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Ulsan, South Korea

Eom T.,Seoul National University | Gwon T.,Seoul National University | Yoo S.,Seoul National University | Choi B.J.,Seoul National University of Science and Technology | And 6 more authors.
Journal of Materials Chemistry C | Year: 2015

The chemical interaction between the [(CH3)3Si]3Sb precursor and atomic layer deposited Sb2Te3 thin films was examined at temperatures ranging from 70 to 220 °C. The trimethylsilyl group [(CH3)3Si] displays greater affinity for Te than for Sb, and this drives replacement of Te in the film with Sb from the [(CH3)3Si]3Sb precursor, while eliminating volatile [(CH3)3Si]2Te, especially at elevated temperatures. The compositions of the resulting Sb-Te layers lie on the Sb2Te3-Sb tie line. The incorporation behavior of [(CH3)3Si]3Sb was explained in terms of a Lewis acid-base reaction. The exchange reactions occurred to relieve the unfavorable hard-soft Lewis acid-base pair between the trimethylsilyl group and Sb in [(CH3)3Si]3Sb. Such a reaction could be usefully adopted to control the chemical composition of ternary Ge-Sb-Te thin films. This journal is © The Royal Society of Chemistry 2015. Source


Eom T.,Seoul National University | Gwon T.,Seoul National University | Yoo S.,Seoul National University | Choi B.J.,Seoul National University of Science and Technology | And 4 more authors.
Chemistry of Materials | Year: 2014

(GeTe2)(1-x)(Sb2Te3) x (GST) layers were deposited via atomic layer deposition (ALD) at growth temperatures ranging from 50 to 120 C using Ge(OCH3) 4 or Ge(OC2H5)4, Sb(OC 2H5)3, and [(CH3) 3Si]2Te as the metal-organic precursors of the Ge, Sb, and Te elements, respectively. The GST layers with compositions lying on the GeTe2-Sb2Te3 tie lines could be obtained by varying the ratio of the Ge-Te and Sb-Te ALD cycles. Although the incorporation of an Sb-Te layer into the GST film occurred in a genuine ALD manner, that of the Ge-Te layer was governed by the kinetically limited physisorption of Ge precursors. The incorporation behavior of the Ge precursor with different ligands was explained by the adsorption and desorption kinetics based on the Brunauer-Emmett-Teller isotherm. The ALD-like film growth behavior could be well-explained by the kinetically limited incorporation of Ge atoms. © 2014 American Chemical Society. Source


Mutlu A.,University of Ulsan | Lee B.-K.,University of Ulsan | Lee C.-H.,University of Ulsan | Kim J.-Y.,Air Products Korea Inc.
Journal of Cleaner Production | Year: 2012

The handling of generated sludge waste during polymer production is one of the main environmental concerns of the polymer industry. An alternative filtration technique was applied to determine the efficiency of different types of filtering media for polymer production. A vibration filter media was replaced with a non-woven fabric filter that was previously used in the refining facility. The purpose of this study is to analyze how much the new filtration affects sludge generation and final production. The application of these alternative filtration techniques have resulted in a significant reduction in the amount of non-recyclable sludge by approximately 77%, while the total amount of polymer production has increased by 41% during the six-year study period. The refining facility saved a total of 617,710 USD/y by changing the filtration system, resulting in an increase in product recovery and a decrease in sludge generation, as well as an improvement in reaction conditions. © 2011 Elsevier Ltd. All rights reserved. Source


Eom T.,Seoul National University | Gwon T.,Seoul National University | Yoo S.,Seoul National University | Choi B.J.,Seoul National University of Science and Technology | And 5 more authors.
Chemistry of Materials | Year: 2015

For phase change memories application, Ge-Sb-Te films were prepared by a stable and reliable atomic layer deposition (ALD) method. Ge(OC2H5)4, Sb(OC2H5)3, [(CH3)3Si]3Sb, and [(CH3)3Si]2Te were used to deposit various layers with compositions that can be described by combinations of GeTe2-Sb2Te layers including Ge2Sb2Te5 at a substrate temperature as low as 70 °C. A shift in composition of Sb-Te films from Sb2Te3 to Sb2Te composition was achieved by combining ligand exchange and substitution reaction between Sb in [(CH3)3Si]3Sb and Te in the Sb2Te3 layer. This surface-limited ALD process allowed highly conformal, smooth, and reproducible film growth over a contact hole structure, highlighting the feasibility of phase change memory applications. © 2015 American Chemical Society. Source


Eom T.,Seoul National University | Choi S.,Seoul National University | Choi B.J.,Seoul National University | Lee M.H.,University of California at Merced | And 8 more authors.
Chemistry of Materials | Year: 2012

Phase change random access memory appears to be the strongest candidate for next-generation high density nonvolatile memory. The fabrication of ultrahigh density phase change memory (≫1 Gb) depends heavily on the thin film growth technique for the phase changing chalcogenide material, most typically containing Ge, Sb and Te (Ge-Sb-Te). Atomic layer deposition (ALD) at low temperatures is the most preferred growth method for depositing such complex materials over surfaces possessing extreme topology. In this study, [(CH 3) 3Si] 2Te and stable alkoxy-Ge (Ge(OCH 3) 4) and alkoxy-Sb (Sb(OC 2H 5) 3) metal-organic precursors were used to deposit various layers with compositions lying on the GeTe 2-Sb 2Te 3 tie lines at a substrate temperature as low as 70 °C using a thermal ALD process. The adsorption of Ge precursor was proven to be a physisorption type while other precursors showed a chemisorption behavior. However, the adsorption of Ge precursor was still self-regulated, and the facile ALD of the pseudobinary solid solutions with composition (GeTe 2) (1-x)(Sb 2Te 3) x were achieved. This chemistry-specific ALD process was quite robust against process variations, allowing highly conformal, smooth, and reproducible film growth over a contact hole structure with an extreme geometry. The detailed ALD behavior of binary compounds and incorporation behaviors of the binary compounds in pseudobinary solid solutions were studied in detail. This new composition material showed reliable phase change and accompanying resistance switching behavior, which were slightly better than the standard Ge 2Sb 2Te 5 material in the nanoscale. The local chemical environment was similar to that of conventional Ge 2Sb 2Te 5 materials. © 2012 American Chemical Society. Source

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