Chemical and structural investigation of the role of both Mn and Mn oxide in the formation of manganese silicate barrier layers on SiO₂

In this study, Mn silicate (MnSiO₃) barrier layers were formed on thermally grown SiO₂ using both metallic Mn and oxidized Mn films, in order to investigate the role of oxygen in determining the extent of the interaction between the deposited Mn and the SiO₂ substrate. Using x-ray photoelectron spectroscopy, it has been shown that a metallic Mn film with an approximate thickness of 1 nm cannot be fully converted to Mn silicate following vacuum annealing to 500 °C. Transmission electron microscopy (TEM) analysis suggests the maximum MnSiO₃ layer thickness obtainable using metallic Mn is ∼1.7 nm. In contrast, a ∼1 nm partially oxidized Mn film can be fully converted to Mn silicate following thermal annealing to 400 °C, forming a MnSiO₃ layer with a measured thickness of 2.6 nm. TEM analysis also clearly shows that MnSiO₃ growth results in a corresponding reduction in the SiO₂ layer thickness. It has also been shown that a fully oxidized Mn oxide thin film can be converted to Mn silicate, in the absence of metallic Mn. Based on these results it is suggested that the presence of Mn oxide species at the Mn/SiO₂ interface facilitates the conversion of SiO₂ to MnSiO₃, in agreement with previously published studies.