Microstructural and optical studies of La₂O₃ thin films prepared using pulsed laser deposition technique

Abstract

Lanthanum oxide (La₂O₃) thin films were successfully synthesized by the pulsed laser deposition (PLD) technique using a sintered La₂O₃ target prepared with a PVA binder. The structural, morphological, vibrational, and optical characteristics were systematically examined to evaluate their suitability for optoelectronic applications. X-ray diffraction confirmed a polycrystalline hexagonal A-type La₂O₃ structure with average crystallite sizes ranging from 20–30 nm and lattice parameters a = 3.94 Å, c = 6.13 Å. Atomic force microscopy revealed a compact granular surface with uniform topography (Sa = 30.17 nm, Sq = 38.34 nm), indicating homogeneous grain growth. FTIR and Raman spectra identified the fundamental La–O stretching vibrations at ~550–600 cm⁻¹, confirming phase purity and the absence of hydroxyl or carbonaceous impurities. Optical characterization demonstrated high transparency (~74 % in the visible range) and strong UV absorption, with a direct optical band gap of 3.81 eV. The extinction coefficient decreased from 5×10⁻¹³ to 1×10⁻¹³ across the visible region, highlighting low optical losses. The integration of structural, morphological, and optical analyses establishes a clear correlation between PLD parameters and film quality. The obtained results underscore the potential of PLD-grown La₂O₃ films as high-k dielectrics, UV-transparent layers, and thermally stable coatings for advanced optoelectronic and photonic devices.