Fig. 2: Material analyses of superconducting MgB2 films.
From: Single-photon detection using large-scale high-temperature MgB2 sensors at 20 K
a Atomic-force microscope (AFM) image of the surface topography of a MgB2 film (sample F180, Supplementary Fig. 1). The root-mean-square (RMS) surface roughness over several micrometers was less than 1 nm. b Cross-section of thin MgB2 film taken via scanning transmission electron microscopy (STEM). Using focused-ion beam (FIB) preparation, a cross-section of the material was transferred onto a suitable TEM grid. The presence of carbon on top of the film is a result of the sample preparation. c Energy-Dispersive X-ray Spectroscopy (EDS) for elemental characterization of Si, Mg, and O. The EDS spectrum provides the compositional information for the deposited MgB2 films. Notably, the superconducting MgB2 core is sandwiched between two oxides. While the MgB2 films readily pick up oxygen from the ambient atmosphere forming oxides on the top, the presence of O2 at the interface is likely from residual SiOx on the SiC substrate surface.
