X-ray scattering studies of nanodot pattern formation on semiconductor surfaces by low energy ion beam sputtering

We show the capability of in-situ and ex-situ grazing-incidence small angle X-ray scattering (GISAXS) and diffraction (GID) techniques, using synchrotron radiation, to study the formation of self-organized nanodot patterns on semiconductor targets by ion beam sputtering (IBS). Particularly, surface nanopatterns of short-range hexagonal arrays of nanodots (as observed by atomic force microscopy imaging) were produced on Si(001) and GaSb(001) using low-energy (below or around 1 keV) Ar+ IBS under normal incidence. As an illustrative example of ex-situ application, we present the influence of the surface temperature on the pattern formation on Si(001), where the combination of GID and GISAXS allows to separate between amorphous and crystalline contributions. The ion-induced amorphization and progressive loss of the nanodot pattern with increasing temperature are discussed. In the case of in-situ formation, the authors illustrate real-time monitoring of the process for GaSb(001) surfaces, using GISAXS and a specially designed IBS chamber. Here, pattern coarsening and stabilization is discussed as a function of the ion energy. These results have technological implications, regarding the control over the pattern characteristics and also provide relevant information to the theoretical understanding of pattern formation by IBS.