Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content

We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.This work has been partially supported by MINECO (Spain) grants FIS2012-38866-C05-05 and MAT2013-47878-C2-1-R, and the Spanish Government (Project ENARDECEL50 TEC2014-54260-C3-2-P), as well as by the Comunidad Autónoma de Madrid (Project NANOAVANSENS S2013/MIT-3029). TEM work has been conducted at the LABMET laboratory, associated with Red de Laboratorios of CAM, Spain, and also at LANE-Cinvestav in Mexico City. A.R.C. acknowledges funding from the Juan de la Cierva program (Spain) under contract no. JCI-2012-14509; KL acknowledges funding from FCT (Portugal) through the program Investigador FCT