopy (C AFM) has become an essential tool for nanoscale material analysis. However, achieving reproducible data in C AFM remains a challenge, primar ily due to the multitude of factors i...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/211125 |
| Acceso en línea: | https://hdl.handle.net/2445/211125 http://hdl.handle.net/10803/690847 |
| Access Level: | acceso abierto |
| Palabra clave: | Microscòpia de força atòmica Atomic force microscopy |
| Sumario: | [eng] Owing to its exceptional topographical resolution and electrical sensitivity, Conductive Atomic Force Microscopy (C AFM) has become an essential tool for nanoscale material analysis. However, achieving reproducible data in C AFM remains a challenge, primar ily due to the multitude of factors influencing the stability of the tip sample contact. Among these, tip degradation stands out as a particularly critical issue. To attain high topographical resolution, C AFM probes are designed with small tip radii, but this makes them more susceptible to degradation. Such degradation primarily manifests in two forms. Firstly, since C AFM measurements are commonly performed in contact mode, mechanical abrasion due to lateral frictions. Secondly, exposure to high current d ensities, an inherent consequence of the small tip radii, can lead to partial or complete melting of the probe's conductive coating. While the issue of mechanical abrasion has been mitigated to some extent by performing C AFM measurements in intermittent c ontact mode a recent advancement in the field this thesis concentrates on developing strategies to minimize tip degradation caused by high current densities. To ascertain the current status quo, an in depth analysis of the degradation dynamics of Pt /Ir coated Si probes, currently predominant in C AFM applications, is conducted. In the course of this research, solid Pt probes are examined as a promising alternative. While they exhibit a slightly lower topographical resolution compared to Pt/Ir coated pro bes, their superior endurance through numerous scans and enhanced electrical durability are significant advantages. Beyond utilizing more durable probes, another approach discussed in this thesis is the active limitation of resulting currents, such as thro ugh software based current limitation. This technique allows for extended use of metal coated probes (by approximately a factor of 50, as detailed in Chapter 4.2.1), while also protecting the sample from current induced damage. However, it is noted that so ftware based current limitation does not achieve absolute current limitation. A major contribution of this thesis is the introduction of a novel current limiting sample holder that achieves true current limitation. Unlike software based methods, this holde r restricts currents in both sweep directions through the integration of a MOSFET. This thesis not only deepens our understanding of probe performance in C AFM but also enhances the reliability and cost effectiveness of C AFM studies. Additionally, it open s new avenues for application by providing the ability to precisely control currents during measurements. This is particularly beneficial for analyzing sensitive samples, a need that is becoming increasingly critical with the trend towards smaller device dimensions in recent technology developments. |
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