First, the team patterned the surface of indium phosphide by coating it selectively with a gold layer only a few nanometers thick. Upon heating, the film breaks up into droplets and the underlying InP dissolves into the gold nanoparticles.
Water vapour is then introduced into the system. At temperatures of less than 300°C, the gold alloy etches nanoscale pits into the InP. However, at 440°C and higher, the process formed long V-shaped nanochannels which followed straight paths dictated by the crystalline lattice. The dimensions of the grooves correspond to the size of droplet, which can be controlled.
The work started as a potential way of creating nanowires. “We were disappointed, at first,” said NIST researcher Babak Nikoobakht. “Then we figured out that water was the contaminant in the process – a problem that turned out to be a good thing.”
The team has seen the same results when working with gallium phosphide and indium arsenide and Nikoobakht believes that, with adjustments, the etching process might also work for creating patterns of channels on silicon and other materials.
