Correlation between Optical Properties and Chemical Composition of Sputter- Deposited Germanium Oxide (geox) Films (postprint)

Germanium oxide (GeOx) films were grown on (100) Si substrates by reactive Direct-Current (DC) magnetron sputter-deposition using an elemental Ge target. The effects of oxygen gas fraction, U = O2/ (Ar + O2), on the deposition rate, structure, chemical composition and optical properties of GeOx films have been investigated. The chemistry of the films exhibits an evolution from pure Ge to mixed Ge + GeO + GeO2 and then finally to GeO2 upon increasing U from 0.00 to 1.00. Grazing incidence X-ray analysis indicates that the GeOx films grown were amorphous. The optical properties probed by spectroscopic ellipsometry indicate that the effect of U is significant on the optical constants of the GeOx films. The measured index of refraction (n) at a wavelength (k) of 550 nm is 4.67 for films grown without any oxygen, indicating behavior characteristic of semiconducting Ge. The transition from germanium to mixed Ge + GeO + GeO2 composition is associated with a characteristic decrease in n (k = 550 nm) to 2.62 and occurs at U = 0.25. Finally n drops to 1.60 for U = 0.50–1.00, where the films become GeO2. A detailed correlation between U, n, k and stoichiometry in DC sputtered GeOx films is presented and discussed. Published by Elsevier B.V.