Lab talk
Jan 3, 2008
Real-time observation of FIB-created dots and ripples on GaAs
The Focused Ion Beam (FIB) is not only a post-processing tool for microelectronics fabrication but also an instrument used to synthesize and self-assemble new nanomaterials and nanostructures. For instance, it is possible to use the Ga+ beam of the FIB to create self-assembled dots and pseudo-periodically aligned ripples on metallic and semiconducting surfaces. The FIB nanofabrication of dots and ripples can be described as the result of a dynamic competition between roughening and smoothing processes that depend on the nature and the morphology of the surface.
In the work carried out at LIMMS (Laboratory for Integrated Micro-Mechatronic Systems) by Dr F Rose, in collaboration with Prof H Kawakatsu and Prof H Fujita, an in situ monitoring of Ga dot and ripple formation by FIB sputtering on GaAs(001) is reported. It shows for the first time FIB movies that allow the formation and diffusion of dots and ripples in real time to be studied.
The results strongly suggest that under continuous sputtering, dots diffuse and self-assemble to form ripples. With increasing ion dose the evolution of the surface morphology of sputtered GaAs(001) can be classified in three regimes. At low dose, Ga dots (50–460 nm) are formed and diffuse on the surface under continuous FIB irradiation. At intermediate dose, Bradley-Harper type ripples appear (1150 ± 25 nm pseudo-period). At higher doses, additional sputtering flattens the ripples which are eroded into microplanes.
About the author
Dr F Rose was a JSPS Fellow at LIMMS, a French-Japanese laboratory operated jointly by the CNRS (Centre National de la Recherche Scientifique) and the IIS (Institute of Industrial Science) at the University of Tokyo in Japan. He is currently a postdoc with Prof M Salmeron at the Lawrence Berkeley National Laboratory in California. Prof H Kawakatsu and Prof H Fujita are leading respective laboratories in the fields of scanning probes and micro and nano electro mechanical systems at the IIS.
