Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle x-ray scattering

Atomic layer deposition (ALD) enables the conformal coating of porous materials, making the technique suitable for pore size tuning at the atomic level, e.g., for applications in catalysis, gas separation and sensing. It is, however, not straightforward to obtain information about the conformality of ALD coatings deposited in pores with diameters in the low mesoporous regime (< 10 nm). In this work, it is demonstrated that in situ synchrotron based grazing incidence small angle x-ray scattering (GISAXS) can provide valuable information on the change in density and internal surface area during ALD of TiO2 in a porous titania film with small mesopores (3-8 nm). The results are shown to be in good agreement with in situ x-ray fluorescence data representing the evolution of the amount of Ti atoms deposited in the porous film. Analysis of both data sets indicates that the minimum pore diameter that can be achieved by ALD is determined by the size of the Ti-precursor molecule

In situ study of ALD processes using synchrotron-based X-ray fluorescence and scattering techniques

In this paper, we present an x-ray based approach for in situ characterization during ALD processes. In a first case study the growth of HfO2 on H-terminated and oxidized Si and Ge surfaces is studied. X-ray fluorescence (XRF) is used to monitor the amount of deposited Hf atoms, while grazing incidence small angle x-ray scattering (GISAXS) provides information on the evolution of surface roughness. A second case study concerns the growth of TiO2 in a porous titania film containing ink-bottle mesopores. XRF and GISAXS measurements are used to monitor the Ti uptake and the density of the porous film, respectively

Tuning the Pore Size of Ink-Bottle Mesopores by Atomic Layer Deposition

Tuning the Pore Size of Ink-Bottle Mesopores by Atomic Layer Depositio