Rice University, renowned for nanoscale science, has installed microscopes that will allow researchers to peer deeper than ever into the fabric of the universe.
The Titan Themis scanning/transmission electron microscope, one of the most powerful in the United States, will enable scientists from Rice as well as academic and industrial partners to view and analyze materials smaller than a nanometer — a billionth of a meter — with startling clarity.
The microscope has the ability to take images of materials at angstrom-scale (one-tenth of a nanometer) resolution, about the size of a single hydrogen atom.
Images will be captured with a variety of detectors, including X-ray, optical and multiple electron detectors and a 4K-resolution camera, equivalent to the number of pixels in the most modern high-resolution televisions. The microscope gives researchers the ability to create three-dimensional structural reconstructions and carry out electric field mapping of subnanoscale materials.
“Seeing single atoms is exciting, of course, and it’s beautiful,” said Emilie Ringe, a Rice assistant professor of materials science and nanoengineering and of chemistry. “But scientists saw single atoms in the ’90s, and even before. Now, the real breakthrough is that we can identify the composition of those atoms, and do it easily and reliably.” Ringe’s research group will operate the Titan Themis and a companion microscope that will image larger samples.
Electron microscopes use beams of electrons rather than rays of light to illuminate objects of interest. Because the wavelength of electrons is so much smaller than that of photons, the microscopes are able to capture images of much smaller things with greater detail than even the highest-resolution optical microscope.
“The beauty of these newer instruments is their analytical capabilities,” Ringe said. “Before, in order to see single atoms, we had to work a machine for an entire day and get it just right and then take a picture and hold our breath. These days, seeing atoms is routine.
“And now we can probe a particular atom’s chemical composition. Through various techniques, either via scattering intensity, X-rays emission or electron-beam absorption, we can figure out, say, that we’re looking at a palladium atom or a carbon atom. We couldn’t do that before.”
Ringe said when an electron beam ejects a bound electron from a target atom, it creates an empty site. “That can be filled by another electron within the atom, and the energy difference between this electron and the missing electron is emitted as an X-ray,” she said. “That X-ray is like a fingerprint, which we can read. Different types of atoms have different energies.”
She said the incident electron beam loses a bit of energy when it knocks an atom’s electron loose, and that energy loss can also be measured with a spectroscope to identify the atom. The X-ray and electron techniques are independent but complementary. “Typically, you use either/or, and it depends on what element you’re looking at,” Ringe said.
This story is reprinted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.