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Center for Functional Nanomaterials

Daejeon, South Korea

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News Article | May 10, 2017
Site: www.greencarcongress.com

« Praj cellulosic ethanol demo plant running in India; commercial projects coming | Main | Energy companies partner with RMI and Grid Singularity to launch global blockchain initiative for energy » Chemists from the US Department of Energy’s Brookhaven National Laboratory and their collaborators have definitively identified the active sites of a catalyst commonly used for making methanol from CO . The results, published in the journal Science, resolve a longstanding debate about exactly which catalytic components take part in the chemical reactions—and thus which should be the focus of efforts to boost performance. The hydrogenation of carbon dioxide is a key step in the production of methanol; catalysts made from copper (Cu) and zinc oxide (ZnO) on alumina supports are often used. There has been a debate over the actual active sites for the reaction on the catalyst. Different groups of scientists had proposed two different active sites for the catalyst—a portion of the system with just copper and zinc atoms, or a portion with copper zinc oxide. To determine which part of the molecular structure binds and breaks and makes bonds to convert reactants to product—and how it does that—co-author Jose Rodriguez performed a series of laboratory experiments using well-defined model catalysts, including one made of zinc nanoparticles supported on a copper surface, and another with zinc oxide nanoparticles on copper. To tell the two apart, he used an energetic x-ray beam to zap the samples, and measured the properties of electrons emitted. These electronic “signatures” contain information about the oxidation state of the atoms the electrons came from—whether zinc or zinc oxide. Meanwhile Liu, Jingguang Chen of Brookhaven Lab and Columbia University, and Shyam Kattel, the first author of the paper and a postdoctoral fellow co-advised by Liu and Chen, used computational resources at Brookhaven’s Center for Functional Nanomaterials (CFN) and the National Energy Research Scientific Computing Center (NERSC)—two DOE Office of Science User Facilities—to model how these two types of catalysts would engage in the CO -to-methanol transformations. These theoretical studies use calculations that take into account the basic principles of breaking and making chemical bonds, including the energy required, the electronic states of the atoms, and the reaction conditions, allowing scientists to derive the reaction rates and determine which catalyst will give the best rate of conversion. Those predictions matched what Rodriguez observed in the laboratory. All the sites participating in these reactions were copper zinc oxide. Optimizing the copper/zinc oxide interface will become the driving principal for designing a new catalyst, the scientists say. Rodriguez said that the team will try different configurations of the atoms at the copper/zinc oxide interface to see how that affects the reaction rate. Additionally, they will move from studying the model system to systems that would be more practical for use by industry. An essential tool for this next step will be Brookhaven’s National Synchrotron Light Source II (NSLS-II), another Office of Science User Facility. NSLS-II produces extremely bright beams of x-rays—about 10,000 times brighter than the broad-beam laboratory x-ray source used in this study. Those intense x-ray beams will allow the scientists to take high-resolution snapshots that reveal both structural and chemical information about the catalyst, the reactants, and the chemical intermediates that form as the reaction occurs. An additional co-author, Pedro Ramírez of Universidad Central de Venezuela, made important contributions to this study by helping to test the activity of the copper zinc and copper zinc oxide catalysts. This research was supported by the DOE Office of Science.


News Article | May 16, 2017
Site: www.materialstoday.com

The ability to pattern materials at ever-smaller sizes – using electron-beam lithography (EBL), in which an electron-sensitive material is exposed to a focused beam of electrons, as a primary method – is driving advances in nanotechnology. When the feature size of materials is reduced from the macroscale to the nanoscale, individual atoms and molecules can be manipulated to alter material properties, such as color, chemical reactivity, electrical conductivity and light interactions. In the ongoing quest to pattern materials with ever-smaller feature sizes, scientists at the Center for Functional Nanomaterials (CFN) – a US Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory – have recently set a new record. Performing EBL with a scanning transmission electron microscope (STEM), they have patterned thin films of the polymer poly(methyl methacrylate) (PMMA) with individual features as small as 1nm, and with a spacing between features of just 11nm. As the scientists report in a paper in Nano Letters, this has allowed them to fabricate nearly one trillion features per square centimeter. "Our goal at CFN is to study how the optical, electrical, thermal and other properties of materials change as their feature sizes get smaller," said lead author Vitor Manfrinato, a research associate in CFN's electron microscopy group who began the project as a CFN user while completing his doctoral work at Massachusetts Institute of Technology. "Until now, patterning materials at a single nanometer has not been possible in a controllable and efficient way." Commercial EBL instruments typically pattern materials at sizes of 10–20nm. Techniques that can produce higher-resolution patterns require special conditions that either limit their practical utility or dramatically slow down the patterning process. Here, the scientists pushed the resolution limits of EBL by installing a pattern generator – an electronic system that precisely moves the electron beam over a sample to draw patterns designed with computer software – in one of CFN's aberration-corrected STEMs, a specialized microscope that provides a focused electron beam at the atomic scale. "We converted an imaging tool into a drawing tool that is capable of not only taking atomic-resolution images but also making atomic-resolution structures," said co-author Aaron Stein, a senior scientist in the electronic nanomaterials group at CFN. Their measurements with this instrument show a nearly 200% reduction in feature size (from 5nm to 1.7nm) and a 100% increase in areal pattern density (from 0.4 trillion to 0.8 trillion dots per square centimeter, reducing the spacing between features from 16nm to 11nm) over previous scientific reports. The team's patterned PMMA films can be used as stencils for transferring the drawn single-digit nanometer feature into any other material. In this work, the scientists created structures smaller than 5nm in both metallic (gold palladium) and semiconducting (zinc oxide) materials. Their fabricated gold palladium features were as small as six atoms wide. Despite this record-setting demonstration, the team remains interested in understanding the factors that still limit resolution, and ultimately pushing EBL to its fundamental limit. "The resolution of EBL can be impacted by many parameters, including instrument limitations, interactions between the electron beam and the polymer material, molecular dimensions associated with the polymer structure and chemical processes of lithography," explained Manfrinato. An exciting result of this study was the realization that polymer films can be patterned at sizes much smaller than the 26nm effective radius of the PMMA macromolecule. "The polymer chains that make up a PMMA macromolecule are a million repeating monomers (molecules) long – in a film, these macromolecules are all entangled and balled up," said Stein. "We were surprised to find that the smallest size we could pattern is well below the size of the macromolecule and nears the size of one of the monomer repeating units, as small as a single nanometer." Next, the team plans to use their technique to study the properties of materials patterned at 1nm dimensions. One early target will be the semiconducting material silicon, whose electronic and optical properties are predicted to change at the single-digit nanometer scale. "This technique opens up many exciting materials engineering possibilities, tailoring properties if not atom by atom, then closer than ever before," said Stein. "Because the CFN is a national user facility, we will soon be offering our first-of-a-kind nanoscience tool to users from around the world. It will be really interesting to see how other scientists make use of this new capability." This story is adapted from material from Brookhaven National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


Determining how the ions of the liquid move and rearrange in response to an applied voltage on electrodes is key to optimizing the performance of ionic liquids for energy storage devices UPTON, NY--Ionic liquids--salts made by combining positively charged molecules (cations) and negatively charged molecules (anions) that are liquid at relatively low temperatures, often below room temperature--are increasingly being investigated for uses in batteries, supercapacitors, and transistors. Their unique physical and chemical properties, including good ionic conductivity, low flammability and volatility, and high thermal stability, make them well suited for such applications. But thousands of ionic liquids exist and exactly how they interact with the electrified surfaces of electrodes remains poorly understood, making it difficult to choose the proper ionic liquid for a particular application. Now, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have demonstrated a new method for observing in real time how the ions of such liquids move and reconfigure as different voltages are applied to the electrodes. The method is described in a paper published on May 12 in the online edition of Advanced Materials. "When ionic liquid electrolytes come into contact with an electrified electrode, a special structure consisting of alternating layers of cations and anions--called an electric double layer (EDL)--forms at that interface," said first author Wattaka Sitaputra, a scientist at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility where the research was conducted. "But tracking the real-time evolution of the EDL, where the electrochemical reactions take place in batteries, is difficult because it is very thin (only a few nanometers thick) and buried by the bulk portion of the ionic liquid." Until now, scientists have only been able to look at the initial and final EDL structures by using microscopy and spectroscopy techniques; the intermediate structure has been harder to probe. To visualize the structural changes of the EDL and the movement of ions as voltage is applied to the electrodes, the Brookhaven team used an imaging technique called photoemission electron microscopy (PEEM). In this technique, surface electrons are excited with an energy source and accelerated into an electron microscope, where they pass through magnifying lenses before being projected onto a detector that records the electrons emitted from the surface. Local variations in the photoemission signal intensities are then used to generate contrast images of the surface. In this case, the team used ultraviolet light to excite the electrons on the surfaces of both the ionic liquid (known as EMMIM TFSI) they deposited as thin films and two gold electrodes they fabricated. "Imaging the whole surface, including the electrodes and the space between them, allows us to study not only the evolution of the structure of the ionic liquid-electrode interface but also to probe both electrodes at the same time while changing various conditions of the system," said CFN scientist and coauthor Jerzy (Jurek) Sadowski. In this initial demonstration, the team changed the voltage applied to the electrodes, the thickness of the ionic liquid films, and the temperature of the system, all while monitoring changes in photoemission intensity. The scientists found that the ions (which normally layer in a checkerboard-like configuration for this ionic liquid) move and arrange themselves according to the sign and magnitude of the applied voltage. Cations gravitate toward the electrode with the negative bias to counter the charge, and vice versa for anions. As the difference in potential increases between the two electrodes, a highly dense layer of cations or anions can accumulate near the biased electrode, preventing further ions of the same charge from moving there (a phenomenon called overcrowding) and reducing ion mobility. They also discovered that more counter ions gather near the biased electrode in thicker films. "For very thin films, the number of ions available for rearrangement is small so the EDL layer may not be able to form," said Sitaputra. "In the thicker films, more ions are available and they have more room to move around. They rush to the interface and then disperse back into the bulk upon overcrowding to form a more stable structure." The team further explored the importance of mobility in the rearrangement process by cooling the thicker film until the ions virtually stopped moving. According to the team, applying PEEM to an operando experiment is quite novel and has never been done for ionic liquids. "We had to overcome several technical challenges in the experimental setup, including designing and fabricating the gold-patterned electrodes and incorporating the sample holder in the electron microscope," explained Sadowski. "Ionic liquids probably have not been investigated through this technique because putting a liquid into an ultrahigh vacuum-based microscope seems counterintuitive." The team plans to continue their research using the new aberration-corrected low-energy electron microscope (LEEM)/PEEM system--installed through a partnership between CFN and the National Synchrotron Light Source II (NSLS-II), another DOE Office of Science User Facility at Brookhaven--at NSLS-II's Electron Spectro-Microscopy beamline. This system will enable the team to study not only the structural and electronic changes but also the chemical changes of the ionic liquid-electrode interface--all in a single experiment. By determining these unique properties, scientists will be able to select the optimal ionic liquids for specific energy storage applications. This work was supported in part by the DOE's Laboratory Directed Research and Development program and represents a collaboration between the CFN and Brookhaven's Chemistry and Sustainable Energy Technologies Divisions. Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.


News Article | May 16, 2017
Site: www.sciencedaily.com

Ionic liquids -- salts made by combining positively charged molecules (cations) and negatively charged molecules (anions) that are liquid at relatively low temperatures, often below room temperature -- are increasingly being investigated for uses in batteries, supercapacitors, and transistors. Their unique physical and chemical properties, including good ionic conductivity, low flammability and volatility, and high thermal stability, make them well suited for such applications. But thousands of ionic liquids exist and exactly how they interact with the electrified surfaces of electrodes remains poorly understood, making it difficult to choose the proper ionic liquid for a particular application. Now, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have demonstrated a new method for observing in real time how the ions of such liquids move and reconfigure as different voltages are applied to the electrodes. The method is described in a paper published on May 12 in the online edition of Advanced Materials. "When ionic liquid electrolytes come into contact with an electrified electrode, a special structure consisting of alternating layers of cations and anions -- called an electric double layer (EDL) -- forms at that interface," said first author Wattaka Sitaputra, a scientist at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility where the research was conducted. "But tracking the real-time evolution of the EDL, where the electrochemical reactions take place in batteries, is difficult because it is very thin (only a few nanometers thick) and buried by the bulk portion of the ionic liquid." Until now, scientists have only been able to look at the initial and final EDL structures by using microscopy and spectroscopy techniques; the intermediate structure has been harder to probe. To visualize the structural changes of the EDL and the movement of ions as voltage is applied to the electrodes, the Brookhaven team used an imaging technique called photoemission electron microscopy (PEEM). In this technique, surface electrons are excited with an energy source and accelerated into an electron microscope, where they pass through magnifying lenses before being projected onto a detector that records the electrons emitted from the surface. Local variations in the photoemission signal intensities are then used to generate contrast images of the surface. In this case, the team used ultraviolet light to excite the electrons on the surfaces of both the ionic liquid (known as EMMIM TFSI) they deposited as thin films and two gold electrodes they fabricated. "Imaging the whole surface, including the electrodes and the space between them, allows us to study not only the evolution of the structure of the ionic liquid-electrode interface but also to probe both electrodes at the same time while changing various conditions of the system," said CFN scientist and coauthor Jerzy (Jurek) Sadowski. In this initial demonstration, the team changed the voltage applied to the electrodes, the thickness of the ionic liquid films, and the temperature of the system, all while monitoring changes in photoemission intensity. The scientists found that the ions (which normally layer in a checkerboard-like configuration for this ionic liquid) move and arrange themselves according to the sign and magnitude of the applied voltage. Cations gravitate toward the electrode with the negative bias to counter the charge, and vice versa for anions. As the difference in potential increases between the two electrodes, a highly dense layer of cations or anions can accumulate near the biased electrode, preventing further ions of the same charge from moving there (a phenomenon called overcrowding) and reducing ion mobility. They also discovered that more counter ions gather near the biased electrode in thicker films. "For very thin films, the number of ions available for rearrangement is small so the EDL layer may not be able to form," said Sitaputra. "In the thicker films, more ions are available and they have more room to move around. They rush to the interface and then disperse back into the bulk upon overcrowding to form a more stable structure." The team further explored the importance of mobility in the rearrangement process by cooling the thicker film until the ions virtually stopped moving. According to the team, applying PEEM to an operando experiment is quite novel and has never been done for ionic liquids. "We had to overcome several technical challenges in the experimental setup, including designing and fabricating the gold-patterned electrodes and incorporating the sample holder in the electron microscope," explained Sadowski. "Ionic liquids probably have not been investigated through this technique because putting a liquid into an ultrahigh vacuum-based microscope seems counterintuitive." The team plans to continue their research using the new aberration-corrected low-energy electron microscope (LEEM)/PEEM system -- installed through a partnership between CFN and the National Synchrotron Light Source II (NSLS-II), another DOE Office of Science User Facility at Brookhaven -- at NSLS-II's Electron Spectro-Microscopy beamline. This system will enable the team to study not only the structural and electronic changes but also the chemical changes of the ionic liquid-electrode interface -- all in a single experiment. By determining these unique properties, scientists will be able to select the optimal ionic liquids for specific energy storage applications.


Now, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have demonstrated a new method for observing in real time how the ions of such liquids move and reconfigure as different voltages are applied to the electrodes. The method is described in a paper published on May 12 in the online edition of Advanced Materials. "When ionic liquid electrolytes come into contact with an electrified electrode, a special structure consisting of alternating layers of cations and anions—called an electric double layer (EDL)—forms at that interface," said first author Wattaka Sitaputra, a scientist at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility where the research was conducted. "But tracking the real-time evolution of the EDL, where the electrochemical reactions take place in batteries, is difficult because it is very thin (only a few nanometers thick) and buried by the bulk portion of the ionic liquid." Until now, scientists have only been able to look at the initial and final EDL structures by using microscopy and spectroscopy techniques; the intermediate structure has been harder to probe. To visualize the structural changes of the EDL and the movement of ions as voltage is applied to the electrodes, the Brookhaven team used an imaging technique called photoemission electron microscopy (PEEM). In this technique, surface electrons are excited with an energy source and accelerated into an electron microscope, where they pass through magnifying lenses before being projected onto a detector that records the electrons emitted from the surface. Local variations in the photoemission signal intensities are then used to generate contrast images of the surface. In this case, the team used ultraviolet light to excite the electrons on the surfaces of both the ionic liquid (known as EMMIM TFSI) they deposited as thin films and two gold electrodes they fabricated. "Imaging the whole surface, including the electrodes and the space between them, allows us to study not only the evolution of the structure of the ionic liquid-electrode interface but also to probe both electrodes at the same time while changing various conditions of the system," said CFN scientist and coauthor Jerzy (Jurek) Sadowski. In this initial demonstration, the team changed the voltage applied to the electrodes, the thickness of the ionic liquid films, and the temperature of the system, all while monitoring changes in photoemission intensity. The scientists found that the ions (which normally layer in a checkerboard-like configuration for this ionic liquid) move and arrange themselves according to the sign and magnitude of the applied voltage. Cations gravitate toward the electrode with the negative bias to counter the charge, and vice versa for anions. As the difference in potential increases between the two electrodes, a highly dense layer of cations or anions can accumulate near the biased electrode, preventing further ions of the same charge from moving there (a phenomenon called overcrowding) and reducing ion mobility. They also discovered that more counter ions gather near the biased electrode in thicker films. "For very thin films, the number of ions available for rearrangement is small so the EDL layer may not be able to form," said Sitaputra. "In the thicker films, more ions are available and they have more room to move around. They rush to the interface and then disperse back into the bulk upon overcrowding to form a more stable structure." The team further explored the importance of mobility in the rearrangement process by cooling the thicker film until the ions virtually stopped moving. According to the team, applying PEEM to an operando experiment is quite novel and has never been done for ionic liquids. "We had to overcome several technical challenges in the experimental setup, including designing and fabricating the gold-patterned electrodes and incorporating the sample holder in the electron microscope," explained Sadowski. "Ionic liquids probably have not been investigated through this technique because putting a liquid into an ultrahigh vacuum-based microscope seems counterintuitive." The team plans to continue their research using the new aberration-corrected low-energy electron microscope (LEEM)/PEEM system—installed through a partnership between CFN and the National Synchrotron Light Source II (NSLS-II), another DOE Office of Science User Facility at Brookhaven—at NSLS-II's Electron Spectro-Microscopy beamline. This system will enable the team to study not only the structural and electronic changes but also the chemical changes of the ionic liquid-electrode interface—all in a single experiment. By determining these unique properties, scientists will be able to select the optimal ionic liquids for specific energy storage applications. Explore further: Ioliomics as an emerging research discipline More information: Wattaka Sitaputra et al, In Situ Probing of Ion Ordering at an Electrified Ionic Liquid/Au Interface, Advanced Materials (2017). DOI: 10.1002/adma.201606357


Ionic liquids—salts made by combining positively charged molecules (cations) and negatively charged molecules (anions) that are liquid at relatively low temperatures, often below room temperature—are increasingly being investigated for uses in batteries, supercapacitors, and transistors. Their unique physical and chemical properties, including good ionic conductivity, low flammability and volatility, and high thermal stability, make them well suited for such applications. But thousands of ionic liquids exist and exactly how they interact with the electrified surfaces of electrodes remains poorly understood, making it difficult to choose the proper ionic liquid for a particular application. Now, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have demonstrated a new method for observing in real time how the ions of such liquids move and reconfigure as different voltages are applied to the electrodes. The method is described in a paper published on May 12 in the online edition of Advanced Materials. “When ionic liquid electrolytes come into contact with an electrified electrode, a special structure consisting of alternating layers of cations and anions—called an electric double layer (EDL)—forms at that interface,” said first author Wattaka Sitaputra, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility where the research was conducted. “But tracking the real-time evolution of the EDL, where the electrochemical reactions take place in batteries, is difficult because it is very thin (only a few nanometers thick) and buried by the bulk portion of the ionic liquid.” Until now, scientists have only been able to look at the initial and final EDL structures by using microscopy and spectroscopy techniques; the intermediate structure has been harder to probe. To visualize the structural changes of the EDL and the movement of ions as voltage is applied to the electrodes, the Brookhaven team used an imaging technique called photoemission electron microscopy (PEEM). In this technique, surface electrons are excited with an energy source and accelerated into an electron microscope, where they pass through magnifying lenses before being projected onto a detector that records the electrons emitted from the surface. Local variations in the photoemission signal intensities are then used to generate contrast images of the surface. In this case, the team used ultraviolet light to excite the electrons on the surfaces of both the ionic liquid (known as EMMIM TFSI) they deposited as thin films and two gold electrodes they fabricated. “Imaging the whole surface, including the electrodes and the space between them, allows us to study not only the evolution of the structure of the ionic liquid–electrode interface but also to probe both electrodes at the same time while changing various conditions of the system,” said CFN scientist and coauthor Jerzy (Jurek) Sadowski. In this initial demonstration, the team changed the voltage applied to the electrodes, the thickness of the ionic liquid films, and the temperature of the system, all while monitoring changes in photoemission intensity. The scientists found that the ions (which normally layer in a checkerboard-like configuration for this ionic liquid) move and arrange themselves according to the sign and magnitude of the applied voltage. Cations gravitate toward the electrode with the negative bias to counter the charge, and vice versa for anions. As the difference in potential increases between the two electrodes, a highly dense layer of cations or anions can accumulate near the biased electrode, preventing further ions of the same charge from moving there (a phenomenon called overcrowding) and reducing ion mobility. They also discovered that more counter ions gather near the biased electrode in thicker films. “For very thin films, the number of ions available for rearrangement is small so the EDL layer may not be able to form,” said Sitaputra. “In the thicker films, more ions are available and they have more room to move around. They rush to the interface and then disperse back into the bulk upon overcrowding to form a more stable structure.” The team further explored the importance of mobility in the rearrangement process by cooling the thicker film until the ions virtually stopped moving. According to the team, applying PEEM to an operando experiment is quite novel and has never been done for ionic liquids. “We had to overcome several technical challenges in the experimental setup, including designing and fabricating the gold-patterned electrodes and incorporating the sample holder in the electron microscope,” explained Sadowski. “Ionic liquids probably have not been investigated through this technique because putting a liquid into an ultrahigh vacuum–based microscope seems counterintuitive.” The team plans to continue their research using the new aberration-corrected low-energy electron microscope (LEEM)/PEEM system—installed through a partnership between CFN and the National Synchrotron Light Source II (NSLS-II), another DOE Office of Science User Facility at Brookhaven—at NSLS-II’s Electron Spectro-Microscopy beamline. This system will enable the team to study not only the structural and electronic changes but also the chemical changes of the ionic liquid–electrode interface—all in a single experiment. By determining these unique properties, scientists will be able to select the optimal ionic liquids for specific energy storage applications.


In the ongoing quest to pattern materials with ever-smaller feature sizes, scientists at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory—have recently set a new record. Performing EBL with a scanning transmission electron microscope (STEM), they have patterned thin films of the polymer poly(methyl methacrylate), or PMMA, with individual features as small as one nanometer (nm), and with a spacing between features of 11 nm, yielding an areal density of nearly one trillion features per square centimeter. These record achievements are published in the April 18 online edition of Nano Letters. "Our goal at CFN is to study how the optical, electrical, thermal, and other properties of materials change as their feature sizes get smaller," said lead author Vitor Manfrinato, a research associate in CFN's electron microscopy group who began the project as a CFN user while completing his doctoral work at MIT. "Until now, patterning materials at a single nanometer has not been possible in a controllable and efficient way." Commercial EBL instruments typically pattern materials at sizes between 10 and 20 nanometers. Techniques that can produce higher-resolution patterns require special conditions that either limit their practical utility or dramatically slow down the patterning process. Here, the scientists pushed the resolution limits of EBL by installing a pattern generator—an electronic system that precisely moves the electron beam over a sample to draw patterns designed with computer software—in one of CFN's aberration-corrected STEMs, a specialized microscope that provides a focused electron beam at the atomic scale. "We converted an imaging tool into a drawing tool that is capable of not only taking atomic-resolution images but also making atomic-resolution structures," said coauthor Aaron Stein, a senior scientist in the electronic nanomaterials group at CFN. Their measurements with this instrument show a nearly 200 percent reduction in feature size (from 5 to 1.7 nm) and 100 percent increase in areal pattern density (from 0.4 to 0.8 trillion dots per square centimeter, or from 16 to 11 nm spacing between features) over previous scientific reports. The team's patterned PMMA films can be used as stencils for transferring the drawn single-digit nanometer feature into any other material. In this work, the scientists created structures smaller than 5 nm in both metallic (gold palladium) and semiconducting (zinc oxide) materials. Their fabricated gold palladium features were as small as six atoms wide. Despite this record-setting demonstration, the team remains interested in understanding the factors that still limit resolution, and ultimately pushing EBL to its fundamental limit. "The resolution of EBL can be impacted by many parameters, including instrument limitations, interactions between the electron beam and the polymer material, molecular dimensions associated with the polymer structure, and chemical processes of lithography," explained Manfrinato. An exciting result of this study was the realization that polymer films can be patterned at sizes much smaller than the 26 nm effective radius of the PMMA macromolecule. "The polymer chains that make up a PMMA macromolecule are a million repeating monomers (molecules) long—in a film, these macromolecules are all entangled and balled up," said Stein. "We were surprised to find that the smallest size we could pattern is well below the size of the macromolecule and nears the size of one of the monomer repeating units, as small as a single nanometer." Next, the team plans to use their technique to study the properties of materials patterned at one-nanometer dimensions. One early target will be the semiconducting material silicon, whose electronic and optical properties are predicted to change at the single-digit nanometer scale. "This technique opens up many exciting materials engineering possibilities, tailoring properties if not atom by atom, then closer than ever before," said Stein. "Because the CFN is a national user facility, we will soon be offering our first-of-a-kind nanoscience tool to users from around the world. It will be really interesting to see how other scientists make use of this new capability." More information: Vitor R. Manfrinato et al, Aberration-Corrected Electron Beam Lithography at the One Nanometer Length Scale, Nano Letters (2017). DOI: 10.1021/acs.nanolett.7b00514


News Article | April 28, 2017
Site: www.eurekalert.org

An electron microscope-based lithography system for patterning materials at sizes as small as a single nanometer could be used to create and study materials with new properties UPTON, NY -- The ability to pattern materials at ever-smaller sizes -- using electron-beam lithography (EBL), in which an electron-sensitive material is exposed to a focused beam of electrons, as a primary method -- is driving advances in nanotechnology. When the feature size of materials is reduced from the macroscale to the nanoscale, individual atoms and molecules can be manipulated to dramatically alter material properties, such as color, chemical reactivity, electrical conductivity, and light interactions. In the ongoing quest to pattern materials with ever-smaller feature sizes, scientists at the Center for Functional Nanomaterials (CFN) -- a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory -- have recently set a new record. Performing EBL with a scanning transmission electron microscope (STEM), they have patterned thin films of the polymer poly(methyl methacrylate), or PMMA, with individual features as small as one nanometer (nm), and with a spacing between features of 11 nm, yielding an areal density of nearly one trillion features per square centimeter. These record achievements are published in the April 18 online edition of Nano Letters. "Our goal at CFN is to study how the optical, electrical, thermal, and other properties of materials change as their feature sizes get smaller," said lead author Vitor Manfrinato, a research associate in CFN's electron microscopy group who began the project as a CFN user while completing his doctoral work at MIT. "Until now, patterning materials at a single nanometer has not been possible in a controllable and efficient way." Commercial EBL instruments typically pattern materials at sizes between 10 and 20 nanometers. Techniques that can produce higher-resolution patterns require special conditions that either limit their practical utility or dramatically slow down the patterning process. Here, the scientists pushed the resolution limits of EBL by installing a pattern generator -- an electronic system that precisely moves the electron beam over a sample to draw patterns designed with computer software -- in one of CFN's aberration-corrected STEMs, a specialized microscope that provides a focused electron beam at the atomic scale. "We converted an imaging tool into a drawing tool that is capable of not only taking atomic-resolution images but also making atomic-resolution structures," said coauthor Aaron Stein, a senior scientist in the electronic nanomaterials group at CFN. Their measurements with this instrument show a nearly 200 percent reduction in feature size (from 5 to 1.7 nm) and 100 percent increase in areal pattern density (from 0.4 to 0.8 trillion dots per square centimeter, or from 16 to 11 nm spacing between features) over previous scientific reports. The team's patterned PMMA films can be used as stencils for transferring the drawn single-digit nanometer feature into any other material. In this work, the scientists created structures smaller than 5 nm in both metallic (gold palladium) and semiconducting (zinc oxide) materials. Their fabricated gold palladium features were as small as six atoms wide. Despite this record-setting demonstration, the team remains interested in understanding the factors that still limit resolution, and ultimately pushing EBL to its fundamental limit. "The resolution of EBL can be impacted by many parameters, including instrument limitations, interactions between the electron beam and the polymer material, molecular dimensions associated with the polymer structure, and chemical processes of lithography," explained Manfrinato. An exciting result of this study was the realization that polymer films can be patterned at sizes much smaller than the 26 nm effective radius of the PMMA macromolecule. "The polymer chains that make up a PMMA macromolecule are a million repeating monomers (molecules) long--in a film, these macromolecules are all entangled and balled up," said Stein. "We were surprised to find that the smallest size we could pattern is well below the size of the macromolecule and nears the size of one of the monomer repeating units, as small as a single nanometer." Next, the team plans to use their technique to study the properties of materials patterned at one-nanometer dimensions. One early target will be the semiconducting material silicon, whose electronic and optical properties are predicted to change at the single-digit nanometer scale. "This technique opens up many exciting materials engineering possibilities, tailoring properties if not atom by atom, then closer than ever before," said Stein. "Because the CFN is a national user facility, we will soon be offering our first-of-a-kind nanoscience tool to users from around the world. It will be really interesting to see how other scientists make use of this new capability." This work is supported by DOE's Office of Science. Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.


News Article | May 1, 2017
Site: www.cemag.us

The ability to pattern materials at ever-smaller sizes — using electron-beam lithography (EBL), in which an electron-sensitive material is exposed to a focused beam of electrons, as a primary method — is driving advances in nanotechnology. When the feature size of materials is reduced from the macroscale to the nanoscale, individual atoms and molecules can be manipulated to dramatically alter material properties, such as color, chemical reactivity, electrical conductivity, and light interactions. In the ongoing quest to pattern materials with ever-smaller feature sizes, scientists at the Center for Functional Nanomaterials (CFN) — a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory — have recently set a new record. Performing EBL with a scanning transmission electron microscope (STEM), they have patterned thin films of the polymer poly(methyl methacrylate), or PMMA, with individual features as small as one nanometer (nm), and with a spacing between features of 11 nm, yielding an areal density of nearly one trillion features per square centimeter. These record achievements are published in the April 18 online edition of Nano Letters. “Our goal at CFN is to study how the optical, electrical, thermal, and other properties of materials change as their feature sizes get smaller,” says lead author Vitor Manfrinato, a research associate in CFN’s electron microscopy group who began the project as a CFN user while completing his doctoral work at MIT. “Until now, patterning materials at a single nanometer has not been possible in a controllable and efficient way.” Commercial EBL instruments typically pattern materials at sizes between 10 and 20 nanometers. Techniques that can produce higher-resolution patterns require special conditions that either limit their practical utility or dramatically slow down the patterning process. Here, the scientists pushed the resolution limits of EBL by installing a pattern generator — an electronic system that precisely moves the electron beam over a sample to draw patterns designed with computer software — in one of CFN’s aberration-corrected STEMs, a specialized microscope that provides a focused electron beam at the atomic scale. “We converted an imaging tool into a drawing tool that is capable of not only taking atomic-resolution images but also making atomic-resolution structures,” says coauthor Aaron Stein, a senior scientist in the electronic nanomaterials group at CFN. Their measurements with this instrument show a nearly 200 percent reduction in feature size (from 5 to 1.7 nm) and 100 percent increase in areal pattern density (from 0.4 to 0.8 trillion dots per square centimeter, or from 16 to 11 nm spacing between features) over previous scientific reports. The team’s patterned PMMA films can be used as stencils for transferring the drawn single-digit nanometer feature into any other material. In this work, the scientists created structures smaller than 5 nm in both metallic (gold palladium) and semiconducting (zinc oxide) materials. Their fabricated gold palladium features were as small as six atoms wide. Despite this record-setting demonstration, the team remains interested in understanding the factors that still limit resolution, and ultimately pushing EBL to its fundamental limit. “The resolution of EBL can be impacted by many parameters, including instrument limitations, interactions between the electron beam and the polymer material, molecular dimensions associated with the polymer structure, and chemical processes of lithography,” explains Manfrinato. An exciting result of this study was the realization that polymer films can be patterned at sizes much smaller than the 26 nm effective radius of the PMMA macromolecule. “The polymer chains that make up a PMMA macromolecule are a million repeating monomers (molecules) long — in a film, these macromolecules are all entangled and balled up,” says Stein. “We were surprised to find that the smallest size we could pattern is well below the size of the macromolecule and nears the size of one of the monomer repeating units, as small as a single nanometer.” Next, the team plans to use their technique to study the properties of materials patterned at one-nanometer dimensions. One early target will be the semiconducting material silicon, whose electronic and optical properties are predicted to change at the single-digit nanometer scale. “This technique opens up many exciting materials engineering possibilities, tailoring properties if not atom by atom, then closer than ever before,” says Stein. “Because the CFN is a national user facility, we will soon be offering our first-of-a-kind nanoscience tool to users from around the world. It will be really interesting to see how other scientists make use of this new capability.” This work is supported by DOE’s Office of Science.


Home > Press > Water-Repellent Nanotextures Found to Have Excellent Anti-Fogging Abilities: Cone-shaped nanotextures could prevent fog condensation on surfaces in humid environments, including for power generation and transportation applications Abstract: Some insect bodies have evolved the abilities to repel water and oil, adhere to different surfaces, and eliminate light reflections. Scientists have been studying the physical mechanisms underlying these remarkable properties found in nature and mimicking them to design materials for use in everyday life. Several years ago, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory developed a nanoscale surface-texturing method for imparting complete water repellency to materials-a property inspired by insect exoskeletons that have tiny hairs designed to repel water by trapping air. Their method leverages the ability of materials called block copolymers (chains of two distinct molecules linked together) to self-assemble into ordered patterns with dimensions measuring only tens of nanometers in size. The scientists used these self-assembled patterns to create nanoscale textures in a variety of inorganic materials, including silicon, glass, and some plastics. Initially, they studied how changing the shape of the textures from cylindrical to conical impacted materials' ability to repel water. Cone-shaped nanotextures proved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry. Now, working with colleagues in France-from ESPCI Paris Tech, École Polytechnique, and the Thales Group-they have further shown that the optimized nanotextures have excellent anti-fogging abilities, as described in a paper published online in the Feb. 27 issue of Nature Materials. Led by David Quéré of ESPCI and École Polytechnique, the research provides a fundamental understanding that may inform new designs for condensing coils of steam turbine power generators, car and aircraft windshields, and other materials prone to fogging. "Many textured materials can repel water, with millimeter-size water drops bouncing off their surfaces, but many of these surfaces fail when exposed to foggy or humid conditions," said Charles Black, director of Brookhaven Lab's Center for Functional Nanomaterials [ https://www.bnl.gov/cfn/ ] (CFN), the DOE Office of Science User Facility where Black and former physicist Antonio Checco of Brookhaven's Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate Atikur Rahman fabricated the nanotextures. Fog forms when warm, moist air hits a cooler surface (such as a window or windshield) and forms water droplets-a process called condensation. When water droplets are similar in size to the structural features of a textured hydrophobic ("water hating") surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the material gets stuck, resulting in the appearance of fog. Scientists have previously observed that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the ability to repel fog by causing water droplets to spontaneously jump off their surface-a phenomenon caused by the efficient conversion of surface energy to kinetic energy when two droplets combine. Motivated by this example from nature, the team investigated how reducing texture size and changing texture shape impacts the anti-fogging ability of a model surface. To simulate fogging conditions, the scientists heated water and measured the adhesion force as warm water droplets cooled upon contacting the nanotextured surfaces. These measurements revealed that droplet adhesion was significantly affected by the type of surface nanotexture, with warm drops strongly sticking to those with large textures and hardly sticking at all to surfaces with the smallest ones. "Textures with the smallest feature sizes and the appropriate shape-in this case, conical-resist fogging because condensing water droplets are too big to penetrate the texture. The droplets remain on top, essentially floating on the cushion of air trapped beneath," said Black. The scientists next used an optical microscope connected to a high-resolution video camera to view droplet condensation on different textures during dew formation, when atmospheric moisture condenses faster than it evaporates. While all textures are initially covered by large numbers of microdroplets, over time textures with a cylindrical shape become covered in water, while the ones with a conical shape spontaneously dry themselves. Conical-shaped textures resist dew formation because the water droplets are so lightly adhered to the surface that when two drops join together, they gain enough energy to spontaneously jump off the surface, similar to the mechanism observed in cicada wings. "This work represents the excellent, multiplicative power of DOE user facilities. In this case, CFN's initial collaboration with a user from one of Brookhaven's departments led to a new international connection with different users, who carried the study of hydrophobic surfaces in new directions," said Black. This research was supported by the DOE Office of Science, the French Ministry of Defense procurement agency, and the Thales Group. About Brookhaven National Laboratory Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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