Dewetting

<h2 id="dewetting-of-polymer-thin-films">Dewetting of polymer thin films</h2>
<p>In most dewetting studies a thin <a href="/facts/Polymer/eF32E50K">polymer</a> film is <a href="/facts/Spin_coating/IsgQN2nK">spin-cast</a> onto a substrate. Even in the case of 
  
    
      
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 the film does not dewet immediately if it is in a metastable state, e.g. if the temperature is below the <a href="/facts/Glass_transition_temperature/yVl3QzsT">glass transition temperature</a> of the polymer. Annealing such a metastable film above its glass transition temperature increases the mobility of the polymer-chain molecules and dewetting takes place.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
</p><p>The process of dewetting occurs by the nucleation and growth of randomly formed holes, which coalesce to form a network of filaments, before breaking into droplets.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>  When starting from a continuous film, an irregular pattern of droplets is formed. The droplet size and droplet spacing may vary over several orders of magnitude, since the dewetting starts from randomly formed holes in the film. There is no spatial correlation between the dry patches that develop. These dry patches grow and the material is accumulated in the rim surrounding the growing hole. In the case where the initially homogeneous film is thin (in the range of 100 nm), a <a href="/facts/Polygon/yAq7RjPz">polygon</a> network of connected strings of material is formed, like a <a href="/facts/Voronoi_pattern/AhQY5LD8">Voronoi pattern</a> of polygons. These strings then can break up into droplets, a process which is known as the <a href="/facts/Plateau-Rayleigh_instability/DpDfW3Pm">Plateau-Rayleigh instability</a>. At other film thicknesses, other complicated patterns of droplets on the substrate can be observed, which stem from a fingering instability of the growing rim around the dry patch.
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<h2 id="dewetting-of-metal-thin-films">Dewetting of metal thin films</h2>
<p>Solid-state dewetting of the metal thin films describe the transformation of a thin film into an energetically favoured set of droplets or particles at temperatures well below the melting point. The driving force for dewetting is the minimization of the total energy of the free surfaces of the film and substrate as well as of the film-substrate interface.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> The dedicated heating stage in SEM has been widely used to accurately control sample temperature  through a thermocouple to observe the in-situ behaviour of the material, and can be recorded as a video format.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Meanwhile, the two-dimensional morphology can be directly observed and characterised. ie. the partially dewetted Ni film is itself a workable fuel electrode for SOCs as it provides long TPB lines if the structure is fine enough, the connectivity of the nickel and pore phases as well as the TPB lines can be used for SOFC characterisation.
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<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to Dewetting.

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Leroy, F.; Borowik, Ł.; Cheynis, F.; Almadori, Y.; Curiotto, S.; Trautmann, M.; Barbé, J.C.; Müller, P. (2016). "How to control solid state dewetting : A short review". Surface Science Reports. 71 (2): 391. Bibcode:2016SurSR..71..391L. doi:10.1016/j.surfrep.2016.03.002. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Rosen, Milton J. (2004). Surfactants and Interfacial Phenomena (3rd ed.). Hoboken, New Jersey: Wiley-Interscience. p. 244. ISBN 978-0-471-47818-8. OCLC 475305499. <a href="978-0-471-47818-8" target="_blank">978-0-471-47818-8</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Carroll, Gregory T.; Turro, Nicholas J.; Koberstein, Jeffrey T. (2010) Patterning Dewetting in Thin Polymer Films by Spatially Directed Photocrosslinking Journal of Colloid and Interface Science, Vol. 351, pp 556-560 doi:10.1016/j.jcis.2010.07.070 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Leroux, Frédéric; Campagne, Christine; Perwuelz, Anne; Gengembre, Léon (2008). "Polypropylene film chemical and physical modifications by dielectric barrier discharge plasma treatment at atmospheric pressure". Journal of Colloid and Interface Science. 328 (2): 412–20. Bibcode:2008JCIS..328..412L. doi:10.1016/j.jcis.2008.09.062. PMID 18930244. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Karapanagiotis, Ioannis; Gerberich, William W. (2005). "Polymer film rupturing in comparison with leveling and dewetting". Surface Science. 594 (1–3): 192–202. Bibcode:2005SurSc.594..192K. doi:10.1016/j.susc.2005.07.023. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Reiter, Günter (1992-01-06). "Dewetting of thin polymer films". Physical Review Letters. 68 (1): 75–78. Bibcode:1992PhRvL..68...75R. doi:10.1103/PhysRevLett.68.75. PMID 10045116. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Song, Bowen; Bertei, Antonio; Wang, Xin; Cooper, Samuel J.; Ruiz-Trejo, Enrique; Chowdhury, Ridwanur; Podor, Renaud; Brandon, Nigel P. (April 2019). "Unveiling the mechanisms of solid-state dewetting in Solid Oxide Cells with novel 2D electrodes". Journal of Power Sources. 420: 124–133. Bibcode:2019JPS...420..124S. doi:10.1016/j.jpowsour.2019.02.068. hdl:11568/964958. S2CID 108162800. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>Song, Bowen; Bertei, Antonio; Wang, Xin; Cooper, Samuel J.; Ruiz-Trejo, Enrique; Chowdhury, Ridwanur; Podor, Renaud; Brandon, Nigel P. (2019). "In-situ Ni Solid State Dewetting Videos". 420. doi:10.5281/zenodo.2546395. {{cite journal}}: Cite journal requires |journal= (help) <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
</ol>

Dewetting open-in-new

Dewetting