FEI Themis Z Advanced Probe Aberration Corrected Analytical TEM/STEM

The FEI Themis Z is and advanced analytical scanning/transmission electron microscope (STEM/TEM) from Thermo Fisher Scientific Company that operates between the electron energy of 60 to 300 keV with a Schottky electron emitter, an electron energy monochromator, and a 5th order probe spherical aberration corrector. The microscope is additionally equipped for chemical analysis using highly efficient and fast electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDS) systems.

This instrument will meet the research needs of electron imaging and chemical analysis in materials research. Specifically, the microscope enables imaging and chemical mapping in 2D and 3D at atomic or nanoscales by providing following research capabilities: 1) performing low voltage spectral analysis for molecules and single atoms using EELS, 2) conducting ultra-sensitive mapping of local bonding and oxidation states using EELS, and 3) analysis of composition and crystallographic orientation in 2D and 3D using EDS.

In addition to the acoustic enclosure that comes with the instrument, a custom-designed metal room was built around the whole microscope to ensure proper cancellation of electromagnetic fields that would negatively affect the performance of the instrument. The structure, called MuROOM, from Magnetic Shield Co., uses metal layers including a nickel-iron alloy sheet to shield fields that would affect, for instance, the high energy resolution required for the analytical capabilities of the instrument. The MuRoom was featured in this article.

Feature Highlights:

• Acoustic enclosure and remote operation, enabling acoustic and temperature variation damping during operation
• Accelerating voltage: 60 -300 kV
• Electron source: High brightness Schottky field emission electron source (X-FEG)
• Integrated electron source energy monochromator for beam energy widths to <150meV
• Probe forming optics include an advanced 4th order (5th order optimized) spherical aberration corrector (DCOR)
• Probe corrector tunings at 60, 80, and 300 kV
• STEM resolution: ranging from <60pm at 300kV to  <120pm at 60 kV
• Greater than 100 pA probe currents available in a 1 angstrom electron probe
• High Angle Annular Dark Field (HAADF) detector and on-axis bright field/dark field STEM detector
• Integrated Differential Phase Contrast (iDPC) for light element (low Z) imaging
• Simultaneous collection of BF/ABF/DF and HAADF images on the system
• TEM mode: information transfer of 60pm at 300kV to 100pm at 60kV
• Gatan Quantum ER/965 GIF with Ultrafast Dual EELS (Electron Energy Loss Spectroscopy) Spectrum Imaging (1000 spectra/s, energy resolution of 150 meV or better)
• 4-crystal EDS (Energy Dispersive Spectroscopy for X-Rays) detection system (FEI Super-X)
• Large EDS collection solid angle of 0.7 steradians for atomic scale EDS analysis
• EDS compatible with large sample rotation/tilt for 3D EDS tomography
• Constant power magnetic lenses enabling faster mode and accelerating voltage changes switching by eliminating related thermal drift and providing high controllability and reproducibility
• Automated tuning for the monochromator and corrector (OptiMono & OptiSTEM+)
• Computerized 5-axes Piezo enhanced stage
• High-speed, digital search-and-view camera
• FEI Ceta 16M 16-megapixel digital camera for for imaging and diffraction applications
• STEM & TEM tomography acquisition software and high field-of-view single-tilt tomography holder
• Precession electron diffraction

• EMPAD (Electron Microscope Pixelated Array Detector), a pixelated detector for applications as 4D STEM acquiring diffraction pattern in each point of a map at a speed of up to 1,100 diffraction patterns per second. The EMPAD sensor is a 128x128 direct electron detector with pixels of 150 microns in size. It is sensitive to a single electron and has a dynamic range of 30 bits in single shot mode allowing for a maximum detectable current per pixel of 2pA @200kV.

The EMPAD upgrade of this microscope was funded through the Illinois MRSEC NSF Award Number DMR-2309037. Its use should be acknowledged in any published works, with the wording: “The authors acknowledge the use of facilities and instrumentation at the Materials Research Laboratory Central Research Facilities, University of Illinois, partially supported by NSF through the University of Illinois Materials Research Science and Engineering Center DMR-2309037.” Please also send a copy of the publication (email or hard copy), or the publication information (citation, DOI, or conference name and paper/poster title) to mrl-facilities@illinois.edu.