New electron microscopes will capture images at subnanometer resolution

 

Tue, 06/30/2015 - 10:15am Rice University The Titan Themis microscope at Rice University incorporates a variety of detectors, including X-ray, optical and multiple electron detectors and a 4K-resolution camera. The microscope gives researchers the ability to create three-dimensional structural reconstructions and carry out electric field mapping of subnanoscale materials. Courtesy of Jeff Fitlow/Rice UniversityHOUSTON — Rice University 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. The second instrument, a Helios NanoLab 600 DualBeam microscope, will be used for three-dimensional imaging, analysis of larger samples and preparation of thin slices of samples for the more powerful Titan next door. Both tools reside in the university’s Brockman Hall for Physics, which opened in 2011 and features sophisticated vibration-dampening capabilities. The microscopes require the best possible isolation from vibration, electric fields and acoustic noise to produce the best images, Ringe said. “We have wanted a high-end microscopy facility at Rice because so many of us are working on nanomaterials,” said Pulickel Ajayan, a professor and founding chair of Rice’s Department of Materials Science and NanoEngineering. “This has been an issue because in order to be competitive you have to have the best atomic-scale characterization techniques. This will put us in business in terms of imaging and understanding new materials.” He said the facility will position Rice as one of the most competitive institutions to recruit students and faculty, attract grants and publish groundbreaking results. “A visual image of something on an atomic level can give you so much more information than a few numbers can,” said Peter Rossky, a theoretical chemist and dean of Rice’s Wiess School of Natural Sciences. Comparing images of the same material taken by an older electron microscope and the Titan Themis was like “the difference between a black-and-white TV and high-definition color,” he said. Ringe said Rice’s Titan is a fourth-generation model manufactured in the Netherlands. It’s the latest and most powerful model and the first to be installed in the United States. “Taking a complex image — not just a picture but a spectrum image that has lots of energy information — in the older model would take about 35 minutes,” she said. “By that time, the electron beam has destroyed whatever you were trying to look at. “With this generation, you have the data you need in about two minutes. You can generate a lot more data more quickly. It’s not just better; it’s enabling.” Edwin Thomas, the William and Stephanie Sick Dean of Rice’s George R. Brown School of Engineering, expects the new instruments to ignite the already strong research culture at the university. “This is going to influence the kind of people who will be attracted to apply to and then come to Rice,” said Thomas, a materials scientist. “I’m sure there will be people on campus who, once they find out the capabilities, are going to shift their compasses and take advantage of these machines. The whole point is to have an impact on science and society.” Rice plans to host a two-day workshop in September to introduce the microscopes and their capabilities to the research community at the university and beyond. Beginning this summer, Ringe said, the electron microscopy center will be open to Rice students and faculty as well as researchers from other universities and industry. Ringe looks forward to bringing researchers into the new microscopy lab — and to the research that will emerge. “I hope everyone’s going to come out with a blockbuster paper with images from these instruments,” she said. “I would like every paper from Rice to have fantastic, crystal-clear, atomic-resolution images and the best possible characterization.”   SOURCE: Rice University