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Hierarchical multi-level block copolymer patterns by multiple self-assembly
Jung, Hyunsung,Shin, Won Ho,Park, Tae Wan,Choi, Young Joong,Yoon, Young Joon,Park, Sung Heum,Lim, Jae-Hong,Kwon, Jung-Dae,Lee, Jung Woo,Kwon, Se-Hun,Seong, Gi Hun,Kim, Kwang Ho,Park, Woon Ik The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.17
<P>Uniform, well-ordered sub-20 nm patterns can be generated by the templated self-assembly of block copolymers (BCPs) with a high Flory-Huggins interaction parameter (<I>χ</I>). However, the self-assembled BCP monolayers remain limited in the possible structural geometries. Here, we introduce a multiple self-assembly method which uses di-BCPs to produce diverse morphologies, such as dot, dot-in-honeycomb, line-on-dot, double-dot, pondering, dot-in-pondering, and line-on-pondering patterns. To improve the diversity of BCP morphological structures, we employed sphere-forming and cylinder-forming poly(styrene-<I>block</I>-dimethylsiloxane) (PS-<I>b</I>-PDMS) BCPs with a high <I>χ</I>. The self-assembled mono-layer and double-layer SiOx dot patterns were modified at a high temperature (∼800 °C), showing hexagonally arranged (dot) and double-hexagonally arranged (pondering) SiOx patterns, respectively. We successfully obtained additional new nanostructures (big-dot, dot-in-honeycomb, line-on-dot, pondering, dot-in-pondering, and line-on-pondering types) through a second self-assembly of cylinder-forming BCPs using the dot and pondering patterns as guiding templates. This simple approach can likely be extended to the multiple self-assembly of many other BCPs with good functionality, significantly contributing to the development of various nanodevices.</P>
Jung, Hyunsung,Rheem, Youngwoo,Chartuprayoon, Nicha,Lim, Jae-Hong,Lee, Kyu-Hwan,Yoo, Bongyoung,Lee, Kun-Jae,Choa, Yong-Ho,Wei, Peng,Shi, Jing,Myung, Nosang V. Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.44
<P>We demonstrated the wafer level batch synthesis and fabrication of single semiconducting thermoelectric nanoribbon based devices by Lithographically Patterned Galvanic Displacement (LPGD). The shape, composition, and dimension of nanoribbons were tailored by adjusting deposition conditions. High resolution TEM images with fast Fourier transform (FFT)-converted selected area electron diffraction (SAED) patterns confirmed the formation of polycrystalline Bi<SUB>2</SUB>Te<SUB>3</SUB> intermetallic compound with a rhombohedral structure without elemental Te and Bi. The thickness dependent electrical resistivity of Bi<SUB><I>x</I></SUB>Te<SUB><I>y</I></SUB> nanoribbons shows a classic size effect due to the increase in surface boundary scattering. The as-synthesized nanoribbons were n-type semiconductors with no clear trend between field effect carrier mobility and composition, which might be attributed to the trapped charges at the interface between the channel and dielectric layer. The preliminary results on thermoelectric properties (<I>i.e.</I> Seebeck coefficient and power factor) show that the Seebeck coefficient of as-synthesized 0.1 µm thick Bi<SUB>30</SUB>Te<SUB>70</SUB> nanoribbon is comparable with bulk counterparts, however, the power factor was lower because of poor crystallinity which leads to higher resistivity.</P> <P>Graphic Abstract</P><P>Wafer-scale synthesis of single semiconducting BiTe nanoribbons was demonstrated by Lithographically Patterned Galvanic Displacement with controlled composition and dimensions. Composition and size dependent material, electrical, and thermoelectrical properties were systematically investigated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm02058c'> </P>
Logic Operations Based on Magnetic-Vortex-State Networks
Jung, Hyunsung,Choi, Youn-Seok,Lee, Ki-Suk,Han, Dong-Soo,Yu, Young-Sang,Im, Mi-Young,Fischer, Peter,Kim, Sang-Koog American Chemical Society 2012 ACS NANO Vol.6 No.5
<P>Logic operations based on coupled magnetic vortices were experimentally demonstrated. We utilized a simple chain structure consisting of three physically separated but dipolar-coupled vortex-state Permalloy disks as well as two electrodes for application of the logical inputs. We directly monitored the vortex gyrations in the middle disk, as the logical output, by time-resolved full-field soft X-ray microscopy measurements. By manipulating the relative polarization configurations of both end disks, two different logic operations are programmable: the XOR operation for the parallel polarization and the OR operation for the antiparallel polarization. This work paves the way for new-type programmable logic gates based on the coupled vortex-gyration dynamics achievable in vortex-state networks. The advantages are as follows: a low-power input signal by means of resonant vortex excitation, low-energy dissipation during signal transportation by selection of low-damping materials, and a simple patterned-array structure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-5/nn3000143/production/images/medium/nn-2012-000143_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3000143'>ACS Electronic Supporting Info</A></P>
One-Pot Process in Scalable Bath for Water-Dispersed ZnS Nanocrystals with the Tailored Size
Jung, Hyunsung,Phelps, Tommy J.,Rondinone, Adam J.,Jellison, Gerald E.,Duty, Chad E.,Han, Kee Sung,Moon, Ji-Won American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.5
<P>Well-dispersed ZnS nanocrystals with tailored size in aqueous solutions were synthesized by employing cysteine-sulfur (Cys-S) complexes with low molecular weight in a scalable anoxic vessel. High yield production of water-dispersed ZnS nanocrystals on a 10-L scale was demonstrated in an aqueous solution process. The average crystallite size of ZnS was controlled by changing the ratio of the cysteine to sulfide in the applied Cys-S complexes. A decrease in the crystallite size of ZnS likely resulted in both the blue shift of peak positions and the relative variation of peak intensities in the photoluminescence properties. Additionally, the pH-dependent stability against aggregation of ZnS nanocrystals was investigated to reduce agglomeration.</P>