Atomic-resolution EELS chemical composition map taken on the Nion UltraSTEM 100 microscope. V = red, La = green, Ti = blue. Yellow arrows point to purple bands showing V/Ti intermixing. This 128x375 pixel spectrum-image was taken at 10ms/pix (~15 min total acquisition) with no drift compensation. (Courtesy L. Fitting-Kourkoutis & D. Muller)

ADF image of monolayer boron nitride containing atomic substitutions. Quantitative analysis of the image produced a detailed atomic model, which is shown superposed on the image. Boron atoms are shown red, carbons atoms yellow, nitrogen atoms green and oxygen atoms blue. Graphic courtesy Tim Pennycook, ORNL & Vanderbilt U.

Nion Electron Microscopes

Nion microscopes have been designed from the “ground up”, all within the last ten years. This has allowed them to avoid having any “historical design baggage” that is typically found in other electron microscopes. The result is an integrated performance second to none.

Nion microscopes have many features not found in other instruments, with benefits that increase productivity and provide opportunities for new kinds of experiments:

Feature	Benefit
>0.5 nA current in an atom-sized probe	Rapid atomic-resolution EELS elemental mapping
Correction of all fifth-order axial aberrations	Larger probe angles, higher beam current
Every operation can be performed remotely	Remote operation with no local assistance
Computer-controlled sample exchange	Samples can be changed by remote users
Up to 5 samples stored in storage chamber	Rapid sample change – no waiting for vacuum to recover
Friction-free, centro-symmetric sample stage	Ultra-precise sample motion, freedom from drift
Double tilt holder with ball bearing mechanics	Ultra-precise sample tilting
Fast electrostatic beam blanker	Avoids sample damage when not collecting data
3rd-order-corrected EELS coupling optics	>50 mr acceptance semi-angles, more efficient analysis
Optional pre-corrector scanning	Aberration-corrected conical illumination scanning
Microscope column is entirely ion-pumped	Minimizes sample contamination and etching
Column uses only metal vacuum seals	Sample vacuum typically <1x10^-9 torr
Whole column bakeable to 140° C	Eliminates microscope-caused contamination
Double μ-metal shielding of entire column	Minimizes sensitivity to stray AC fields
Completely modular construction	Column can be reconfigured after installation
Self-diagnosing electronics	Rapid remote servicing

Nion UltraSTEM 100 electron microscope

Nion UltraSTEM™ 100

The UltraSTEM™ 100 is a high-performance dedicated scanning-transmission electron microscope (STEM) with many unique features. Its 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. It can also produce high-quality diffraction patterns and even CTEM images.

The UltraSTEM™ has produced atomic-resolution elemental maps in less than a minute (see results). This promises to lead to a new era in electron microscopy in which atomic-resolution elemental maps become a powerful addition to the range of available microscopy techniques. It has also produced unsurpassed images of graphene and similar light-Z materials, while operating at 60 keV, below the knock 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 cartridges
optimized EELS coupling optics
UHV construction
complete remote operability, including sample exchange

Many of these features are unique to the Nion microscope. A full description of the microscope has recently been published in Ultramicroscopy.

Medium angle annular dark field (MAADF) images of the edge of graphene, taken 2 minutes apart. Note the extensive rearrangement that occurred at the edge, and the heavier adatom (probably Al) dangling off the edge. Single arrows in (a) show five-fold C rings, the double arrow shows a single atom of C dangling off the edge. Nion UltraSTEM™ 100, 60 keV. (Krivanek et al., Ultramicroscopy 110 (2010) 935-945)

Nion UltraSTEM™ 100 Condensed specifications

operating energies: typically set up for 100 and 60 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 100 keV): <0.35 eV
AC stray field sensitivity: 1 Å probe motion for 1 mG of

Nion UltraSTEM™ 100 minimum probe sizes

Beam Current:	30 pA	500 pA
100 keV	1.0 Å	1.6 Å
60 keV	1.3 Å	2.5 Å

Nion UltraSTEM™ 200

This electron microscope extends the range of operating voltages of the Nion microscopes to 200 kV. Its column is similar to the UltraSTEM™ 100, but it uses a new, high brightness/high stability cold field emission gun developed by Nion. The higher operating voltage gives:

higher resolution: 0.8 Å high angle dark field resolution (HAADF)
higher probe current: > 1 nA in a 2 Å probe
greater sample penetration

The gun features several new design elements that allow operation at lower voltages at performance levels similar to guns optimized to function only at the lower voltage. The UltraSTEM™ 200 is presently being tested at Nion; the first delivery (to CNRS Orsay) is imminent.

HAADF image of multiply twinned gold crystal particles (800x1200 pixel sub-area of a 2048x2048 image is shown). UltraSTEM200™ operating at 200 kV. Many fine spacings in the particles and well resolved single atoms lying next to the particles can be seen. The insert shows the Fourier transform of the whole image.

Nion UltraSTEM™ 200 condensed specifications*

operating energies: typically set up for 200, 100 and 60 keV
gun brightness: better than 2x109 A/(cm2 sr) at 200 keV
gun vacuum < 4 x10-11 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 polepiece, at 200 keV): Cs = 1.0 mm Cc = 1.2 mm
probe jitter relative to sample: <0.1 Å r.m.s.
HT stability: better than 0.5 ppm/minute
energy resolution in EELS spectra (at 200 keV) <0.35 eV
external enclosure for improved magnetic and acoustic shielding
AC stray field sensitivity: 0.5 Å probe motion for 1 mG of

Nion UltraSTEM™ 200 minimum probe sizes

Beam Current:	30 pA	500 pA
200 keV	0.7 Å	1.0 Å
100 keV	1.0 Å	1.6 Å
60 keV	1.3 Å	2.5 Å

* The UltraSTEM™ is being continuously improved, and the specifications may be subject to change.

Nion 100 kV / 300 kV Cs corrector for VG STEMs

Spherical aberration correctors

For VG HB501, HB601 and HB603 electron microscopes

Nion was the first company in the world to deliver a commercial aberration corrector, for a 100 kV VG HB501. VG microscopes equipped with Nion Cs correctors have established many performance benchmarks by which other microscopes are now measured (see results section). They continue to provide hard-to-equal imaging and analytical performance, at a fraction of the cost of complete new systems.

The correctors are incorporated into the VG microscope at the customer site, without raising the height of the VG column. This is accomplished by replacing the VG scan coils by miniaturized scan coils which fit into the lower bore of the objective lens of the microscope. The corrector then simply occupies the space vacated by the VG scan coils. The corrector consists of four quadrupoles and three octupoles, numerous auxiliary alignment and adjustment coils, and power supplies and controlling software. The corrector is compatible with the UHV standards employed by the VG microscopes: it uses double O-rings with a guard vacuum, and can be baked to 140° C. The controlling software is able to analyze all axial aberrations of the microscope system up to fifth order in a few seconds, and adjusts them automatically for optimum performance.

The VG corrector package includes several major upgrades to the microscope: a bakeable, fiber-optically coupled 1k x 1k CCD camera for Ronchigram recording (for both 100 kV and 300 kV systems), a vacuum upgrade to all-dry construction using ion pumps and a turbo pump, and a quadrupole-octupole EELS coupling module (for 100 kV systems only). A useful further option is a 100 kV OL polepiece that allows standard VG tilt cartridges to be used but lowers the OL aberration coefficients to C_s ~ C_c ~ 1.7 mm.

Custom solutions

Nion is a small and responsive company whose scientists and engineers are deeply knowledgeable about electron microscopes and very interested in pursuing new applications. Our UltraSTEM microscopes are completely modular; all the modules of the microscope column use the same exact mating surface. They can therefore be stacked in almost any sequence and total number. The vacuum system, the electronics, and the detector column are also modular. This means that the column can be reconfigured in many different and unique configurations.

Examples of possible column variants include:

a sample chamber reconfigured for in-situ electrical measurements and other experiments
high-quality post-column optics. A second corrector can be placed after the objective lens to provide C₃/C₅ aberration-corrected CTEM imaging
extra lenses for the post-sample column, to provide high-magnification CTEM imaging even with the objective lens off
extra modules for the illumination column to provide new capabilities such as ultra-fast beam blanking
new detectors, such as large-format CCDs
back-scatter electron detector for imaging of bulk samples
simplified column without an aberration corrector for biological STEM

Nion Service

The service of Nion microscopes is based on four principles:

Remote diagnosis. The Nion microscope is completely remotely operable. If a problem appears, Nion personnel typically diagnose it by operating the microscope remotely, within 24 hours of the problem being reported.
Modularity. Because the microscope is modular, the number of different types of spare parts (PCBs, cables, mechanical modules) is minimized. Nion is typically able to ship a replacement for a defective module that can be installed by the customer within 24 hours of the diagnosis becoming clear.
Site Service. More challenging problems requiring an on-the-spot intervention are typically resolved with a visit by the Nion expert specializing in that particular subsystem. Customers therefore do not have to go through several visits by service engineers who are not sufficiently familiar with the full complexities of the microscope and end up passing the problem onto a higher level in the service organization.
Update visits. As a part of the Nion service plan, Nion engineers visit the site at least once a year to carry out major software updates and customer training refreshers.