Growth-dependent refractive index nonlinearity and mean microstructural properties of codeposited composite gadolinia silica films

Abstract

Codeposited gadolinia silica composite films have been probed for their growth-dependent optical and microstructural properties using phase-modulated spectroscopic ellipsometry and scanning probe microscopy. The mean refractive indices were computed using an effective ellipsometric multilayer modeling approach. Most of the composite films have shown growth-induced nonlinear refractive indices to some extent. However, the mean optical properties have depicted interesting trends in the microstructural evolutions. Gadolinia silica composite films in the composition ratio ranging from 90:10 to 70:30 have depicted superior optical as well as morphological properties. Unlike conventional oxide films, these composite films displayed microstructural, spectral refractive index, and bandgap supremacy over the pure films. Such an observation cannot be explained by the empirical Moss law. Atomic force microscopy also revealed a superior morphology in the composite films. The autocorrelation and height-height correlation functional analysis have distinctly supported such superior microstructural features in the composite films, which justifies the supremacy of the optical properties. Such an observation has opened up possibilities to utilize such composite films toward deep-and extreme-ultraviolet spectral regions of the electromagnetic spectrum.