NEAR-ULTRAVIOLET OPTICAL-ABSORPTION IN SPUTTER-DEPOSITED CUBIC YTTRIA

Cubic yttria films were sputter deposited on unheated fused silica substrates. In situ optical spectrometry was used to monitor emission from six YI transitions in the discharge. A simple formalism was developed for estimating the ratio of yttrium arriving at the substrate in atomic form to yttrium bonded to oxygen in an unspecified molecular form. The optical absorption coefficient (α=∼103-105 cm-1) of the films was determined, post-deposition, over the energy range 5.0-6.2 eV. The results show that a large atomic yttrium flux to the substrate during deposition resulted in a ''disordered" optical absorption edge. A large flux of yttrium bonded to oxygen resulted in an edge with two direct interband transitions separated by 0.66 eV, in good agreement with the bulk single crystal ε2 data and a recent theoretical energy band calculation for cubic yttria.