Optical Dispersion and Dielectric Analysis of Sputtered Cr 2 O 3 Thin Films for Optoelectronic Applications

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Abstract
Chromium oxide thin films were deposited by DC magnetron sputtering under varying oxygen flow rates (14%–24%). This study evaluates the properties of both the as‐deposited and the post‐annealed samples. X‐ray diffraction (XRD) confirms the evolution from amorphous to crystalline Cr 2 O 3 and reduced structural disorder after thermal annealing. Optical measurements show bandgap values of ~2.70 eV for the as‐deposited films, increasing to ~3.07 eV after annealing due to decreased localized states and improved long range order. A significant decrease in Urbach energy was observed, from ~680 to ~390 meV, which indicate the reduced defects and localized states. Dielectric loss, optical conductivity, surface energy loss function (SELF), and volume energy loss function (VELF) progressively decrease with increasing oxygen flow and exhibit additional reduction upon annealing, reflecting improved film densification and enhanced optical stability. Photoluminescence (PL) spectra exhibit intrinsic Cr 3+ transitions in the ~399–550 nm range, while Hall measurements demonstrate a stable p‐type conduction with annealing effectively lowering the resistivity to 3–9 Ω·cm and increasing carrier density up to 10 18 cm −3 .

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