Reactive intercalation and oxidation at the buried graphene-germanium interface

We explore a number of different electrochemical, wet chemical, and gas phase approaches to study intercalation and oxidation at the buried graphene-Ge interface. While the previous literature focused on the passivation of the Ge surface by chemical vapor deposited graphene, we show that particularly via electrochemical intercalation in a 0.25 N solution of anhydrous sodium acetate in glacial acetic acid, this passivation can be overcome to grow GeO2 under graphene. Angle resolved photoemission spectroscopy, Raman spectroscopy, He ion microscopy, and time-of-flight secondary ion mass spectrometry show that the monolayer graphene remains undamaged and its intrinsic strain is released by the interface oxidation. Graphene acts as a protection layer for the as-grown Ge oxide, and we discuss how these insights can be utilized for new processing approaches.