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45 results on '"Baldwin, Jon K."'

1. Light-Driven Nanoscale Vectorial Currents

Author

Pettine, Jacob, Padmanabhan, Prashant, Shi, Teng, Gingras, Lauren, McClintock, Luke, Chang, Chun-Chieh, Kwock, Kevin W. C., Yuan, Long, Huang, Yue, Nogan, John, Baldwin, Jon K., Adel, Peter, Holzwarth, Ronald, Azad, Abul K., Ronning, Filip, Taylor, Antoinette J., Prasankumar, Rohit P., Lin, Shi-Zeng, and Chen, Hou-Tong

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometer spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here, we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to sub-diffractive nanometer scales. Local symmetries and vectorial current distributions are revealed by polarization- and wavelength-sensitive electrical readout and terahertz (THz) emission, while spatially-tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams. We show that in graphene, a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to rapidly-evolving nanoscale driving forces and charge flows under extreme temporal and spatial confinement. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nano-magnetism, and ultrafast information processing.

Published
2023
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2. Light-driven nanoscale vectorial currents

Author

Pettine, Jacob, Padmanabhan, Prashant, Shi, Teng, Gingras, Lauren, McClintock, Luke, Chang, Chun-Chieh, Kwock, Kevin W. C., Yuan, Long, Huang, Yue, Nogan, John, Baldwin, Jon K., Adel, Peter, Holzwarth, Ronald, Azad, Abul K., Ronning, Filip, Taylor, Antoinette J., Prasankumar, Rohit P., Lin, Shi-Zeng, and Chen, Hou-Tong

Published
2024
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3. Perspectives on Novel Refractory Amorphous High-Entropy Alloys in Extreme Environments

Author

Tunes, Matheus A., Vo, Hi T., Baldwin, Jon K. S., Saleh, Tarik A., Fensin, Saryu J., and El-Atwani, Osman

Subjects
Condensed Matter - Materials Science, Condensed Matter - Other Condensed Matter
Abstract

Two new refractory amorphous high-entropy alloys (RAHEAs) within the W--Ta--Cr--V and W--Ta--Cr--V--Hf systems were herein synthesized using magnetron-sputtering and tested under high-temperature annealing and displacing irradiation using \textit{in situ} Transmission Electron Microscopy. While the WTaCrV RAHEA was found to be unstable under such tests, additions of Hf in this system composing a new quinary WTaCrVHf RAHEA was found to be a route to achieve stability both under annealing and irradiation. A new effect of nanoprecipitate reassembling observed to take place within the WTaCrVHf RAHEA under irradiation indicates that a duplex microstructure composed of an amorphous matrix with crystalline nanometer-sized precipitates enhances the radiation response of the system. It is demonstrated that tunable chemical complexity arises as a new alloy design strategy to foster the use of novel RAHEAs within extreme environments. New perspectives for the alloy design and application of chemically-complex amorphous metallic alloys in extreme environments are presented with focus on their thermodynamic phase stability when subjected to high-temperature annealing and displacing irradiation.

Published
2022
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11. Interface effect of Fe and Fe2O3 on the distributions of ion induced defects.

Author

Kim, Hyosim, Chancey, Matthew R., Chung, Thaihang, Brackenbury, Ian, Liedke, Maciej O., Butterling, Maik, Hirschmann, Eric, Wagner, Andreas, Baldwin, Jon K., Derby, Ben K., Li, Nan, Yano, Kayla H., Edwards, Danny J., Wang, Yongqiang, and Selim, Farida A.

Subjects
POSITRON annihilation, NUCLEAR reactor materials, POINT defects, TRANSMISSION electron microscopy, METAL defects, EXTREME environments
Abstract

The stability of structural materials in extreme nuclear reactor environments—with high temperature, high radiation, and corrosive media—directly affects the lifespan of the reactor. In such extreme environments, an oxide layer on the metal surface acts as a passive layer protecting the metal underneath from corrosion. To predict the irradiation effect on the metal layer in these metal/oxide bilayers, nondestructive depth-resolved positron annihilation lifetime spectroscopy (PALS) and complementary transmission electron microscopy (TEM) were used to investigate small-scale defects created by ion irradiation in an epitaxially grown (100) Fe film capped with a 50 nm Fe2O3 oxide layer. In this study, the evolution of induced vacancies was monitored, from individual vacancy formation at low doses—10−5 dpa—to larger vacancy cluster formation at increasing doses, showing the sensitivity of positron annihilation spectroscopy technique. Furthermore, PALS measurements reveal how the presence of a metal–oxide interface modifies the distribution of point defects induced by irradiation. TEM measurements show that irradiation induced dislocations at the interface is the mechanism behind the redistribution of point defects causing their accumulation close to the interface. This work demonstrates that the passive oxide layers formed during corrosion impact the distribution and accumulation of radiation induced defects in the metal underneath and emphasizes that the synergistic impact of radiation and corrosion will differ from their individual impacts. [ABSTRACT FROM AUTHOR]

Published
2022
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14. Enhanced van der Waals epitaxy of germanium by out-of-plane dipole moment induced from transferred graphene on TiN/AlN multilayers.

Author

Wang, Xuejing, Kim, Yeonhoo, Baldwin, Jon K., Jones, Andrew C., Jeong, Jeeyoon, Kang, Kyeong Tae, Chen, Aiping, and Yoo, Jinkyoung

Subjects
TITANIUM nitride, DIPOLE moments, KELVIN probe force microscopy, ADATOMS, EPITAXY, SURFACE energy, SEMICONDUCTOR thin films
Abstract

Recent advances in 3D/2D heterostructures have opened up tremendous opportunities in building highly flexible and durable optoelectronic devices. However, the inherit lack of interfacial bonding and low surface energy of van der Waals surfaces limit the nucleation and growth of 3D materials. Enhancing wettability by providing a porous buffer is effective in growing compound semiconductors on graphene while van der Waals epitaxy of Ge remains challenging. Here, the nucleation of Ge has been significantly improved from an islanded mode to granular modes by using a TiN/AlN multilayered buffer prior to Ge/graphene integration. Highly textured Ge growth with dominating (111), (220), and (311) peaks are identified by x-ray diffraction. The microstructure of the buffer TiN/AlN demonstrates a polycrystalline quality with clean interfaces between each interlayer and the substrate. Kelvin probe force microscopy measurements along the lateral TiN/AlN interface identify a potential drop corresponding to the AlN phase. This contact potential difference between TiN and AlN is the key in generating the out-of-plane dipole moment that modifies the surface energy of the monolayer graphene, resulting in enhanced wettability of the Ge adatoms nucleated on top. Surface dipole induced nucleation of 3D semiconductor thin films on 2D materials via the proper design of buffer layer is fundamentally important to enhance the 3D/2D growth toward flexible optoelectronic applications. [ABSTRACT FROM AUTHOR]

Published
2021
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16. Interface effect of Fe and Fe2O3 on the distributions of ion induced defects

Author

Kim, Hyosim, primary, Chancey, Matthew R., additional, Chung, Thaihang, additional, Brackenbury, Ian, additional, Liedke, Maciej O., additional, Butterling, Maik, additional, Hirschmann, Eric, additional, Wagner, Andreas, additional, Baldwin, Jon K., additional, Derby, Ben K., additional, Li, Nan, additional, Yano, Kayla H., additional, Edwards, Danny J., additional, Wang, Yongqiang, additional, and Selim, Farida A., additional

Published
2022
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36. Ozonated Graphene Oxide Film as a Proton-Exchange Membrane

Author

Gao, Wei, primary, Wu, Gang, additional, Janicke, Michael T., additional, Cullen, David A., additional, Mukundan, Rangachary, additional, Baldwin, Jon K., additional, Brosha, Eric L., additional, Galande, Charudatta, additional, Ajayan, Pulickel M., additional, More, Karren L., additional, Dattelbaum, Andrew M., additional, and Zelenay, Piotr, additional

Published
2014
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43. Nitrogen-Doped Graphene-Rich Catalysts Derived from Heteroatom Polymers for Oxygen Reduction in Nonaqueous Lithium–O2Battery Cathodes

Author

Wu, Gang, Mack, Nathan H., Gao, Wei, Ma, Shuguo, Zhong, Ruiqin, Han, Jiantao, Baldwin, Jon K., and Zelenay, Piotr

Abstract

In this work, we present a synthesis approach for nitrogen-doped graphene-sheet-like nanostructures viathe graphitization of a heteroatom polymer, in particular, polyaniline, under the catalysis of a cobalt species using multiwalled carbon nanotubes (MWNTs) as a supporting template. The graphene-rich composite catalysts (Co-N-MWNTs) exhibit substantially improved activity for oxygen reduction in nonaqueous lithium-ion electrolyte as compared to those of currently used carbon blacks and Pt/carbon catalysts, evidenced by both rotating disk electrode and Li–O2battery experiments. The synthesis–structure–activity correlations for the graphene nanostructures were explored by tuning their synthetic chemistry (support, nitrogen precursor, heating temperature, and transition metal type and content) to investigate how the resulting morphology and nitrogen-doping functionalities (e.g., pyridinic, pyrrolic, and quaternary) influence the catalyst activity. In particular, an optimal temperature for heat treatment during synthesis is critical to creating a high-surface-area catalyst with favorable nitrogen doping. The sole Co phase, Co9S8, was present in the catalyst but plays a negligible role in ORR. Nevertheless, the addition of Co species in the synthesis is indispensable for achieving high activity, due to its effects on the final catalyst morphology and structure, including surface area, nitrogen doping, and graphene formation. This new route for the preparation of a nitrogen-doped graphene nanocomposite with carbon nanotube offers synthetic control of morphology and nitrogen functionality and shows promise for applications in nonaqueous oxygen reduction electrocatalysis for Li–O2battery cathodes.

Published
2012
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45. Ozonated graphene oxide film as a proton-exchange membrane.

Author

Gao W, Wu G, Janicke MT, Cullen DA, Mukundan R, Baldwin JK, Brosha EL, Galande C, Ajayan PM, More KL, Dattelbaum AM, and Zelenay P

Abstract

Graphene oxide (GO) contains several chemical functional groups that are attached to the graphite basal plane and can be manipulated to tailor GO for specific applications. It is now revealed that the reaction of GO with ozone results in a high level of oxidation, which leads to significantly improved ionic (protonic) conductivity of the GO. Freestanding ozonated GO films were synthesized and used as efficient polymer electrolyte fuel cell membranes. The increase in protonic conductivity of the ozonated GO originates from enhanced proton hopping, which is due to the higher content of oxygenated functional groups in the basal planes and edges of ozonated GO as well as the morphology changes in GO that are caused by ozonation. The results of this study demonstrate that the modification of dispersed GO presents a powerful opportunity for optimizing a nanoscale material for proton-exchange membranes.

Published
2014
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