The Nion UltraSTEM 100 is an aberration corrected STEM that offers sub-angstrom resolution at both 100 keV and 60 keV. The Nion can also run at 30keV and 40KeV with near 1Å resolution. A special monochromater offers ultra-fast ELLS spectra at energy resolution better than 10 meV (0.01 eV).
The instrument is part of ASU's Southwestern Center for Aberration Corrected Electron Microscopy. The instrument's flexible column provides < 1 Å resolution imaging as well as rapid nanoanalysis with an atom-sized electron probe containing >0.5 nA of current, and efficient coupling into a variety of detectors.
The UltraSTEM has produced atomic-resolution elemental maps in less than a minute and has also produced unsurpassed images of graphene and similar light-Z materials, while operating at 60 keV, below the knock-on threshold for C and other light atoms.
The principal design elements of the UltraSTEM that have made this advance possible are:
- High-brightness cold field emission electron gun (CFEG)
- High-performance 3rd generation C3/C5 aberration corrector
- Ultra-stable sample stage using detachable sample cartridge
- Optimized EELS coupling optics
- UHV construction
- Complete remote operability, including sample exchange
- A direct electron detector for EELS collection (to be installed early 2021)
- Operating energies: 100 keV, 60 keV and 30 keV
- Gun brightness: >1x109 A/(cm2 sr) at 100 keV
- Gun vacuum: <5x10-11 torr
- Sample vacuum: typically in 10-9 torr range
- Number of sample cartridges supplied: 3 fixed, 3 tilting
- Tilt range of tilting cartridge: ± 25° (on 2 axes)
- Objective lens (OL) aberration coefficients (with 4 mm gap polepiece, at 100 keV): Cs = 1.1 mm Cc = 1.1 mm
- Probe jitter relative to sample: <0.1 Å r.m.s.
- HT stability: better than 1 ppm/minute
- Energy resolution in EELS spectra (at 60 keV): <10 meV (0.01 eV)
- AC stray field sensitivity: 1 Å probe motion for 1 mG of stray fields (at 50 or 60 Hz and 100 keV)
The Center for High Resolution Electron Microscopy (CHREM) is organized to provide easy access to instruments by campus-wide ASU researchers, as well as external clients. Facility use is a telephone call or e-mail message away.
Most samples can be accommodated in CHREM microscopes. The exception may be those that are particularly hazardous to human health. No radioactive samples, and the sample must survive in a vacuum and under the electron beam.
Manuel Roldan Gutierrez
Associate research scientist
- Aberration corrected TEM/STEM
- Electron Energy Loss Spectroscopy
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