Products
MAG*I*CAL
MAG*I*CAL®
Traceable Transmission Electron Microscopy Calibration Standard
The MAG*I*CAL performs all major TEM calibrations:
- All TEM magnification ranges
- Camera constant
- Image Diffraction Pattern Rotation
- Directly traceable to a natural constant
MAG*I*CAL® is the world’s smallest ruler and have been inducted into the Guinness Book of World Records.
In the diagrams of the MAG*I*CAL® grid located above, the arrows point to the four regions containing the calibration marks.
MAGNIFICATION CALIBRATION STANDARD FOR TEM
MAG*I*CAL™ consists of an ion milled cross section of a silicon single crystal consisting of a series of atomically flat layers of Si and SiGe, which have been grown epitaxially by MBE (molecular beam epitaxy).
When the calibration structure is viewed in a TEM, it appears as a series of light and dark layers where the layer thicknesses are accurately known.
The calibra- ted thickness measurements of these light (silicon) and dark (SiGe) layers are based on careful TEM measurements of the <111> lattice spacing of silicon, which is visible on the calibration sample itself, and are supported by x-ray diffraction measurements.
The layer spacing are designed so that the sample can be used to calibrate the entire magnification range in a TEM, from 1,000X to 1,000,000X. As the sample is also a single crystal of silicon, the calibrations requiringelectron diffraction information such as the
came- ra constant and image/diffraction patternrotation can also be performed easily andunambiguously.
One single calibration sample can therefore be used to provide all three of the major TEM instrument calibra- tion at all magnifications and all camera lengths.
To improve accuracy when making measurements, always measure the largest distance clearly visible on the micrograph.
For example, at the highest magnification ranges, measure the distance across the entire set of five dark layers and four light layers, instead of trying to measure an individual dark layer.
Aligning the Reference Standard
The MAG*I*CAL ™ Calibration Standard is made from a single crystal of silicon, and therefore has many very useful attributes as a TEM standard.
To take advantage of these attributes, mount the standard in the TEM sample holder with the epoxy line of the standard parallel to the stem of the TEM sample holder (see Fig.2, next page).
Translate the standard to bring into view the calibration marks close to the thin edge near the perforation in the center of the sample (arrows, Fig. 2), and focus. Put the TEM into diffraction mode, choose the smallest camera length, and adjust the intensity control (condenser control) back and forth to find the proper value of over-focus that forms the striking pattern called a Kikuchi pattern, similar to Fig. 1 below, but perhaps rotated.
These Kikuchi bands are formed by elastic Bragg scattering of previously inelastically scattered electrons. The intensity control can be adjusted so that either a diffraction spot pattern or a Kikuchi pattern can be observed.
The standard should be tilted to move the Kikuchi pattern so that the central “intersection” in this diagram (where the largest number of bands intersect) is centered on the brightest (zero order) diffraction spot in the electron diffraction pattern (adjust the intensity control back and forth).
It may be necessary to translate the standard to slightly thicker or thinner regions to get a clear Kikuchi pattern.
Kikuchi pattern of single crystal silicon viewed down the <011> zone axis. The broad horizontal band in the center of this figure is between the {200} Kikuchi lines.
TEM micrograph of the MAG*I*CAL®. Inset shows a higher magnification image of one of the layered structures
Diagram of the MAG*I*CAL® grid. The arrows point to the four regions containing the calibration marks.
A Kikuchi pattern from the single crystal sample which can be used to align the sample.
An optical micrograph of the colors of silicon when it is thinned down to TEM thicknesses, the 1mm central perforation, and the four areas containing the calibration markings (arrows).
A lattice image of the single crystal silicon sample. The silicon <1 1 1> lattice planes should be measured perpendicular to the planes, in the direction of the arrow.
| Art. | Description | Unit | Price | Quantity | |
|---|---|---|---|---|---|
| AGS1936 | MAG*I*CAL Calibration Standard |
Each | p.o.r. |
