Substraadi

Substraadi is a term used in materials science to describe the interfacial region directly adjacent to a substrate during thin-film deposition and related surface processes. It refers to a chemically and structurally distinct layer that forms at the interface between the substrate and the overlayer, rather than to the bulk substrate itself.

Substraadi does not denote a separate material with a fixed composition; its properties depend on processing conditions, such as temperature, deposition rate, ambient gas, and substrate chemistry. Its thickness typically spans a few atomic layers to several nanometers. The substraadi can exhibit altered bonding, composition gradients due to interdiffusion, and surface reconstruction, which can influence adhesion, epitaxial growth, and barrier properties.

Formation mechanisms include interdiffusion of substrate and adatoms, chemical reactions at the interface, oxidation or contamination, and strain-driven rearrangements. The substraadi may act as a diffusion barrier or as a conduit for strain relaxation, affecting nucleation energetics and film morphology.

Characterization of the substraadi employs techniques such as X-ray photoelectron spectroscopy, transmission electron microscopy with interface imaging, secondary ion mass spectrometry, low-energy electron diffraction, and spectroscopic ellipsometry. The concept assists researchers in modeling interfacial phenomena and improving control over adhesion, corrosion resistance, catalysis, and electronic properties in layered materials.

Etymology and usage: the term substraadi appears in discussions of interfacial science and thin-film technology as a designation for the interfacial zone near a substrate. It is used to distinguish the immediate interface region from the bulk substrate and the overlayer material. See also interfacial layer, epitaxy, and diffusion.