In-situ X-Ray Diffraction of GaSb Nanopatterned by Normal Incidence Sputter Erosion

Low energy ion erosion of surfaces can lead to the formation of self-organized structures in the range from 10 to 100 nm [1]. Periodic ripple patterns and hexagonally ordered dot arrays can be achieved for oblique and normal incidence, respectively. The evolution of ripple structures on different materials has been studied extensively during the last decades whereas the formation of dots has been discovered only recently [2] and is not fully understood yet.
In the presented work, the evolution of GaSb(001) surface morphology under normal incidence 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 evolution of the dots for ion energies from 100 to 1000 eV. With GISAXS the morphology and the correlation of the dots is analysed, while in GID information about the crystalline structure (i.e. strain) is added. This way, three regimes are observed and identified as smoothing, pattern formation and increase of lateral order.

[1] M. Navez, D. Chaperot and C. Sella, C. R. Acad. Sci. 254 (1962), 240
[2] S. Facsko et al., Science 285 (1999), 1551