Manufacturing Bits: Sept. 11

Microscopy resolution record; X-ray microscopes.


Microscopy resolution record
Cornell University says that it has achieved a world’s record for the highest resolution microscope.

Using a scanning transmission electron microscope (STEM) and a new detector, Cornell has demonstrated features of atoms in a two-dimensional semiconductor sheet as small as 0.39 angstroms. In comparison, atoms are about 2 to 4 angstroms in diameter. An angstrom is 0.1nm.

Electron microscopy is widely used in the industry. It is used to measure and characterize materials. Generally, though, the resolution limit for samples is about an angstrom, according to Cornell and the U.S. Department of Energy.

To go beyond that limit, Cornell decided to image a 2D material called molybdenum disulfide. Then, to measure the sample, researchers used a STEM and a new pixel array detector, dubbed EMPAD. The EMPAD consists of a 128×128 array of electron-sensitive pixels. Each one is 150 microns.

The EMPAD was retrofitted on the STEM. With these technologies, researchers utilized a metrology technique called ptychography or scanning diffraction microscopy. This makes use of a beam of coherent radiation. The beam illuminates a sample of material. Then, the information from the beam analyzes the diffraction patterns.

Using a beam energy of 80keV in the STEM, researchers from Cornell generated images of electrons through a molybdenum disulfide sample. This, in turn, produced two-dimensional diffraction patterns. Using computer algorithms with indirect scattering data, Cornell produced the image.

This method could enable a way to obtain images of the bonds between a single atom. “The analogy I like to use is, a car is coming at you at night,” said Sol Gruner, a professor of physics at Cornell. “And you’re looking at the lights coming at you, and you’re able to read the license plate between them without being blinded.”

A ptychographic image of two sheets of molybdenum disulfide, with one rotated by 6.8 degrees with respect to the other. The distances between individual atoms range from a full atomic bond length down to complete overlap. (Source: Cornell)

X-ray microscope lens
The Max Planck Institute for Intelligent Systems has developed a new polymer lens technology for X-ray microscopes.

X-ray microscopes are used in many applications, such as exploring buried features in materials at high resolutions. But X-ray scopes require expensive optics at nanoscale geometries.

In response, researchers from Max Planck developed a new method for making three-dimensional kinoforms. A kinoform is a converging lens that can focus X-ray radiation. For this, researchers used a 3D-nanoprinted technique to deposit materials on the kinoform. Beryllium and diamond are often used as the materials in this application, but they each have some drawbacks.

Instead, researchers used a two-photon polymerization (2PP) polymers to fabricate the kinoforms or X-ray lenses. The materials have good X-ray optical properties. “Selecting the right materials is a crucial part of the manufacturing process” said Kahraman Keskinbora from the Max Planck Institute. “We realized that the 2PP-polymers come with extremely favorable X-ray optical properties that could only be matched by beryllium – a highly toxic element – and diamond, which is very expensive.

“By integrating various optics, we can effectively control and manipulate the X-ray wavefront. With several lenses and other wavefront shaping elements positioned one after the other, we can optimize these integrated X-ray optics for even the very hard X-ray energy range,” Keskinbora said. “So, there are a lot of new research venues to follow.”

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