Y.E. Chen

Cross‐sectional TEM analysis of fault and slip structures produced during etching processes for large‐scale superconducting‐tunnel‐junction array detectors

We proposed a model of fault and slip formation to explain the excessive increase of the leak current of Nb/Al superconducting tunnel junction detectors and the nano‐structural deformation. Observations of the cross‐sections at pinpoint places in the array detectors with transmission electron microscopy (TEM) support our model. The nano‐scale tectonism due to the relaxation of the residual stress in the sputtered films, which corresponds to a wafer bend motion at a few tens nm at 10 mm‐apart two points, generates the vertical fault in the Nb/Al film and the slip plane in the 1 nm‐thick AlOx tunneling layer. The slip in the AlOx layer can cause the leak current increase.

Charge-Number Discrimination Mass Analysis Using Superconducting Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometer -Analysis of Fragment Impurities in Immunoglobulin G-

Conventional time-of-flight mass spectrometers equipped with microchannel plate (MCP) detectors give only m/z values, which remains ambiguous over charge number (z). In contrast, the matrix-assisted laser desorption/ionization (MALDI) TOF mass spectrometer (TOF-MS) with a superconducting tunnel junction (STJ) detector—Super-TOF-MS—enables kinetic energy measurement with mass-independent detection efficiency. Therefore, since kinetic energy is proportional to z, it is possible to determine mass (m) unambiguously.The Super-TOF-MS is effective for analysing high-mass fragments in immunoglobulin solution. Specifically, unknown peaks appearing on mass spectra for immunoglobulin G (IgG) samples can be identified as IgG fragments using kinetic energy measurements and the mass-independent detection efficiency of the STJ detector. A complete IgG molecule has two heavy and two light chains that are connected by disulfide bonds. The heavy and light chains include four and two structural domains, respectively (12 domains in total). The charge-state discrimination mass analysis enables the assignment of m values to the unknown peaks. The existence of pairs for which the m-value sum is equal to that of the intact IgG reveals that there are several fragment types consisting of different numbers of structural domain units.