Controlled rupturing of thin films can make low-cost nanopatterned arrays for solar cells and biomolecular detection

Solid state films freshly applied to microelectronic

devices sometimes split apart at temperatures much lower than typical melting points, due to the high energy at the interface between the film and substrate. This dewetting effect is increasingly problematic at nanoscale film dimensions; however it has also inspired researchers looking for an easy way to produce patterned substrates.
Liangxing Lu from the A*STAR Institute of High Performance Computing and co-workers recently demonstrated that metal films can be transformed into 'nano-aperture' arrays—tiny pores with dimensions controllable down to 10 nanometers—by performing dewetting on surface templates containing 3-D ridges and ripples. However, the team found that the templates only produced nano-apertures from metal films of a certain thickness; otherwise, random nanodot features appeared.
"Many factors influence the dewetting process, and also there are many types of equilibrium structures," says Lu. "Finding the conditions for select morphologies is complex and difficult."
To use dewetting for other nanostructure shapes, Lu and colleagues developed a custom algorithm to simulate  dewetting. Their technique calculates all possible nanopatterns for a dewetting film on a template and spots the lowest energy configuration. Then, diffusion calculations expose how movements between adjacent nano-islands lower the system's total free energy.
"This model ignores the detailed kinetics, and instead analyzes the diffusion paths of equilibrium morphologies on a given substrate," explains Lu. "The only driving forces are the surface and interface energies, which simplifies the problem."
Through their calculations, the researchers produced detailed descriptions of droplet coalescence inside pit-shaped templates, and beading on top of table-like 'mesa' templates. Then, they generated phase diagrams that identified possible dewetting behavior on differently shaped templates—guidelines that proved useful for fabrication trials.


Read more at: https://phys.org/news/2017-06-rupturing-thin-low-cost-nanopatterned-arrays.html#jCp