Publications
Aizenberg, Joanna; He, Ximin; Kang, Sung Hoon; Wong, Tak-Sing
Anti-counterfeiting methods Technical Report
2013, (U.S. Patent No. 9,937,743 B2).
@techreport{Aizenberg2012,
title = {Anti-counterfeiting methods},
author = {Joanna Aizenberg and Ximin He and Sung Hoon Kang and Tak-Sing Wong},
year = {2013},
date = {2013-05-31},
note = {U.S. Patent No. 9,937,743 B2},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
Kang, Sung Hoon; Shan, Sicong; Noorduin, Wim L.; Khan, Mughees; Aizenberg, Joanna; Bertoldi, Katia
Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures Journal Article
In: Advanced Materials, vol. 25, pp. 3380-3385, 2013, (SHK, SS, and WLN contributed equally. Highlighted in the June 2013 issue of Nature Physics).
@article{Kang2013,
title = {Buckling-Induced Reversible Symmetry Breaking and Chiral Amplification Using Supported Cellular Structures},
author = {Sung Hoon Kang and Sicong Shan and Wim L. Noorduin and Mughees Khan and Joanna Aizenberg and Katia Bertoldi},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201300617/abstract},
year = {2013},
date = {2013-05-02},
journal = {Advanced Materials},
volume = {25},
pages = {3380-3385},
abstract = {Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli. },
note = {SHK, SS, and WLN contributed equally.
Highlighted in the June 2013 issue of Nature Physics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Grinthal, Alison; Kang, Sung Hoon; Epstein, Alexander K.; Aizenberg, Michael; Khan, Mughees; Aizenberg, Joanna
Steering Nanofibers: An Integrative Approach to Bio-Inspired Fiber Fabrication and Assembly Journal Article
In: Nano Today, vol. 7, pp. 35-52, 2012, (Invited Review).
@article{Grinthal2012,
title = {Steering Nanofibers: An Integrative Approach to Bio-Inspired Fiber Fabrication and Assembly},
author = {Alison Grinthal and Sung Hoon Kang and Alexander K. Epstein and Michael Aizenberg and Mughees Khan and Joanna Aizenberg},
url = {http://www.sciencedirect.com/science/article/pii/S1748013211001411},
year = {2012},
date = {2012-02-01},
journal = {Nano Today},
volume = {7},
pages = {35-52},
abstract = {As seen throughout the natural world, nanoscale fibers exhibit a unique combination of mechanical and surface properties that enable them to wind and bend around each other into an immense diversity of complex forms. In this review, we discuss how this versatility can be harnessed to transform a simple array of anchored nanofibers into a variety of complex, hierarchically organized dynamic functional surfaces. We describe a set of recently developed benchtop techniques that provide a straightforward way to generate libraries of fibrous surfaces with a wide range of finely tuned, nearly arbitrary geometric, mechanical, material, and surface characteristics starting from a single master array. These simple systematic controls can be used to program the fibers to bundle together, twist around each other into chiral swirls, and assemble into patterned arrays of complex hierarchical architectures. The delicate balance between fiber elasticity and surface adhesion plays a critical role in determining the shape, chirality, and higher order of the assembled structures, as does the dynamic evolution of the geometric, mechanical, and surface parameters throughout the assembly process. Hierarchical assembly can also be programmed to run backwards, enabling a wide range of reversible, responsive behaviors to be encoded through rationally chosen surface chemistry. These strategies provide a foundation for designing a vast assortment of functional surfaces with anti-fouling, adhesive, optical, water and ice repellent, memory storage, microfluidic, capture and release, and many more capabilities with the structural and dynamic sophistication of their biological counterparts.},
note = {Invited Review},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Aizenberg, Joanna; Aizenberg, Michael; Kang, Sung Hoon; Kim, Philseok; Tang, Kam Yan; Wong, Tak- Sing
Slippery Surfaces with High Pressure Stability, Optical Transparency, and Self-Healing Characteristics Technical Report
2012, (United States Patent 9,121,306 and 9,121,307).
@techreport{Aizenberg2012b,
title = {Slippery Surfaces with High Pressure Stability, Optical Transparency, and Self-Healing Characteristics},
author = {Joanna Aizenberg and Michael Aizenberg and Sung Hoon Kang and Philseok Kim and Kam Yan Tang and Tak- Sing Wong},
url = {http://www.google.com/patents/US9121306},
year = {2012},
date = {2012-01-19},
note = {United States Patent 9,121,306 and 9,121,307},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
Kang, Sung Hoon; Wu, Ning; Grinthal, Alison; Aizenberg, Joanna
Meniscus Lithography: Evaporation-Induced Self-Organization of Pillar Arrays into Moiré Patterns Journal Article
In: Physical Review Letters, vol. 107, pp. 177802, 2011, (Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Today and Physics Synopsis. ).
@article{Kang2011,
title = {Meniscus Lithography: Evaporation-Induced Self-Organization of Pillar Arrays into Moiré Patterns},
author = {Sung Hoon Kang and Ning Wu and Alison Grinthal and Joanna Aizenberg},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.107.177802},
year = {2011},
date = {2011-10-20},
journal = {Physical Review Letters},
volume = {107},
pages = {177802},
abstract = {We demonstrate a self-organizing system that generates patterns by dynamic feedback: two periodic surfaces collectively structure an intervening liquid sandwiched between them, which then reconfigures the original surface features into moiré patterns as it evaporates. Like the conventional moiré phenomenon, the patterns are deterministic and tunable by mismatch angle, yet additional behaviors—chirality from achiral starting motifs and preservation of the patterns after the surfaces are separated—emerge uniquely from the feedback process. Patterning menisci based on this principle provides a simple, scalable approach for making a series of complex, long-range-ordered structures.},
note = {Selected as Physical Review Letters Editors’ Suggestion and Highlighted in Physics Today and Physics Synopsis. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Wong, Tak-Sing; Kang, Sung Hoon; Tang, Sindy. K. Y.; Smythe, Elizabeth J.; Hatton, Benjamin D.; Grinthal, Alison; Aizenberg, Joanna
Bioinspired Self-Repairing Slippery Surfaces with Pressure-Stable Omniphobicity Journal Article
In: Nature, vol. 477, pp. 443–447, 2011, (Image Credits: James C. Weaver and Peter Allen. Selected for 2012 R&D 100 Award. Featured on News & Views, highlighted in the issue of Nature and various media worldwide including BBC, the Times, Daily Mail, ABC (Australia & Spain), Discovery, Financial Times, Yahoo News (UK), Agence France-Presse, Sina (China), the Statesman (India), Nature Chemistry, Hot Topic Article in Nature Asia-Pacific, C&EN, AAAS EurekAlert, Chemistry World, Physics World, Spektrum Der Wissenschaft, New Scientist, and the Engineer).
@article{Wong2011,
title = {Bioinspired Self-Repairing Slippery Surfaces with Pressure-Stable Omniphobicity},
author = {Tak-Sing Wong and Sung Hoon Kang and Sindy. K. Y. Tang and Elizabeth J. Smythe and Benjamin D. Hatton and Alison Grinthal and Joanna Aizenberg},
url = {http://www.nature.com/nature/journal/v477/n7365/full/nature10447.html},
year = {2011},
date = {2011-09-22},
journal = {Nature},
volume = {477},
pages = {443–447},
abstract = {Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging1. Inspirations from natural nonwetting structures2, 3, 4, 5, 6, particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air–liquid interface7, 8, 9. Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis9, failure under pressure10, 11, 12 and upon physical damage1, 7, 11, inability to self-heal and high production cost1, 11. To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach—inspired by Nepenthes pitcher plants13—is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert ‘slippery’ interface. This surface outperforms its natural counterparts2, 3, 4, 5, 6 and state-of-the-art synthetic liquid-repellent surfaces8, 9, 14, 15, 16 in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1–1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments.},
note = {Image Credits: James C. Weaver and Peter Allen.
Selected for 2012 R&D 100 Award.
Featured on News & Views, highlighted in the issue of Nature and various media worldwide including BBC, the Times, Daily Mail, ABC (Australia & Spain), Discovery, Financial Times, Yahoo News (UK), Agence France-Presse, Sina (China), the Statesman (India), Nature Chemistry, Hot Topic Article in Nature Asia-Pacific, C&EN, AAAS EurekAlert, Chemistry World, Physics World, Spektrum Der Wissenschaft, New Scientist, and the Engineer},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Seminara, Agnese; Pokroy, Boaz; Kang, Sung Hoon; Brenner, Michael P.; Aizenberg, Joanna
On the Mechanism of Nanostructure Movement under Electron Beam and Its Application in Patterning Journal Article
In: Physical Review B, vol. 83, pp. 235438, 2011.
@article{Seminara2011,
title = {On the Mechanism of Nanostructure Movement under Electron Beam and Its Application in Patterning},
author = {Agnese Seminara and Boaz Pokroy and Sung Hoon Kang and Michael P. Brenner and Joanna Aizenberg},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.83.235438},
year = {2011},
date = {2011-06-30},
journal = {Physical Review B},
volume = {83},
pages = {235438},
abstract = {In electron microscopy, the motion of the sample features due to the interaction with the electron beam has been traditionally regarded as a detrimental effect. Uncontrolled feature displacement produces artifacts both in imaging and patterning, limiting the resolution and distorting precise nanoscale patterns. The mechanism of such motion remains largely unclear. We present an experimental study of e-beam-induced nanopost movement and offer a mechanistic theoretical model that quantitatively explains the physical phenomenon. We propose that e-beam bombardment produces an uneven distribution of electrons in the sample, and the resulting electrostatic interactions provide forces and torques sufficient to bend the nanoposts. We compare the theoretical predictions with a series of controlled experiments that support our model. We take advantage of this theoretical understanding to demonstrate how this generally undesirable effect can be turned into an unconventional e-beam writing technique to generate pseudo-three-dimensional structures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lipomi, Darren J.; Martinez, Ramses V.; Kats, Mikhail A.; Kang, Sung Hoon; Kim, Philseok; Aizenberg, Joanna; Capasso, Federico; Whitesides, George M.
Patterning the Tips of Optical Fibers with Metallic Nanostructures Using Nanoskiving Journal Article
In: Nano Letters, vol. 11, pp. 632–636, 2011.
@article{Lipomi2010,
title = {Patterning the Tips of Optical Fibers with Metallic Nanostructures Using Nanoskiving},
author = {Darren J. Lipomi and Ramses V. Martinez and Mikhail A. Kats and Sung Hoon Kang and Philseok Kim and Joanna Aizenberg and Federico Capasso and George M. Whitesides},
url = {http://pubs.acs.org/doi/abs/10.1021/nl103730g},
year = {2011},
date = {2011-01-04},
journal = {Nano Letters},
volume = {11},
pages = {632–636},
abstract = {Convenient and inexpensive methods to pattern the facets of optical fibers with metallic nanostructures would enable many applications. This communication reports a method to generate and transfer arrays of metallic nanostructures to the cleaved facets of optical fibers. The process relies on nanoskiving, in which an ultramicrotome, equipped with a diamond knife, sections epoxy nanostructures coated with thin metallic films and embedded in a block of epoxy. Sectioning produces arrays of nanostructures embedded in thin epoxy slabs, which can be transferred manually to the tips of optical fibers at a rate of approximately 2 min−1, with 88% yield. Etching the epoxy matrices leaves arrays of nanostructures supported directly by the facets of the optical fibers. Examples of structures transferred include gold crescents, rings, high-aspect-ratio concentric cylinders, and gratings of parallel nanowires.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kang, Sung Hoon; Pokroy, Boaz; Mahadevan, L.; Aizenberg, Joanna
Control of Shape and Size of Nanopillar Assembly by Adhesion-Mediated Elastocapillary Interaction Journal Article
In: ACS Nano, vol. 4, pp. 6323–6331, 2010, (Featured on the cover and highlighted in the issue.).
@article{Kang2010,
title = {Control of Shape and Size of Nanopillar Assembly by Adhesion-Mediated Elastocapillary Interaction},
author = {Sung Hoon Kang and Boaz Pokroy and L. Mahadevan and Joanna Aizenberg},
url = {http://pubs.acs.org/doi/abs/10.1021/nn102260t},
year = {2010},
date = {2010-11-01},
journal = {ACS Nano},
volume = {4},
pages = {6323–6331},
abstract = {Control of self-organization of nanofibers into regular clusters upon evaporation-induced assembly is receiving increasing attention due to the potential importance of this process in a range of applications including particle trapping, adhesives, and structural color. Here we present a comprehensive study of this phenomenon using a periodic array of polymeric nanopillars with tunable parameters as a model system to study how geometry, mechanical properties, as well as surface properties influence capillary-induced self-organization. In particular, we show that varying the parameters of the building blocks of self-assembly provides us with a simple means of controlling the size, chirality, and anisotropy of complex structures. We observe that chiral assemblies can be generated within a narrow window for each parameter even in the absence of chiral building blocks or a chiral environment. Furthermore, introducing anisotropy in the building blocks provides a way to control both the chirality and the size of the assembly. While capillary-induced self-assembly has been studied and modeled as a quasi-static process involving the competition between only capillary and elastic forces, our results unequivocally show that both adhesion and kinetics are equally important in determining the final assembly. Our findings provide insight into how multiple parameters work together in capillary-induced self-assembly and provide us with a diverse set of options for fabricating a variety of nanostructures by self-assembly.},
note = {Featured on the cover and highlighted in the issue.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Pokroy, Boaz; Aichmayer, Barbara; Schenk, Anna S.; Haimov, Boris; Kang, Sung Hoon; Fratzl, Peter; Aizenberg, Joanna
Sonication-Assisted Synthesis of Large, High-Quality Mercury-Thiolate Single Crystals Directly from Liquid Mercury Journal Article
In: Journal of the American Chemical Society, vol. 132, pp. 14355–14357, 2010, (Highlighted on C&EN.).
@article{Pokroy2010,
title = {Sonication-Assisted Synthesis of Large, High-Quality Mercury-Thiolate Single Crystals Directly from Liquid Mercury},
author = {Boaz Pokroy and Barbara Aichmayer and Anna S. Schenk and Boris Haimov and Sung Hoon Kang and Peter Fratzl and Joanna Aizenberg},
url = {http://pubs.acs.org/doi/abs/10.1021/ja1056449},
year = {2010},
date = {2010-09-27},
journal = {Journal of the American Chemical Society},
volume = {132},
pages = {14355–14357},
abstract = {The synthetic formation of mercury thiolates has been known for almost 200 years. These compounds are usually formed by a slow reaction of mercury salts with thiolates or disulfides to produce small (up to 1 μm), plate-like crystals of Hg(S-R)2. Herein we show that such mercury thiolates can be formed directly from liquid mercury via sonication with neat thiols. The process not only produces crystals very rapidly (within seconds) but also leads to the formation of large crystals (up to hundreds of micrometers). The high quality of these crystals enabled their detailed structural characterization, which showed that the crystals are composed of ordered Hg(thiol)2 stacks. We extended the experimental procedure to form and characterize a range of Hg thiolate crystals with various chain lengths. We propose a new self-assembly mechanism that can explain how sonication—which is usually used to break chemical bonds, to disperse materials, and to form nanosized crystallites—may lead to the growth of large, high-quality crystals.},
note = {Highlighted on C&EN.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lipomi, Darren J.; Kats, Mikhail A.; Kim, Philseok; Kang, Sung Hoon; Aizenberg, Joanna; Capasso, Federico; Whitesides, George M.
Fabrication and Replication of Arrays of Single- or Multi-Component Nanostructures by Replica Molding and Mechanical Sectioning Journal Article
In: ACS Nano, vol. 4, pp. 4017–4026, 2010, (Featured on the cover and highlighted in the issue.).
@article{Lipomi2010b,
title = {Fabrication and Replication of Arrays of Single- or Multi-Component Nanostructures by Replica Molding and Mechanical Sectioning},
author = {Darren J. Lipomi and Mikhail A. Kats and Philseok Kim and Sung Hoon Kang and Joanna Aizenberg and Federico Capasso and George M. Whitesides},
url = {http://pubs.acs.org/doi/abs/10.1021/nn100993t},
year = {2010},
date = {2010-06-08},
journal = {ACS Nano},
volume = {4},
pages = {4017–4026},
note = {Featured on the cover and highlighted in the issue.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Pokroy, Boaz; Kang, Sung Hoon; Mahadevan, L.; Aizenberg, Joanna
Self-Organization of a Mesoscale Bristle into Ordered, Hierarchical Helical Assemblies Journal Article
In: Science, vol. 323, pp. 237-240, 2009, (Highlighted in the issue, and various media including New York Times, NPR, Discovery, AAAS EurekAlert, C&EN, Technology Review, IEEE Spectrum, Science Daily, and New Scientist. ).
@article{Pokroy2009,
title = {Self-Organization of a Mesoscale Bristle into Ordered, Hierarchical Helical Assemblies},
author = {Boaz Pokroy and Sung Hoon Kang and L. Mahadevan and Joanna Aizenberg
},
url = {http://www.sciencemag.org/content/323/5911/237.short},
year = {2009},
date = {2009-01-09},
journal = {Science},
volume = {323},
pages = {237-240},
abstract = {Mesoscale hierarchical helical structures with diverse functions are abundant in nature. Here we show how spontaneous helicity can be induced in a synthetic polymeric nanobristle assembling in an evaporating liquid. We use a simple theoretical model to characterize the geometry, stiffness, and surface properties of the pillars that favor the adhesive self-organization of bundles with pillars wound around each other. The process can be controlled to yield highly ordered helical clusters with a unique structural hierarchy that arises from the sequential assembly of self-similar coiled building blocks over multiple length scales. We demonstrate their function in the context of self-assembly into previously unseen structures with uniform, periodic patterns and controlled handedness and as an efficient particle-trapping and adhesive system. },
note = {Highlighted in the issue, and various media including New York Times, NPR, Discovery, AAAS EurekAlert, C&EN, Technology Review, IEEE Spectrum, Science Daily, and New Scientist. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mandal, Krishna C.; Kang, Sung Hoon; Choi, Michael; Chen, Jian; Zhang, Xi-Cheng; Schleicher, James M.; Schmuttenmaer, Charles A.; Fernelius, Nils C.
III–VI Chalcogenide Semiconductor Crystals for Broadband Tunable THz Sources and Sensors Journal Article
In: IEEE Journal of Selected Topics in Quantum Electronics, vol. 14, pp. 284 – 288, 2008.
@article{Mandal2008,
title = {III–VI Chalcogenide Semiconductor Crystals for Broadband Tunable THz Sources and Sensors},
author = {Krishna C. Mandal and Sung Hoon Kang and Michael Choi and Jian Chen and Xi-Cheng Zhang and James M. Schleicher and Charles A. Schmuttenmaer and Nils C. Fernelius},
url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=4481122},
year = {2008},
date = {2008-04-04},
journal = {IEEE Journal of Selected Topics in Quantum Electronics},
volume = {14},
pages = {284 - 288},
abstract = {The layered chalcogenide semiconductor GaSe has been grown under various crystal growth conditions for optimum performance for tunable terahertz (THz) wave generation and broadband THz detection. Low-temperature photoluminescence (PL), Raman spectroscopy, optical absorption/transmission, electrical charge transport property measurements, and THz time-domain spectroscopy (TDS) have been used to characterize the grown crystals. It is observed that indium doping enhances hardness of the grown GaSe crystals, which is very useful for processing and fabricating large-area devices. GaSe crystals have demonstrated promising characteristics with good optical quality (absorption coefficient les0.1 cm-1 in the spectral range of 0.62-18 mum), high dark resistivity (ges109 Omega cm), wide bandgap (2.01 eV at 300 K), good anisotropic (parand perp) electrical transport properties (mue/h, taue/h, and mutaue/h) and long-term stability. The THz emission measurements have shown that the GaSe crystals are highly efficient for broadband tunable THz sources (up to 40 THz), and sensors (up to 100 THz). Additionally, new THz frequencies (0.1-3 THz) have been observed for the first time from an anisotropic binary and a ternary semiconductor crystal. Details of characterizations as well as optimum crystal growth conditions including simulation and computer modeling are described in this paper.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mandal, Krishna C.; Kang, Sung Hoon; Choi, Michael; Kargar, Alireza; Harrison, Mark J.; McGregor, Douglas S.; Bolotnikov, Aleksey E.; Carini, Gabriella A.; Giuseppe C. Camarda,; James, Ralph B.
Characterization of Low-Defect Cd0.9Zn0.1Te and CdTe Crystals for High-Performance Frisch Collar Detectors Journal Article
In: IEEE Transactions on Nuclear Science, vol. 54, pp. 802 – 806 , 2007.
@article{Mandal2007,
title = {Characterization of Low-Defect Cd0.9Zn0.1Te and CdTe Crystals for High-Performance Frisch Collar Detectors},
author = {Krishna C. Mandal and Sung Hoon Kang and Michael Choi and Alireza Kargar and Mark J. Harrison and Douglas S. McGregor and Aleksey E. Bolotnikov and Gabriella A. Carini and Giuseppe C. Camarda, and Ralph B. James},
url = {http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4291754&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4291754},
year = {2007},
date = {2007-08-20},
journal = {IEEE Transactions on Nuclear Science},
volume = {54},
pages = {802 - 806 },
abstract = {Low dislocation density, high-purity, and low inclusion concentration Cd0.9Zn0.1Te (CZT) and CdTe crystals were grown by a vertical Bridgman technique using in-house zone refined precursors. The grown crystals were sequentially processed using optimized chemo-mechanical processes to fabricate planar and Frisch collar detectors. Infrared transmission and scanning electron microscopy studies have shown that EIC grown CZT and CdTe crystals have significantly lower Te inclusions and defect densities than commercially available spectrometer grade crystals. The charge transport properties (electron and hole mobility-lifetime products, mutaue & mutauh) of various detectors have been evaluated by Hecht analysis. The detectors have been tested for spectral response using 59.5 and 662 keV gamma-ray sources. The CZT detectors with planar electrodes showed 2.6% FWHM at 662 keV. By adding a Frisch collar, the detectors' spectra improved significantly. The Frisch collar detectors proved to be very promising for assembling large-area arrays with excellent energy resolution at relatively low manufacturing cost.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Chen, Jianglong; Leblanc, Valerie; Kang, Sung Hoon; Benning, Paul J.; Schut, David; Baldo, Marc A.; Schmidt, Martin A.; Bulović, Vladimir
High Definition Digital Fabrication of Active Organic Devices by Molecular Jet Printing Journal Article
In: Advanced Functional Materials, vol. 17, pp. 2722–2727, 2007.
@article{Chen2007,
title = {High Definition Digital Fabrication of Active Organic Devices by Molecular Jet Printing},
author = { Jianglong Chen and Valerie Leblanc and Sung Hoon Kang and Paul J. Benning and David Schut and Marc A. Baldo and Martin A. Schmidt and Vladimir Bulović},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adfm.200601144/abstract},
year = {2007},
date = {2007-08-17},
journal = {Advanced Functional Materials},
volume = {17},
pages = {2722–2727},
abstract = {We introduce a high resolution molecular jet (MoJet) printing technique for vacuum deposition of evaporated thin films and apply it to fabrication of 30 μm pixelated (800 ppi) molecular organic light emitting devices (OLEDs) based on aluminum tris(8-hydroxyquinoline) (Alq3) and fabrication of narrow channel (15 μm) organic field effect transistors (OFETs) with pentacene channel and silver contacts. Patterned printing of both organic and metal films is demonstrated, with the operating properties of MoJet-printed OLEDs and OFETs shown to be comparable to the performance of devices fabricated by conventional evaporative deposition through a metal stencil. We show that the MoJet printing technique is reconfigurable for digital fabrication of arbitrary patterns with multiple material sets and high print accuracy (of better than 5 μm), and scalable to fabrication on large area substrates. Analogous to the concept of “drop-on-demand” in Inkjet printing technology, MoJet printing is a “flux-on-demand” process and we show it capable of fabricating multi-layer stacked film structures, as needed for engineered organic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mandal, Krishna C.; Kang, Sung Hoon; Choi, Michael; Wei, Jiuan; Zheng, Lili; Zhang, Hui; Jellison, Gerald E.; Groza, Michael; Burger, Arnold
Component Overpressure Growth and Characterization of High-Resistivity CdTe Crystals for Radiation Detectors Journal Article
In: Journal of Electronic Materials, vol. 36, pp. 1013-1020, 2007.
@article{Mandal2007b,
title = {Component Overpressure Growth and Characterization of High-Resistivity CdTe Crystals for Radiation Detectors},
author = {Krishna C. Mandal and Sung Hoon Kang and Michael Choi and Jiuan Wei and Lili Zheng and Hui Zhang and Gerald E. Jellison and Michael Groza and Arnold Burger },
url = {http://link.springer.com/article/10.1007%2Fs11664-007-0164-y},
year = {2007},
date = {2007-07-06},
journal = {Journal of Electronic Materials},
volume = {36},
pages = {1013-1020},
abstract = {Spectrometer-grade CdTe single crystals with resistivities higher than 109 Ω cm have been grown by the modified Bridgman method using zone-refined precursor materials (Cd and Te) under a Cd overpressure. The grown CdTe crystals had good charge-transport properties (μτ e = 2 × 10−3 cm2 V−1, μτ h = 8 × 10−5 cm2 V−1) and significantly reduced Te precipitates compared with crystals grown without Cd overpressure. The crystal growth conditions for the Bridgman system were optimized by computer modeling and simulation, using modified MASTRAPP program, and applied to crystal diameters of 14 mm (0.55′′), 38 mm (1.5′′), and 76 mm (3′′). Details of the CdTe crystal growth operation, structural, electrical, and optical characterization measurements, detector fabrication, and testing using 241Am (60 keV) and 137Cs (662 keV) sources are presented.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Leblanc, Valerie; Chen, Jianglong; Kang, Sung Hoon; Bulovic, Vladimir; Schmidt, Martin A.
Micromachined Printheads for the Evaporative Patterning of Organic Materials and Metals Journal Article
In: Journal of Microelectromechanical Systems, vol. 16, pp. 394 – 400 , 2007.
@article{Leblanc2007,
title = {Micromachined Printheads for the Evaporative Patterning of Organic Materials and Metals },
author = {Valerie Leblanc and Jianglong Chen and Sung Hoon Kang and Vladimir Bulovic and Martin A. Schmidt},
url = {http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4147590&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F84%2F4147571%2F04147590.pdf%3Farnumber%3D4147590},
year = {2007},
date = {2007-04-10},
journal = {Journal of Microelectromechanical Systems},
volume = {16},
pages = {394 - 400 },
abstract = {This paper describes the design, fabrication, and testing of electrostatically actuated microshutters used as active shadow masks to pattern evaporated materials. The fabricated microshutters can obstruct a 25-mum-wide aperture at an actuation voltage of 90 V, with a resonant frequency of 4 kHz due to a 400-mum-long actuator. The microshutters integrated with an x-y-z manipulator were used to print patterns of organic material and metal on glass substrates in vacuum with a pixel size of 25 mum. The maximum resolution achievable with this setup is 800 dpi, and we printed active organic light-emitting device arrays of 400 dpi resolution. This printing scheme could enable the patterning of large-area organic optoelectronic devices on diverse substrates.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mandal, Krishna C.; Kang, Sung Hoon; Choi, Michael; Bello, Job; Zheng, Lili; Zhang, Hui; Groza, Michael; Roy, Utpal N.; Burger, Arnold; Jellison, Gerald E.; Holcomb, David E.; Wright, Gomez W.; Williams, Joseph A.
Simulation, modeling, and crystal growth of Cd0.9Zn0.1Te for nuclear spectrometers Journal Article
In: Journal of Electronic Materials, vol. 35, pp. 1251-1256, 2006.
@article{Mandal2006,
title = {Simulation, modeling, and crystal growth of Cd0.9Zn0.1Te for nuclear spectrometers},
author = {Krishna C. Mandal and Sung Hoon Kang and Michael Choi and Job Bello and Lili Zheng and Hui Zhang and Michael Groza and Utpal N. Roy and Arnold Burger and Gerald E. Jellison and David E. Holcomb and Gomez W. Wright and Joseph A. Williams },
url = {http://link.springer.com/article/10.1007%2Fs11664-006-0250-6},
year = {2006},
date = {2006-06-01},
journal = {Journal of Electronic Materials},
volume = {35},
pages = {1251-1256},
abstract = {High-quality, large (10 cm long and 2.5 cm diameter), nuclear spectrometer grade Cd0.9Zn0.1Te (CZT) single crystals have been grown by a controlled vertical Bridgman technique using in-house zone refined precursor materials (Cd, Zn, and Te). A state-of-the-art computer model, multizone adaptive scheme for transport and phase-change processes (MASTRAP), is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in the as-grown CZT crystal and optimize the thermal profile. The model accounts for heat transfer in the multiphase system, convection in the melt, and interface dynamics. The grown semi-insulating (SI) CZT crystals have demonstrated promising results for high-resolution room-temperature radiation detectors due to their high dark resistivity (ρ≈2.8 × 1011 Θ cm), good charge-transport properties [electron and hole mobility-life-time product, μτe≈(2–5)×10−3 and μτh≈(3–5)×10−5 respectively, and low cost of production. Spectroscopic ellipsometry and optical transmission measurements were carried out on the grown CZT crystals using two-modulator generalized ellipsometry (2-MGE). The refractive index n and extinction coefficient k were determined by mathematically eliminating the ∼3-nm surface roughness layer. Nuclear detection measurements on the single-element CZT detectors with 241Am and 137Cs clearly detected 59.6 and 662 keV energies with energy resolution (FWHM) of 2.4 keV (4.0%) and 9.2 keV (1.4%), respectively.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kang, Sung Hoon; Crisp, Todd; Kymissis, Ioannis; Bulović, Vladimir
Memory Effect from Charge Trapping in Layered Organic Structures Journal Article
In: Applied Physics Letters, vol. 85, pp. 4666-4668, 2004.
@article{Kang2004,
title = {Memory Effect from Charge Trapping in Layered Organic Structures},
author = {Sung Hoon Kang and Todd Crisp and Ioannis Kymissis and Vladimir Bulović},
url = {http://scitation.aip.org/content/aip/journal/apl/85/20/10.1063/1.1819991},
year = {2004},
date = {2004-11-15},
journal = {Applied Physics Letters},
volume = {85},
pages = {4666-4668},
abstract = {We demonstrate organic light emitting devices(OLEDs) with a charge trap layer that show memory behavior. These OLEDs demonstrate that organic heterojunction structures can controllably trap and release electronic charges. The trap layer is either 5-nm-thick clustered silver islands, or a 10-nm-thick organic laser dye DCM2 ([2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)-ethenyl]-4H-pyran-4-ylidene] propane-dinitrile) doped into TPD (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine). Predictions of the energy band structure indicate that both DCM2 sites and the metal islands can trap charge, consistent with the measured current–voltage characteristics. Trap sites are charged by applying reverse bias over the OLEDs. For devices with DCM2 traps we observe quenching of DCM2 photoluminescence upon charging, which allows us to quantify the charged trap density as approximately 10% of the trap sites or 10^18cm^−3. From time resolved measurements we observe that the charge retention time exceeds 2h.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Eisape, Adebayo; Sun, Bohan; Li, Jing; Kang, Sung
Nanoporous Composite Sensors Book Chapter
In: pp. 85-109, 0000, ISBN: 978-3-030-81826-5.
@inbook{nokey,
title = {Nanoporous Composite Sensors},
author = {Eisape, Adebayo and Sun, Bohan and Li, Jing and Kang, Sung},
url = {10.1007/978-3-030-81827-2_5},
isbn = {978-3-030-81826-5},
pages = {85-109},
keywords = {},
pubstate = {published},
tppubtype = {inbook}
}
Note: Send e-mail to Prof. Kang at [email protected] if you need a pdf file of the papers below.
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