Optical properties of Al₂O₃ thin films grown by atomic layer deposition

We employed the atomic layer deposition technique to grow Al(2)O(3) films with nominal thicknesses of 400, 300, and 200 nm on silicon and soda lime glass substrates. The optical properties of the films were investigated by measuring reflection spectra in the 400-1800 nm wavelength range, followed by numerical fitting assuming the Sellmeier formula for the refractive index of Al(2)O(3). The films grown on glass substrates possess higher refractive indices as compared to the films on silicon. Optical waveguiding is demonstrated, confirming the feasibility of high-index contrast planar waveguides fabricated by atomic layer deposition.