Optical properties of crystalline Ta2O5 thin films

Abstract

Thin tantalum oxide (Ta2O5) films were prepared on Si(100) substrates using the chemical solution deposition (CSD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), spectrophotometric UV-VIS and ellipsometric measurements were employed to characterize these films. High-quality films of Ta2O5 were obtained by spin coating at 2000, 2250, 2500, 2750 and 3000 rpm during 30 s, and subsequently annealed at 900°C for 15 h. The microstructure and crystallinity of the thin films were analyzed by XRD in preferred (001), (010), (200) orientations, the surface morphology was examined by SEM, and the film thickness was determined by profilometric and ellipsometric measurements, the thin films were heterogeneous. The orthorhombic structure and crystallinity of Ta2O5 thin films on Si(100) substrates were characterized by XRD. The obtained lattice constants are a = 6.117 Å, b = 3.716 Å, c = 4.114 Å. The optical spectrophotometric measurements at λ = 400 nm yielded refractive index values n of 1.81-1.93; from ellipsometric analysis the refractive index values are 1.8-1.94.