Apparatus for real time in situ quantitative studies of growing nanoparticles by grazing incidence small angle X-ray scattering and surface differential reflectance spectroscopy

Abstract

This paper describes an experimental setup that was developed to simultaneously perform grazing incidence small angle X-ray scattering (GISAXS) and surface differential reflectance spectroscopy (SDRS) measurements in ultra-high vacuum, in situ, during the three-dimensional growth of islands on a substrate, from the very beginning of the growth up to coalescence in the film. Four major features of this new GISAXS setup are: (i) the absence of window between the X-ray source and the sample, thus avoiding any unwanted background scattering; (ii) the use of a high grade two-dimensional CCD detector; (iii) very high flux from an ESRF undulator beamline; (iv) the ability to subtract the reference from the bare substrate before deposit. This results in two-dimensional measurements that are background-free and extend over a very large intensity dynamic of a few 10 4. This allows for the first time to perform measurements on very small deposits (as low as 0.01 nm of equivalent thickness) and to record measurements in real time without interrupting the growth process. Two softwares have been developed and can be freely downloaded from the WEB in order to perform a very detailed quantitative analysis of the both GISAXS and SDRS data, allowing to probe the island size and separation from 1 to ∼50 nm.