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Wang M, Xue T, Miao H, Wu W, Zhang Z, Han M, Liu X, Li X. High χ P2PFBEMA- b-P2VP Block Copolymers Forming 6-8 nm Domains for Semiconductor Lithography. ACS APPLIED MATERIALS & INTERFACES 2024; 16:31586-31596. [PMID: 38837344 DOI: 10.1021/acsami.4c05301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
We leveraged the potential of high χ-low N block copolymer (BCP), namely, poly[2-(perfluorobutyl) ethyl methacrylate]-block-poly(2-vinylpyridine) (P2PFBEMA-b-P2VP), and demonstrated its utility in next-generation nanomanufacturing. By combining molecular dynamics simulations with experiments, the χ value was calculated to be as high as 0.4 (at 150 °C), surpassing similar structures. Highly ordered features suitable for application were observed, ranging in periods from 19.0 nm down to 12.1 nm, with feature sizes as small as 6 nm. Transmission electron microscopy images of the BCP solutions indicated that preformed micelles in the solution facilitated the self-assembly process of the thin film. In addition, the vertical or parallel orientation of the cylindrical structure was determined by manipulating the solvent, substrate, and annealing conditions. Finally, guided by a wide topographical template, nearly defect-free directed self-assembly (DSA) lines with a resolution of 8 nm were achieved, highlighting its potential practical application in DSA lithography technology.
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Affiliation(s)
- Mengge Wang
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Tao Xue
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Han Miao
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Wanqing Wu
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Zhipeng Zhang
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Muzi Han
- School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Xianhe Liu
- School of Microelectronics, Fudan University, Shanghai 200433, China
| | - Xinxin Li
- Key Laboratory of Specially Functional Polymeric Materials and Related Technology (Ministry of Education), School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
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2
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Putranto AF, Petit-Etienne C, Cavalaglio S, Cabannes-Boué B, Panabiere M, Forcina G, Fleury G, Kogelschatz M, Zelsmann M. Controlled Anisotropic Wetting by Plasma Treatment for Directed Self-Assembly of High-χ Block Copolymers. ACS APPLIED MATERIALS & INTERFACES 2024; 16:27841-27849. [PMID: 38758246 DOI: 10.1021/acsami.4c01657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
The directed self-assembly (DSA) of block copolymers (BCPs) is a promising next-generation lithography technique for high-resolution patterning. However, achieving lithographically applicable BCP organization such as out-of-plane lamellae requires proper tuning of interfacial energies between the BCP domains and the substrate, which remains difficult to address effectively and efficiently with high-χ BCPs. Here, we present the successful generation of anisotropic wetting by plasma treatment on patterned spin-on-carbon (SOC) substrates and its application to the DSA of a high-χ Si-containing material, poly(1,1-dimethylsilacyclobutane)-block-polystyrene (PDMSB-b-PS), with a 9 nm half pitch. Exposing the SOC substrate to different plasma chemistries promotes the vertical alignment of the PDMSB-b-PS lamellae within the trenches. In particular, a patterned substrate treated with HBr/O2 plasma gives both a neutral wetting at the bottom interface and a strong PS-affine wetting at the sidewalls of the SOC trenches to efficiently guide the vertical BCP lamellae. Furthermore, prolonged exposure to HBr/O2 plasma enables an adjustment of the trench width and an increased density of BCP lines on the substrate. Experimental observations are in agreement with a free energy configurational model developed to describe the system. These advances, which could be easily implemented in industry, could contribute to the wider adoption of self-assembly techniques in microelectronics, and beyond to applications such as metasurfaces, surface-enhanced Raman spectroscopy, and sensing technologies.
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Affiliation(s)
- Achmad Fajar Putranto
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | - Camille Petit-Etienne
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | - Sébastien Cavalaglio
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | | | - Marie Panabiere
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | - Gianluca Forcina
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | - Guillaume Fleury
- CNRS, Bordeaux INP, LCPO, UMR 5629, Univ. Bordeaux, F-33600 Pessac, France
| | - Martin Kogelschatz
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
| | - Marc Zelsmann
- CNRS, CEA/LETI Minatec, Laboratoire des Technologies de la Microélectronique (LTM), Université Grenoble Alpes, 38000 Grenoble, France
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Cho J, Oh J, Bang J, Koh JH, Jeong HY, Chung S, Son JG. Roll-to-plate 0.1-second shear-rolling process at elevated temperature for highly aligned nanopatterns. Nat Commun 2023; 14:8412. [PMID: 38110407 PMCID: PMC10728125 DOI: 10.1038/s41467-023-43766-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 11/18/2023] [Indexed: 12/20/2023] Open
Abstract
The shear-rolling process is a promising directed self-assembly method that can produce high-quality sub-10 nm block copolymer line-space patterns cost-effectively and straightforwardly over a large area. This study presents a high temperature (280 °C) and rapid (~0.1 s) shear-rolling process that can achieve a high degree of orientation in a single process while effectively preventing film delamination, that can be applied to large-area continuous processes. By minimizing adhesion, normal forces, and ultimate shear strain of the polydimethylsiloxane pad, shearing was successfully performed without peeling up to 280 °C at which the chain mobility significantly increases. This method can be utilized for various high-χ block copolymers and surface neutralization processes. It enables the creation of block copolymer patterns with a half-pitch as small as 8 nm in a unidirectional way. Moreover, the 0.1-second rapid shear-rolling was successfully performed on long, 3-inch width polyimide flexible films to validate its potential for the roll-to-roll process.
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Affiliation(s)
- Junghyun Cho
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea
| | - Jinwoo Oh
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea
| | - Joona Bang
- Department of Chemical and Biological Engineering, Korea University, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Jai Hyun Koh
- Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea
| | - Hoon Yeub Jeong
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea
| | - Seungjun Chung
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Jeong Gon Son
- Soft Hybrid Materials Research Center, Korea Institute of Science and Technology (KIST), Seongbuk-gu, Seoul, 02792, Republic of Korea.
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul, 02841, Republic of Korea.
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Ginige G, Song Y, Olsen BC, Luber EJ, Yavuz CT, Buriak JM. Solvent Vapor Annealing, Defect Analysis, and Optimization of Self-Assembly of Block Copolymers Using Machine Learning Approaches. ACS APPLIED MATERIALS & INTERFACES 2021; 13:28639-28649. [PMID: 34100583 DOI: 10.1021/acsami.1c05056] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Self-assembly of block copolymers (BCPs) is an alternative patterning technique that promises high resolution and density multiplication with lower costs. The defectivity of the resulting nanopatterns remains too high for many applications in microelectronics and is exacerbated by small variations of processing parameters, such as film thickness, and fluctuations of solvent vapor pressure and temperature, among others. In this work, a solvent vapor annealing (SVA) flow-controlled system is combined with design of experiments (DOE) and machine learning (ML) approaches. The SVA flow-controlled system enables precise optimization of the conditions of self-assembly of the high Flory-Huggins interaction parameter (χ) hexagonal dot-array forming BCP, poly(styrene-b-dimethylsiloxane) (PS-b-PDMS). The defects within the resulting patterns at various length scales are then characterized and quantified. The results show that the defectivity of the resulting nanopatterned surfaces is highly dependent upon very small variations of the initial film thicknesses of the BCP, as well as the degree of swelling under the SVA conditions. These parameters also significantly contribute to the quality of the resulting pattern with respect to grain coarsening, as well as the formation of different macroscale phases (single and double layers and wetting layers). The results of qualitative and quantitative defect analyses are then compiled into a single figure of merit (FOM) and are mapped across the experimental parameter space using ML approaches, which enable the identification of the narrow region of optimum conditions for SVA for a given BCP. The result of these analyses is a faster and less resource intensive route toward the production of low-defectivity BCP dot arrays via rational determination of the ideal combination of processing factors. The DOE and machine learning-enabled approach is generalizable to the scale-up of self-assembly-based nanopatterning for applications in electronic microfabrication.
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Affiliation(s)
- Gayashani Ginige
- Department of Chemistry, University of Alberta, 11227-Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Youngdong Song
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Brian C Olsen
- Department of Chemistry, University of Alberta, 11227-Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Erik J Luber
- Department of Chemistry, University of Alberta, 11227-Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Cafer T Yavuz
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
- KAUST Catalysis Center (KCC), Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
- Advanced Membranes and Porous Materials Center (AMPM), Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Jillian M Buriak
- Department of Chemistry, University of Alberta, 11227-Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
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Abate AA, Piqueras CM, Vega DA. Defect-Induced Order–Order Phase Transition in Triblock Copolymer Thin Films. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anabella A. Abate
- Department of Physics. Instituto de Física del Sur (IFISUR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina
| | - Cristian M. Piqueras
- Department of Chemical Engineering. Planta Piloto de Ingeniería Química (PLAPIQUI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina
| | - Daniel A. Vega
- Department of Physics. Instituto de Física del Sur (IFISUR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina
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Pinto-Gómez C, Pérez-Murano F, Bausells J, Villanueva LG, Fernández-Regúlez M. Directed Self-Assembly of Block Copolymers for the Fabrication of Functional Devices. Polymers (Basel) 2020; 12:E2432. [PMID: 33096908 PMCID: PMC7589734 DOI: 10.3390/polym12102432] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/15/2020] [Accepted: 10/16/2020] [Indexed: 01/17/2023] Open
Abstract
Directed self-assembly of block copolymers is a bottom-up approach to nanofabrication that has attracted high interest in recent years due to its inherent simplicity, high throughput, low cost and potential for sub-10 nm resolution. In this paper, we review the main principles of directed self-assembly of block copolymers and give a brief overview of some of the most extended applications. We present a novel fabrication route based on the introduction of directed self-assembly of block copolymers as a patterning option for the fabrication of nanoelectromechanical systems. As a proof of concept, we demonstrate the fabrication of suspended silicon membranes clamped by dense arrays of single-crystal silicon nanowires of sub-10 nm diameter. Resulting devices can be further developed for building up high-sensitive mass sensors based on nanomechanical resonators.
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Affiliation(s)
- Christian Pinto-Gómez
- Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain; (C.P.-G.); (F.P.-M.); (J.B.)
| | - Francesc Pérez-Murano
- Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain; (C.P.-G.); (F.P.-M.); (J.B.)
| | - Joan Bausells
- Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain; (C.P.-G.); (F.P.-M.); (J.B.)
| | - Luis Guillermo Villanueva
- Advanced NEMS Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland;
| | - Marta Fernández-Regúlez
- Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain; (C.P.-G.); (F.P.-M.); (J.B.)
- Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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7
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Kim DH, Kim SY. Universal Interfacial Control through Polymeric Nanomosaic Coating for Block Copolymer Nanopatterning. ACS NANO 2020; 14:7140-7151. [PMID: 32469492 DOI: 10.1021/acsnano.0c01957] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The employment of self-assembly of soft materials has been accepted as an inexpensive, robust, and reliable patterning method. As their self-assembly relies on the delicate molecular interactions near the substrate, a precise prediction/control of the interface structure and dynamics is critical to achieve desired nanostructures. Herein, a polymeric nanomosaic (PNM) pattern is created from the air/water interfacial self-assembly of a block copolymer (BCP) and introduced as an effective interfacial energy control for substrates. As a demonstration, the PNM coating is employed to control the BCP film structures. The perpendicular orientation of BCP self-assembly, which requires neutral wetting conditions for both blocks, is difficult to achieve but can readily be obtained with the PNM coating upon a fine resolution of the pattern quality. The universal applicability of the PNM coating as an interfacial control has been confirmed on curved, flexible, and three-dimensional substrates. In addition, the PNM is introduced as an etching-free and reusable topcoat imparting free surface neutralization even for the high-χ BCP nanopatterning.
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Affiliation(s)
- Dong Hyup Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, Republic of Korea
| | - So Youn Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, Republic of Korea
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Seguini G, Zanenga F, Cannetti G, Perego M. Thermodynamics and ordering kinetics in asymmetric PS-b-PMMA block copolymer thin films. SOFT MATTER 2020; 16:5525-5533. [PMID: 32500912 DOI: 10.1039/d0sm00441c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The ordering kinetics of standing cylinder-forming polystyrene-block-poly(methyl methacrylate) block copolymers (molecular weight: 39 kg mol-1) close to the order-disorder transition is experimentally investigated following the temporal evolution of the correlation length at different annealing temperatures. The growth exponent of the grain-coarsening process is determined to be 1/2, signature of a curvature-driven ordering mechanism. The measured activation enthalpy and the resulting Meyer-Neldel temperature for this specific copolymer along with the data already known for PS-b-PMMA block copolymers in strong segregation limit allow investigation of the interplay between the ordering kinetics and the thermodynamic driving force during the grain coarsening. These findings unveil various phenomena concomitantly occurring during the thermally activated ordering kinetics at segmental, single chain, and collective levels.
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Affiliation(s)
- Gabriele Seguini
- IMM-CNR, Unit of Agrate Brianza, Via C. Olivetti 2, I-20864 Agrate Brianza, Italy.
| | - Fabio Zanenga
- IMM-CNR, Unit of Agrate Brianza, Via C. Olivetti 2, I-20864 Agrate Brianza, Italy.
| | - Gianluca Cannetti
- IMM-CNR, Unit of Agrate Brianza, Via C. Olivetti 2, I-20864 Agrate Brianza, Italy.
| | - Michele Perego
- IMM-CNR, Unit of Agrate Brianza, Via C. Olivetti 2, I-20864 Agrate Brianza, Italy.
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Kim JY, Liu P, Maher MJ, Callan DH, Bates CM, Carlson MC, Asano Y, Blachut G, Rettner CT, Cheng JY, Sunday DF, Kline RJ, Sanders DP, Lynd NA, Ellison CJ, Willson CG, Baiz CR. Spatial Control of the Self-assembled Block Copolymer Domain Orientation and Alignment on Photopatterned Surfaces. ACS APPLIED MATERIALS & INTERFACES 2020; 12:23399-23409. [PMID: 32345022 DOI: 10.1021/acsami.0c02997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Polarity-switching photopatternable guidelines can be directly used to both orient and direct the self-assembly of block copolymers. We report the orientation and alignment of poly(styrene-block-4-trimethylsilylstyrene) (PS-b-PTMSS) with a domain periodicity, L0, of 44 nm on thin photopatternable grafting surface treatments (pGSTs) and cross-linkable surface treatments (pXSTs), containing acid-labile 4-tert-butoxystyrene monomer units. The surface treatment was exposed using electron beam lithography to create well-defined linear arrays of neutral and preferential regions. Directed self-assembly (DSA) of PS-b-PTMSS with much lower defectivity was observed on pXST than on pGST guidelines. The study of the effect of film thickness on photoacid diffusion by Fourier transform infrared spectroscopy and near-edge X-ray absorption fine structure spectroscopy suggested slower diffusion in thinner films, potentially enabling production of guidelines with sharper interfaces between the unexposed and exposed lines, and thus, the DSA of PS-b-PTMSS on thinner pXST guidelines resulted in better alignment control.
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Affiliation(s)
- Ji Yeon Kim
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Philip Liu
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Michael J Maher
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
- IBM Research - Almaden, 650 Harry Road, San Jose, California 95120, United States
- Department of Chemical Engineering and Material Science, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Devon H Callan
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Christopher M Bates
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Matthew C Carlson
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
- Department of Chemical Engineering and Material Science, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Yusuke Asano
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Gregory Blachut
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Charles T Rettner
- IBM Research - Almaden, 650 Harry Road, San Jose, California 95120, United States
| | - Joy Y Cheng
- IBM Research - Almaden, 650 Harry Road, San Jose, California 95120, United States
| | - Daniel F Sunday
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - R Joseph Kline
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Daniel P Sanders
- IBM Research - Almaden, 650 Harry Road, San Jose, California 95120, United States
| | - Nathaniel A Lynd
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Christopher J Ellison
- Department of Chemical Engineering and Material Science, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, United States
| | - C Grant Willson
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Carlos R Baiz
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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