Studying Thin Ge films and Ge/GeO2 interfaces by means of raman–brillouin scattering
Résumé
The high frequency acoustic phonons employed in Raman–Brillouin scattering are used to probe native oxide layers on Ge film surfaces in GeO2/Ge/InxGa1–xAs heterostructures. The thermal instability of GeO2 results in the production of GeO gas on Ge surfaces; molecules of this gas evaporate through the porous GeO2 layers. As a result, the Ge/GeO2 interface is depleted of Ge, and a sub-stoichiometric GeOx layer is formed. By comparing photoelastic modeling and experimental results, we discovered a 0.5 nm thick interfacial region between the film and the oxide, demonstrating the sensitivity of acoustic phonons to the subnanometer scale. © 2015, Allerton Press, Inc.