Search for: All records

Continued advances in superconducting qubit performance require more detailed understandings of the many sources of decoherence. Within these devices, two-level systems arise due to defects, interfaces, and grain boundaries and are thought to be a major source of qubit decoherence at millikelvin temperatures. In addition to Al, Nb is a commonly used metallization layer in superconducting qubits. Consequently, a significant effort is required to develop and qualify processes that mitigate defects in Nb films. As the fabrication of complete superconducting qubits and their characterization at millikelvin temperatures is a time and resource intensive process, it is desirable to have measurement tools that can rapidly characterize the properties of films and evaluate different treatments. Here, we show that measurements of the variation of the superconducting critical temperature Tc with an applied external magnetic field H (of the phase boundary Tc−H) performed with very high-resolution show features that are directly correlated with the structure of the Nb films. In combination with x-ray diffraction measurements, we show that one can even distinguish variations in the size and crystal orientation of the grains in a Nb film by small but reproducible changes in the measured superconducting phase boundary.

Layered 2D (PbI₂)_1−x(BiI₃)_xmaterials exhibit a nonlinear dependence in structural and charge transport properties unanticipated from the combination of PbI₂and BiI₃. Within (PbI₂)_1−x(BiI₃)_xcrystals, phase integration yields deceptive structural features, while phase boundary separation leads to new conductance switching behavior observed as large peaks in current during current–voltage (I–V) measurements (±100 V). Temperature‐ and time‐dependent electrical measurements demonstrate that the behavior is attributed to ionic transport perpendicular to the layers. High‐resolution transmission electron microscopy reveals that the structure of (PbI₂)_1−x(BiI₃)_xis a “brick wall” consisting of two phases, Pb‐rich and Bi‐rich. These brick‐like features are 10s nm a side and it is posited that iodide ion transport at the interfaces of these regions is responsible for the conductance switching action.