dc.description.popularabstract | In this thesis, we have explored two ambits of current interest in AFM. First, that of force reconstruction under ambient conditions. Second, that of image generation in multifrequency AFM. Arguably, the tip-surface force profile contains all the phenomena to be explained in AFM. In particular, the force profile can, and has typically been, explained by models where the motivation typically is 1) to show that a given model, derived or known, matches the experimental force profile to then 2) extract material properties from it by either providing as much accuracy as possible, increasing throughput, or both.
The first part of this thesis has been dedicated to inspecting the force profile as such without necessarily concerning ourselves with throughput. Our approach has shown that:
1) the “attractive” part of the force profile, typically explained as the short-range van der Waals force, does not necessarily follow an inverse square law (2015). In fact, we have shown that power laws of 3-20 might be more suitable to describe the tip-surface interaction. This is particularly the case for the sharpest tips, i.e. R<20-30 nm. Above this range the power law can be said to be 2 as expected. This point puts restrictions to high resolution imaging since the shape of the force becomes tip size dependent. We could argue that it might be possible to modify the force expression to make it independent of the tip size by we have not shown it in our work.
2) That the procedure of recovering the force profile does not necessarily meet the conditions required by the central limit theorem which in turn allows assuming a normal distribution (2015). The main consequence of this second point is that acquiring ~30 data points per pixel does not justify providing a mean and a standard deviation of a given parameter in order to account for errors. That is, the true mean is not correctly explained in this way implying that reproducibility is at stake.
3) This first part of the thesis finishes with a machine learning approach to parametrizing the force (2016, 2019). With this approach the underlying phenomena can manifest via any complexity, i.e. power law, or any possible distance dependent function, without restricting accuracy, overfitting or bias. A disadvantage of this method is the increase of complexity in the computational side. In the thesis, this part is actually presented last.
The second part of the thesis is dedicated to recover the parameter that is typically used to explain the van der Waals force interaction in ambient AFM, i.e. the Hamaker or H, while imaging. We assumed a power law of 2 (2015) and analytically derived an expression to recover H by exploiting the multifrequency method. Here two expressions are experimentally available and describe the attractive part of the force in terms of two unknowns, i.e. the minimum tip-surface distance and H. We have shown that an analytical solution is available assuming certain standard experimental conditions. This approach allows for higher throughput and quasi-instantaneous recovery of the parameter while performing standard multifrequency imaging. | en_US |
dc.relation.haspart | <p>Paper 1: Lai, C.Y., Santos, S. & Chiesa, M. (2019). Machine Learning Assisted Quantification of Graphitic Surfaces Exposure to Defined Environments. <i>Applied Physics Letters, 114</i>, 241601. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1063/1.5095704>https://doi.org/10.1063/1.5095704</a>.
<p>Paper 2: Sloyan, K., Lai, C.Y., Lu, J.Y., Alfakes, B., Al Hassan, S., Almansouri, I., Dahlem, M.S. & Chiesa, M. (2018). Discerning the Contribution of Morphology and Chemistry in Wettability Studies. <i>Journal of Physical Chemistry A, 122</i>(38), 7768-7773. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href= https://doi.org/10.1021/acs.jpca.8b04197> https://doi.org/10.1021/acs.jpca.8b04197</a>. Accepted manuscript version available in Munin at <a href=https://hdl.handle.net/10037/14572>https://hdl.handle.net/10037/14572</a>.
<p>Paper 3: Santos, S., Lai, C.Y., Amadei, C.A., Gadelrab, K.R., Tang, T.C., Verdaguer, A., Barcons, V., Font, J., Colchero, J. & Chiesa, M. (2016). The Mendeleev-Meyer force project. <i>Nanoscale, 8</i>(40), 17400-17406. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1039/C6NR06094C>https://doi.org/10.1039/C6NR06094C</a>.
<p>Paper 4: Lai, C.Y., Perri, S., Santos, S., Garcia, R. & Chiesa, R. (2016). Rapid quantitative chemical mapping of surfaces with sub-2nm resolution. <i>Nanoscale, 8</i>(16), 9688-9694. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1039/C6NR00496B>https://doi.org/10.1039/C6NR00496B</a>.
<p>Paper 5: Lai, C.Y., Santos, S. & Chiesa, M. (2016). Systematic Multidimensional Quantification of Nanoscale Systems From Bimodal Atomic Force Microscopy Data. <i>ACS Nano, 10</i>(6), 6265-6272. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1021/acsnano.6b02455>https://doi.org/10.1021/acsnano.6b02455</a>.
<p>Paper 6: Lai, C.Y., Santos, S. & Chiesa, M. (2016). Reconstruction of height of sub-nm steps with bimodal atomic force microscopy. <i>Nanotechnology, 27</i>(7), 075701. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=http://dx.doi.org/10.1088/0957-4484/27/7/075701>http://dx.doi.org/10.1088/0957-4484/27/7/075701</a>.
<p>Paper 7: Lai, C.Y., Olukan, T., Santos, S., Al Ghaferi, A. & Chiesa, M. (2015). The power laws of nanoscale forces in ambient conditions. <i>Chemical Communications, 51</i>(99), 17619-17622. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1039/C5CC05755H>https://doi.org/10.1039/C5CC05755H</a>.
<p>Paper 8: Lai, C.Y., Cozzolino, M., Diamanti, M.V., Al Hassan, S. & Chiesa, M. (2015). Underling mechanism of time dependent surface properties of calcite (CaCO<sub>3</sub>): a baseline for investigations of reservoirs wettability. <i>Journal of Physical Chemistry C, 119</i>(52), 29038-29043. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=http://dx.doi.org/10.1021/acs.jpcc.5b10595> http://dx.doi.org/10.1021/acs.jpcc.5b10595</a>.
<p>Paper 9: Chiesa, M. & Lai, C.Y. (2018). Surface aging investigation by means of an AFM-based methodology and the evolution of conservative nanoscale interactions. <i>Physical Chemistry Chemical Physics, 20</i>(29), 19664-19671. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1039/C8CP03454K> https://doi.org/10.1039/C8CP03454K</a>. Accepted manuscript version available in Munin at <a href=https://hdl.handle.net/10037/15092>https://hdl.handle.net/10037/15092</a>.
<p>Paper 10: Santos, S., Lai, C.Y., Olukan, T. & Chiesa, M. (2017). Multifrequency AFM: from origins to convergence. <i>Nanoscale, 9</i>(16), 5038-5043. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1039/C7NR00993C>https://doi.org/10.1039/C7NR00993C</a>.
<p>Paper 11: Garlisi, C., Scandura, G., Palmisano, G., Chiesa, M. & Lai, C.Y. (2016). Integrated Nano-and Macroscale Investigation of Photoinduced Hydrophilicity in TiO<sub>2</sub> Thin Films. <i>Langmuir, 32</i>(45), 11813-11818. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1021/acs.langmuir.6b03756>https://doi.org/10.1021/acs.langmuir.6b03756</a>.
<p>Paper 12: Chang, Y.H., Olukan, T., Lai, C.Y., Santos, S., Lin, T.Y., Apostoleris, H., … Chiesa, M. (2015). Establishing nanoscale heterogeneity with nanoscale force measurements. <i>Journal of Physical Chemistry C, 119</i>(32), 18267-18277. Published version not available in Munin due to publisher’s restrictions. Published version available at <a href=https://doi.org/10.1021/acs.jpcc.5b04456>https://doi.org/10.1021/acs.jpcc.5b04456</a>. | en_US |