Spectral Analysis of Nanomaterials using a Transition-Edge Sensor Microcalorimeter Mounted on a Field-Emission Scanning Electron Microscope

A prototype transition-edge sensor (TES) microcalorimeter is successfully integrated into a commercial field-emission scanning electron microscope (FE-SEM). The microcalorimeter is composed of a gold (Au) absorber, a Au/Ti bilayer thermometer and a thermal isolation structure with a SiNx membrane. Operating temperatures of 100–150 mK are obtained with a dilution refrigerator. The measured energy resolution was between 19–22 eV for Al Kα at an acceleration voltage of 5 keV. The newly developed system was applied to the analysis of nanosheets for the first time at a low acceleration voltage (≤ 5 kV). The energy dispersive spectrometer (EDS) spectra of Nb3O8 nanosheets of different thicknesses (less than 20 nm) were successfully detected. Moreover, Au particles on carbon nanotubes with a thickness less than 1 nm are detected clearly. With further improvement of both energy resolution and count rate, this system holds the promise for practical X-ray compositional characterization of nanomaterials with high image spatial resolution in the low-acceleration-voltage regime.