Confinement creates a 9 GPa ambience: emergence of cristobalite phases in a silica film. (2nd June 2021)

• Record Type: Journal Article
• Authors: Pramanik, Subrata; Ghosh, Jiten; Chanda, Dipak Kumar; Mukhopadhyay, Mrinmay Kumar; Datta, Alokmay
• Is Part Of: Materials research express. Volume 8:Number 6(2021)
• Publication Date: 2021-06-02
• Subjects: silica film -- cristobalite phase -- XRD -- XPS -- SIMS -- FE-SEM -- x-ray reflectivity; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/ac045b
• Languages: English
• ISSNs: 2053-1591

Abstract

Abstract: We present here the results of the x-ray fluorescence (XRF), x-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Analysis of x-rays (EDAX), x-ray Reflectivity (XRR), Secondary Ion Mass spectroscopy (SIMS) and x-ray Diffraction (XRD) studies of silica films spin-coated from a Tetraethyl Orthosilicate (TEOS) precursor on native and hydrophilized Al substrates. It is observed that the substrates are mainly porous (porosity ∼ 33%) AlO(OH), there is a diffuse interlayer of highly porous (porosity ∼ 90%) AlO(OH), essentially a modification of the substrate, and a top layer of silica composed of nanocrystals with in-plane dimensions of 100–300 nm and thickness of 2.5 nm with a sharply defined silica-hydrated alumina interface. The silica nanocrystals were found in the metastable high pressure cristobalite phases with the tetragonal or α -phase co-existing in its low (0.77 GPa) and high (9 GPa) pressure structures. This indicates a high normal stress developed from the confinement and provides a basis for the quantitative assessment of the confinement force, which comes out to be higher in value than the van der Waals force but weaker than the Hydrogen bonding force.