2, KU Leuven, Leuven, , Belgium
For its capability to remove material while scanning, contact-mode atomic force microscopy has been often used to induce surface modification and small-scale nanofabrication. However, a clear comprehension of the material removal process and its precise control are still missing. Understanding the mechanism of tip-induced wear and formulating a model for its control at the nanoscale, is of great scientific and technological interest as it can enable tomographic sensing using AFM in a slice-and-view methodology. Here, we study the fundamentals of high-pressure tip-induced material removal for various materials using nanosized sliding contacts (made of diamond) in the regime whereby thousands of nm3 are removed. First, we report on the usage of diamond tips to induce the removal of materials with different hardness. Second, the removal is studied as a function of the applied loads with as additional parameter the conditions the AFM scanning conditions. Finally, the impact of the tip-sample interaction inside the worn regions is investigated in order to generate the fundamental understanding on the physical wear mechanisms. We observe a nonlinear variation of the removal rate with the load force which is interpreted as a combination of two contact regimes each dominating in a particular force range. After probing with AFM and SEM the impact of load force and tip scanning conditions, we model the experimental rate of material eroded on each tip passage. A clear challenge is hereby the prediction of the parameters to control the tip-induced removal rate for various materials in order to satisfy a broad range of applications. The gradual transition between the two regimes is used to obtain a controllable removal rate below 5 nm/scan for different materials including semiconductors, metals and oxides.
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