Manufacturing Bits: Dec. 15

Ghost imaging quantum microscopes
The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory has begun building a quantum-enhanced X-ray microscope based on a technology called ghost imaging.

Still in R&D, quantum X-ray microscopes promise to provide higher resolution images with less damage to a sample.

Using the National Synchrotron Light Source II (NSLS-II), researchers from Brookhaven use traditional X-ray metrology techniques to study the structural, chemical, and electronic makeup of materials at the atomic scale. NSLS-II is a large electron storage ring facility, which offers researchers an array of beamlines with X-ray, ultraviolet, and infrared light capabilities.

Conventional X-ray metrology techniques enable high resolutions, but this powerful light source can also damage certain samples. Low-dose X-ray technology can prevent the damage of a sample, but the imaging resolution is reduced.

That’s where quantum X-ray microscopes fit in. Using the quantum properties of X-rays, researchers will be able to image more sensitive biomolecules and other technologies without sacrificing resolution

Researchers are developing a quantum-enhanced X-ray microscope using an experimental technique called ghost imaging. The system will be complete upon demonstrating ghost imaging of objects with resolution below 10nm. The technology is targeted for 2023.

“Compared to typical X-ray imaging techniques, which send a single beam of photons (particles of light) through a sample and onto a detector, ghost imaging requires the X-ray beam be split into two streams of entangled photons—only one of which passes through the sample, but both gather information,” according to Brookhaven.

“One stream goes through the sample and is collected by a detector that records the photons with good time resolution, while the other stream of photons encodes the exact direction in which the photons propagate,” said Andrei Fluerasu, lead beamline scientist at NSLS-II’s Coherent Hard X-ray Scattering (CHX) beamline, where the microscope will be developed. “It sounds like magic. But with mathematical calculations, we’ll be able to correlate the information from the two beams.”

“If we are successful in building a quantum-enhanced X-ray microscope, we will be able to image biomolecules with very high resolution and a very low dose of X-rays,” said Sean McSweeney, manager of the structural biology program at NSLS-II.

X-ray microscopy record
Friedrich–Alexander University Erlangen–Nürnberg (FAU), Paul Scherrer Institute (PSI) and others have set a new image resolution record in X-ray microscopy.

Researchers have achieved spatial resolution in the single-digit nanometer scale. More specifically, using soft X-ray microscopy, they achieved an image resolution of 7nm.

For years, X-ray microscopy and spectroscopy have been used to explore various technologies at high resolutions. X-ray metrology techniques are used to study biological specimens, materials, matter and other technologies.

Over the years, the industry has used X-ray metrology techniques in order to obtain sizes below 10nm using mirrors, Fresnel zone plate lenses, and multi-layer lenses, according to researchers in Optica, a technology journal.

“In addition, other methods based on image reconstruction have reached imaging resolution well below 10nm,” said Benedikt Rösner, a researcher from PSI in Optica. “However, direct imaging at with better resolution remained difficult so far, due to the finesse of the overall instrument being limited by positioning precision and stability.”

To enable sub-10nm resolutions, researchers from FAU and PSI used soft X-ray microscopy techniques. This technology uses low-energy X-rays to study the properties of materials in the nanoscale

Researchers have demonstrated sub-10nm microscopic resolutions using two scanning X-ray transmission microscopes at the PolLux and HERMES beamlines at the Swiss Light Source and Synchrotron Soleil, respectively.

In operation, an X-ray beam is focused onto the specimen, which is raster-scanned at high precision. Fresnel zone plates are most commonly used as diffractive focusing elements in X-ray microscopy.

Using the technology, researchers studied the magnetic field orientation of iron particles measuring 5nm to 20nm. The technology can also be used to probe elemental, electronic, magnetic or chemical variations.

“For dynamic processes such as chemical reactions or magnetic particle interaction, we need to be able to view the structures directly,” said Rainer Fink, a professor at FAU. “X-ray microscopy is especially suitable for this as it can be used more flexibly in magnetic environments than electron microscopy, for example.

“We optimized the structure size of the Fresnel zone plates which are used to focus X-rays. In addition, we were able to position the samples in the device at a much higher accuracy and reproduce this accuracy,” Fink said. “We assume that our results will push forward research into energy materials and nanomagnetism in particular. The relevant structure sizes in this fields are often below current resolution limits.”