Anomalous grazing-incidence small-angle X-ray scattering of Ga₂O₃-based nanoparticles

Grazing-incidence small-angle X-ray scattering (GISAXS) performed at several X-ray energies in the vicinity of the absorption edge of a considered element is called anomalous GISAXS (AGISAXS). This emerging technique takes advantage of the variation of the scattering factor near an absorption edge, allowing the morphology of multi-component nanomaterials to be unraveled. The selected model system for AGISAXS simulations is mainly an In₂O₃ layer containing Ga₂O₃-based nanoparticles. The transmission coefficients at the different X-ray energies near the Ga K edge are identical at one specific incident angle (near the critical angle). Hence, it could be relevant to perform AGISAXS at this incident angle in order to cancel the transmission modification as the X-ray energy changes. For buried nanoparticles, grazing-incidence effects are negligible with respect to the anomalous element-specific contribution provided that the experiments are performed at energies a few electronvolts below the absorption edge. Interestingly, AGISAXS has a clearly different intensity behavior versus X-ray energy for an embedded monodisperse spherical particle, a hole and a core–shell particle. Hence, AGISAXS can be used to unambiguously distinguish such embedded particles. Moreover, even for a dense layer of core–shell nanoparticles on a substrate, anomalous effects are much larger than grazing effects as the X-ray energy changes. Finally, it is shown that experimental anomalous scattering can be significant and can be satisfactorily simulated.