Unraveling Sub‐Nanostructure Variability in Amorphous Silicon: Mechanisms of Short‐Range Order and Defect Dynamics via In Situ Raman Spectroscopy

Abstract Quantitatively probing sub‐nanometer elementary structural units of amorphous materials, such as amorphous silicon (a‐Si), is essential for Si‐based technological progress. However, accurately identifying and quantifying short‐range order (SRO) and dangling bond/floating bond (DB/FB) defects over a large area in a‐Si remains largely unexplored. Here, it is demonstrated that both the SRO and DB/FB defects at the sub‐nanometer scale can be quantitatively characterized using Raman spectroscopy. Multi‐wavelength lasers (450, 514, and 635 nm) are employed to modulate the sub‐nanometer structures in a‐Si films. Using in situ and ex situ Raman spectroscopy, structural evolution is tracked and changes in the Raman band at ∼ 480 cm⁻¹ (ω 480 ) are investigated. These results reveal distinctly different effects of DB and FB defects on ω 480 , which arise from defect‐induced interfacial stress changes at the Continuous Random Network (CRN)‐SRO interface. An analytical model is established to extract SRO dimensions and DB/FB defect densities from Raman spectra. These research findings deepen the understanding of sub‐nanometer scale structures in amorphous materials and provide crucial methodological foundations for structural characterization and property modulation, showing promise for performance optimization and breakthroughs in amorphous material‐based optoelectronic devices, especially those integrated with Si‐based structures for cutting‐edge applications.