In-situ X-Ray Diffraction of GaSb while Normal Incidence Sputtering

Because of today’s micro- and optoelectronics need for functional structures in submicron range the research in creating those structures gained much interest during the past years. In order to produce such nanometer sized devices there are two complementary approaches: the “top-down” and the “bottom-up” approach. The first case is represented by conventional processes like lithography, whereas the latter one makes use of self-organization phenomena. It has been shown that low energy (typically 0.1 – 10 keV) ion sputtering induces such a self-organized process at the irradiated surface which leads to the formation of periodic structures of size ranging from 10 to 100 nm [1]. This way periodic ripple patterns can be achieved for oblique ion beam incidence and hexagonally ordered dot arrays for normal incidence. The evolution of ripple structures on different semiconductor, metal and other surfaces has been studied extensively during the last decades [2]. Although both effects can be described by the same theoretical approach based on the Bradley-Harper model [3], the formation of nanodots has been discovered only very recently [4].
In the presented work, the evolution of GaSb(001) surface under normal incidence ion sputtering has been studied in-situ by surface sensitive X-ray techniques. The Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Grazing Incidence Diffraction (GID) measurements have been performed at the beam line ID01 at the ESRF. These techniques were used to study the temporal evolution of the dots for ion energies from 100 to 1000 eV. With GISAXS the morphology and the correlation of the dots could be observed, with GID information about the dots shape, crystalline structure and present strain was obtained.

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