Optical Characterization of Silver-Doped Germanium-Chalcogenide Thin Films

The purpose of this research is to optically characterize germanium-based chalcogenide thin films and evaluate how their properties change when the composition is altered. The composition changes based on if the chalcogenide contains selenium or sulfur, if the film is 60 nanometers or 200 nanometers, and if the film is doped with silver (ranging from 0 nanometers to 30 nanometers). These amorphous germanium-chalcogenide thin films exhibit interesting properties when doped with silver, such as transporting ions within the film in addition to electron transport. Using optical characterization techniques such as UV-Vis spectroscopy, profilometry, and ellipsometry, parameters that describe the optical characteristics are found, including the absorption coefficient, refractive index, optical band gap energy, and information on the density of states. This research concludes that as silver content within the film increases, the optical bandgap energy decreases—this is a consistent trend in existing literature. Having a better understanding of the materials’ physical properties will be useful to aid in the creation of microsystems based on these materials by selecting optimal composition and growth conditions. Important applications using these materials are currently being researched, including variable capacitor devices relying on the ionic conductor behavior these materials display. The optical properties like the absorption coefficient and the optical bandgap energy are invaluable in designing these applications effectively.