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Yun Y.J.,Korea Research Institute of Chemical Technology | Wu M.,Korea Research Institute of Chemical Technology | Kim J.K.,Korea Research Institute of Chemical Technology | Ju J.Y.,Korea Research Institute of Chemical Technology | And 8 more authors.
Journal of Nanomaterials | Year: 2015

The electrochemical performance of Li(Mn, M)PO(M = Co2+/3+, Ni2+/3+) was investigated with regard to the particle morphology. Within a controlled chemical composition, Li(MnoiPO the resultant cathode exhibited somewhat spherical-shaped nanocrystalline particles and enhanced Li+-ion storage, which was even better than the undoped LiMnPO up to 16% in discharge capacity at 0.05 C. The outstanding electrochemical performance is attributed to the well-dispersed spherical-shaped particle morphology, which allows the fast Li+-ion migration during the electrochemical lithiation/delithiation process, especially at high current density. © 2015 Young Jun Yun et al.

Kim M.J.,Pusan National University | Park W.I.,Global Frontier Randnter for Hybrid Interface Materials | Choi Y.J.,Pusan National University | Jung Y.K.,Ulsan National Institute of Science and Technology | And 2 more authors.
RSC Advances | Year: 2016

The directed self-assembly (DSA) of block copolymers (BCPs) has attracted considerable attention due to the outstanding ability of this method to complement or replace the conventional photolithography process. However, there are critical issues to resolve in order to realize the rapid pattern formation of BCPs with a high Flory-Huggins parameter (χ). Here, we introduce a simple method to expedite the self-assembly kinetics with the addition of a polystyrene homopolymer (hPS) to poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) BCPs with a high-χ parameter. We provide a systematic presentation of how the hPS affects the self-assembly of PS-b-PDMS BCPs in the immersion annealing process. We found the optimum annealing conditions of the mixing ratio for the hPS/PS-b-PDMS BCP blends, showing a very short annealing time (<1 min) to obtain highly-ordered nanostructures. In addition, we discuss how the annealing temperature and mixing ratio of the binary solvent improve the self-assembly kinetics of the hPS/PS-b-PDMS BCP blends, suggesting a new route which effectively enhances the self-assembly speed. We believe that this facile and useful approach is applicable to the other BCP combination studies, contributing to the development of the next-generation BCP lithography. © The Royal Society of Chemistry 2016.

Park W.I.,Korea Advanced Institute of Science and Technology | Park W.I.,Global Frontier Randnter for Hybrid Interface Materials | Kim J.M.,Korea Advanced Institute of Science and Technology | Jeong J.W.,Korea Advanced Institute of Science and Technology | And 8 more authors.
Chemistry of Materials | Year: 2015

Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. However, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. In this study, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge2Sb2Te5) and a heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2-3 μA. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. This approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances. © 2015 American Chemical Society.

Park W.I.,Global Frontier Randnter for Hybrid Interface Materials | Choi Y.J.,Pusan National University | Yun J.M.,Global Frontier Randnter for Hybrid Interface Materials | Hong S.W.,Pusan National University | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2015

The rapid pattern formation of well-ordered block copolymer (BCP) nanostructures is practical for next-generation nanolithography applications. However, there remain critical hurdles to achieve the rapid self-assembly of BCPs with a high Flory-Huggins interaction parameter (x), owing to their slow kinetics. In this article, we report that a binary solvent vapor annealing methodology can significantly accelerate the self-assembly kinetics of poly(dimethylsiloxane-b-styrene) (PDMS-b-PS) BCPs with a high-x. In particular, we systemically analyzed the effects of the mixing ratio of a binary solvent composed of a PDMS-selective solvent (heptane) and a PS-selective solvent (toluene), showing an ultrafast self-assembly time (≤1 min) to obtain a well-ordered nanostructure. Moreover, we successfully accomplished extremely fast generation of sub-20 nm dot patterns within an annealing time of 10 s in a 300 nm-wide trench by means of binary solvent annealing. We believe that these results are also applicable to other solvent-based annealing systems of BCPs and that they will contribute to the realization of next-generation ultrafine lithography applications. © 2015 American Chemical Society.

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