Search

Scanning superconducting quantum interference device (sSQUID) microscopy is currently one of the most effective methods for direct and sensitive magnetic flux imaging on the mesoscopic scale. A SQUID-on-chip (SOC) design allows integration of field coils for susceptometry in a gradiometer setup which is very desirable for measuring magnetic responses of quantum matter. However, the spatial resolution of such a design has largely been limited to micrometers due to the difficulty in approaching the sample. Here, we used electron beam lithography technology in the fabrication of the 3D nano-bridge-based SQUID devices to prepare pick-up coils with diameters down to 150 nm. Furthermore, we integrated the deep silicon etching process in order to minimize the distance between the pick-up coil and the wafer edge. Combined with a tuning-fork-based scanning head, the sharpness of the etched chip edge enables a precision of 5 nm in height control. By scanning measurements on niobium chessboard samples using these improved SQUID devices, we demonstrate sub-micron spatial resolutions in both magnetometry and susceptometry, significantly better than our previous generations of nano-SQUIDs. Such improvement in spatial resolution of SOC is a valuable progress for magnetic imaging of quantum materials and devices in various modes. [ABSTRACT FROM AUTHOR]

The effective elastic properties of carbon fibre reinforced silicon carbide composite (C/SiC) with multilayered matrix manufactured by chemical vapour infiltration method are studied in the present paper. Based on the material tomography of scanning electron microscopy, distributions of voids and microcracks are identified and taken into account in the finite element model of such C/SiC composite. It is shown the proposed two scale finite element models of multilayered C/SiC composites can characterise physically the real situation of involved voids and microcracks related to the chemical vapour infiltration process. The numerical results of effective moduli and experimental ones have a reasonable agreement. [ABSTRACT FROM AUTHOR]