Review of Refractive Index Refinement Approaches in Atomic and Molecular Physisorption Phenomena in the Case of Thin Mono Layers on a Substrate Materials within Recent Spectroscopic Ellipsometry Improvements

Spectroscopic Ellipsometry (SE) has advanced with integrated photonic no-moving-part designs, enhancing accuracy. Recent developments include IoT integration and cloud protocols (HTTP, MQTT), enabling automatic, remote control and analysis. SE serves as a versatile "Swiss knife" tool, optimized further with AI for full automation and deep learning.It is crucial for studying deposited or molecular beam epitaxy-grown monolayers, facing challenges in thickness and refractive index determination. It finds applications in biology and protein adsorption. SE competes with Surface Plasmon Resonance (SPR) in refractive index precision (~10^-3 to 10^-4).<br/>In situ SE acts as real-time process control, though very thin layer measurements often lack simultaneous thickness and refractive index correlation. This paper revisits P. Drude equations, approximating ellipsometry for ultra-thin layers with a first-order Taylor expansion.During growth or deposition involving atomic layers, SE excels. Unlike SPR, SE using discrete wavelengths offers broader applications with analytical indices law , enhanced by stable vacuum chamber configurations for precise refractive index and thickness measurements. Depolarization factor considerations give additional value, and SE's "no moving part" photonics provide superior capability over SPR, ideal for ALD, MBE, CVD, and PVD techniques.The instruments, while broad in spectroscopic range and angle techniques, face challenges detecting monolayers and ultra-thin layers. Ongoing advancements promise to address these limitations, reinforcing SE as a powerful tool for research and practical applications.This letter explores the future expanding capabilities and applications of SE, highlighting its pivotal role in advancing multi-technology tools.