Oxidation resistance of thin boron carbo-nitride films on Ge(100) and Ge nanowires

Chemical vapor deposition of thin (< 10 nm) films of amorphous boron carbo-nitride (BC0.7N0.08, or BCN) on Ge(100) and Ge nanowire (GeNW) surfaces was studied to determine the ability of BCN to prevent oxidation of Ge. X-ray photoelectron spectroscopy was used to track Ge oxidation of BCN-covered Ge(100) upon exposure to ambient, 50 °C deionized water, and a 250 °C atomic layer deposition HfO2 process. BCN overlayers incorporate O immediately upon ambient or water exposure, but it is limited to 15% O uptake. If the BCN layer is continuous, the underlying Ge(100) surface is not oxidized despite the incorporation of O into BCN. The minimum continuous BCN film thickness that prevents Ge(100) oxidation is ~ 4 nm. Thinner films (≤ 3.2 nm) permitted Ge(100) oxidation in each of the oxidizing environments studied. GeNWs with a 5.7 nm BCN coating were resistant to oxidation for at least 5 months of ambient exposure. High resolution transmission electron microscopy images of HfO2/BCN/Ge(100) cross-sections and BCN-coated GeNWs reveal clean, abrupt BCN–Ge(100) interfaces.