Thickness dependent crystallinity, hydrophilicity, and surface microtexture in CaF2 thin films deposited via thermal evaporation method

Abstract

This study investigates the deposition and characterization of CaF₂ thin films with thicknesses ranging from 40 to 320 nm, fabricated via thermal evaporation onto glass substrates. X-ray diffractometry (XRD) revealed that increased film thickness leads to enhanced crystallinity, with larger crystallite sizes and reduced lattice strain. Wettability analysis demonstrated a transition from hydrophobic behavior (contact angle ∼70° for 40 nm) to hydrophilic behavior (contact angle ∼52° for 320 nm) as film thickness increased. Surface morphology, examined via atomic force microscopy (AFM), showed a significant reduction in surface roughness in thicker films, with smoother, more coalesced surfaces observed for films over 160 nm. Monofractal analysis further confirmed the evolution of surface microtexture, with thicker films exhibiting higher uniformity and reduced surface complexity. These findings provide critical insights into optimizing CaF₂ thin films for applications in optics, electronics, and surface coatings, where improved crystallinity and surface properties are essential.