Abstract
We discuss the design and performance of a transition edge sensor (TES) X-ray microcalorimeter array for scanning transmission electron microscope (STEM)–energy dispersive X-ray spectroscopy (EDS). The TES X-ray microcalorimeter has better energy resolution compared to conventional silicon drift detector and STEM–EDS utilizing a TES detector makes it possible to map the distribution of elements on a specimen in addition to analyze the composition. The requirement for a TES detector is a high counting rate (\(>\)20 kcps), wide energy band (0.5–15 keV) and good energy resolution (\(<\)10 eV) full width at half maximum. The major improvement of this development is to increase the maximum counting rate. In order to accommodate the high counting rate, we adopted an \(8 \times 8\) format, 64-pixel array and common biasing scheme for the readout method. We did all design and fabrication of the device in house. With the device we have fabricated most recently, the pulse decay time is 40 \(\upmu \)s which is expected to achieve 50 kcps. For a single pixel, the measured energy resolution was 7.8 eV at 5.9 keV. This device satisfies the requirements of counting rate and energy resolution, although several issues remain where the performance must be confirmed.
Highlights
An energy dispersive X-ray spectroscopy (EDS) performed with electron microscopes plays an important role for nanoscale compositional analysis in various fields such as material science and biotechnology
When we introduced a single pixel transition edge sensor (TES) detector for scanning transmission electron microscope (STEM), we could achieve an energy resolution of 8.9 eV [4]
When we considered the wiring space and the focal spot size of the polycapillary [6], which was used in this system to increase the solid angle, the maximum area where TES detector can occupy is limited to under 7 × 7 mm2
Summary
An EDS performed with electron microscopes plays an important role for nanoscale compositional analysis in various fields such as material science and biotechnology In this experiment, an electron beam is directed to a specimen and the elements in the specimen are determined by measuring the energy of their characteristic X-rays. Because the maximum counting rate of our single pixel TES X-ray microcalorimter is about 300 cps, we adopted an 8 × 8 format, 64 pixel-array. The properties of R(T ) and IV-curves, transition temperature, pulse decay time, energy resolution, saturation energy, and the performance of TES with high counting rate. We did the RT and IV measurement and X-ray irradiation test to confirm the performances of this device
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