Persistence of the Nb(100) surface oxide reconstruction at elevated temperatures

Helium atom scattering and Auger electron spectroscopy (AES) are used to characterize the (3 × 1)-O reconstruction of the Nb(100) surface at elevated temperatures. Persistent helium diffraction peaks and specular lineshape analysis indicate that the oxide structure persists, apparently unchanged, until surface temperatures of at least 1130 K. In a complementary experiment, AES oxygen to niobium ratios for Nb(100) show little to no change when the surface temperature is varied from 300 K to 1150 K. These data inform future development of superconducting radio frequency (SRF) cavities. In particular, these findings demonstrate the important role that persistent niobium oxides will play in the optimization of thin film growth strategies and coating procedures for Nb3Sn and other next-generation SRF superconducting alloy materials.