The deposition of thin films of reactive metals can damage or even melt the underlying substrate. One solution to this problem is to use a rare-gas "buffer layer" that can absorb and dissipate energy, and thereby allow a cooled film to "soft land" on the surface. Kerner and Asscher combine soft landing with laser-induced thermal desorption to create potassium nanowires that are less than 30 nm wide and 5 mm in length on a ruthenium substrate. Laser gratings are used to desorb regions of unwanted potassium and its xenon buffer layer. A slower thermal annealing step removes the remaining xenon buffer, and the potassium wires absorb gently onto the substrate. In a commentary, Weaver and Antonov argue that the buffer-layer approach should prove to be a general way of patterning "almost anything on anything." -- PDS
Surf. Sci. 557, 5;1 (2004).