Size and shape evolution of PS particle layers during etching

Crystalline monolayers of polymer particles are useful templates for surface microstructuring. Here, the authors discuss the use of oxygen plasma to tune interparticle distances in such films. A systematic evaluation of the etch process depending on particle size, plasma power, etching time and particle density was performed. The size evolution of individual particles was analyzed using scanning electron microscopy and compared with different models of the etching process. The authors conclude that none of the existing etch models fit the data very well. Analysis of the particle shape throughout the etching process indicates that changes in particle geometry occur depending on their original size and density. In dense films, bridges form between the particles’ original contact points. Particles increasingly deviate from a spherical geometry. Such shape changes are not captured by current models of the etching process. The authors propose a mechanism to explain the formation of bridges between the particles and their role in the preservation of long-range order. This paper is supplemented by supporting information. The associated files are available online for published issues or can be obtained directly from the managing editor ([email protected]) for Ahead of Print articles.