Optical properties of highly reduced SrTiO3-x

The reflectance of highly reduced SrTiO3-x has been studied in samples where the carrier concentration—or oxygen-vacancy density — varies from about 1018 to 1021 cm-3. Several phonon modes are strongly influenced by oxygen-vacancy density. Oxygen reduction induces a mid-infrared band whose oscillator strength scales with carrier density. In highly reduced samples, a weakly localized plasmon mode develops.