Application of soft X-ray reflectometry for analysis of underlayer influence on structure of atomic-layer deposited SrTi_xO_y films

Graphical abstract: - Highlights: • Density of SrTiO₃ films depends on underlayer material in SrTiO₃/B/Si-ALD systems. • Interface is very abrupt for the sample prepared on Si₃N₄ underlayer. • HfO₂ underlayer leads to formation of wide interface. • SXRR emerges as a tool of atomic analysis at sub-nanometer scale. - Abstract: We explored the possibility to quantify the atomic in-depth distributions by using the energy-dependent soft X-ray reflectivity (SXRR) measurements, in particular, the possibility to obtain the profiles of low-Z elements [C, N, O, Si] in heterostructures containing high concentration of higher-Z atoms [Ti, Sr, Hf]. We have shown that the SXRR technique allows one not only to quantify the atomic composition of the Sr-rich SrTi_xO_y insulators grown on (1 0 0)Si by the Atomic Layer Deposition method but also to obtain atomic profiles across a few-nm thick underlayer (UL) inserted between SrTi_xO_y film and the Si substrate. The accuracy of atomic concentrations and densities estimated is already sufficient to trace even small variations in composition of the SrTi_xO_y grown by ALD on the chemically different underlayers and most it is important the composition and extension of an interfaces