Minshi An

University of Incheon, Seoul, Seoul, South Korea

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Publications (7)4.69 Total impact

  • Minshi An, Jong-Dal Hong
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    ABSTRACT: In this paper, we describe organic surface modification and functionalization of a hafnia substrate, which has been extensively investigated as a replacement of the gate insulting SiO2 layer in field effect transistors. The surface state of the hafnia was assessed by water contact angle (θwater) measurement with comparison to that of the silicone during the layer-by-layer (LBL) deposition of poly(allyamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) bilayers by means of the spin-coating electrostatic self-assembly, SCESA, method. The surface state of virgin hafnia (θwater = 73 ± 1°) turned hydrophilic (θwater = 8 ± 2°) after submission to the standard RCA cleaning process of silicon. The thickness of the multilayer films on the cleaned hafnia surface was found to grow linearly with an increase in the number of PAH/PSS bilayers (d = 2.2 ± 0.1 nm), indicating the consistency in the formation of uniform films. The average water contact angle of the PAH and PSS layers on hafnia alternately switched between 36.0 ± 0.7° and 29.7 ± 0.4° during the nine deposition cycles. The analysis of the surface topography by means of atomic force microscopy (AFM) indicated that the surface roughness of the first PAH layer deposited on the hafnia was strongly smoothed from 1.54 to 0.44 nm with increasing the LBL deposition of polyelectrolytes.
    Colloids and Surfaces A: Physicochemical and Engineering Aspects. 01/2009;
  • Minshi An, Jong-Dal Hong
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    ABSTRACT: This paper describes a new strategy for maximizing the density limit of Pd nanoparticle (∼4nm) monolayers (∼1.6×1012particles/cm2). These were obtained on a flat silicone substrate by means of the spin-coating electrostatic self-assembly method. The density limit probably originated from electrostatic repulsion among identically charged nanoparticles in solution and on the substrate. The ester-modified Pd nanoparticles (NPs) (D≈4nm) spin-coated on amino-functionalized silicon are directly immobilized on the substrate through hydrogen bonding during acidic hydrolysis. Using this method, the particle density increased more than three times, to 4.69×1012particles/cm2, compared with previous results that were obtained by using electrostatic attraction.
    Colloids and Surfaces A-physicochemical and Engineering Aspects - COLLOID SURFACE A. 01/2009; 336(1):8-11.
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    ABSTRACT: Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates. We present both metal (Pd) and semiconductor (CdSe) nanocrystals arrayed in monolayer onto trenched silicon wafers (4 inch diameter) using a facile electrostatic adsorption scheme. In particular, CdSe nanocrystal arrays in the trench well showed superior luminescent efficiency compared to those onto the protruded trench flat, due to the densely arrayed CdSe nanocrystals in the vertical direction. Furthermore, the surface coverage controllability was investigated using a 2D silicon substrate. Our approach can be applied to generate highly efficient displays, memory chips and integrated sensing devices.
    Journal of Nanoscience and Nanotechnology 01/2008; 7(12):4285-93. · 1.15 Impact Factor
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    ABSTRACT: Spin-coating electrostatic self-assembly (SCESA) is utilized to fabricate a single layer of carboxylic-acid-coated Pd nanoparticles (NPs) (D??5 nm) on an oppositely charged surface. The packing density of a NP monolayer formed on a rotating solid substrate (3000 rpm) was examined with regards to various parameters, including the particle concentration, the pH, and the ionic strength of the solution. Initially, the packing density grew exponentially with increases in the particle concentration, up to a maximum value (of 8.4 ´ 1011/cm2) at 1.2 wt%. The packing density was also found to increase drastically as the pH decreased and the ionic strength of the solution increased; these trends can be attributed to a reduction in the interparticle repulsions among the NPs in the solution and on the substrate. The best result of this study was achieved in a 1.2 wt% solution at pH 8; under these conditions, an NP monolayer with the highest density (namely, 1.6 ´ 1012/cm2) was obtained.
    Bulletin- Korean Chemical Society 01/2008; 29(3). · 0.84 Impact Factor
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    ABSTRACT: Monolayer arrays of monodispersed nanocrystals onto three-dimensional substrates have considerable potential for various engineering applications due to their highly integrated features with nanocrystal homogeneity. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto three-dimensional substrates. We present nanocrystal Pd metal arrayed in monolayers onto trenched silicon wafers (4 in. diam) using a facile electrostatic adsorption scheme. We also present three-dimensional electron tomography bright-field projection images, which reveal that the resulting arrays of Pd nanocrystals indeed have the monolayer nature on the overall trenched wafer surface and are not affected by trench geometry.
    Journal of The Electrochemical Society. 02/2007; 154(3):H202-H204.
  • Minshi An, Jong-Dal Hong
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    ABSTRACT: The recently established spin-coating electrostatic self-assembly (SCESA) technique has been shown to facilitate not only the rapid fabrication of polyelectrolyte multilayer assemblies, but also allow each layer to be easily controlled on a monomolecular scale by minimizing the film thickness across a substrate surface. In this paper, the influence of polyelectrolyte concentration on the amount and thickness of spin-deposited polymer films has been examined for a multilayer system of poly(allyamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS), when the washing steps employed for removing weakly bound polyelectrolytes on a resultant film on a substrate are excluded from the standard fabrication procedure of the SCESA method. The thickness of the spin-deposited PAH/PSS bilayer increased linearly for the PSS concentrations in the range from 1 to 10 mM with PAH constant at 1 mM, which demonstrates the uniform deposition of each layer material onto the thin film. The thickness of PAH/PSS bilayers increased from 1.43±0.06 to 3.37±0.08 nm as the PSS concentration increased from 1 to 10 mM, while the PAH concentration was kept constant at 1 mM. The multilayer films were found to be stable in a good solvent (H2O) for at least 30 h, without any noticeable loss of the adsorbed layer component of the polyelectrolyte. This improvement to the SCESA method (exclusion of washing steps) provides a convenient way to create multilayer heterostructures with the thickness of each layer being easily adjusted.
    Thin Solid Films 01/2006; 500(1):74-77. · 1.87 Impact Factor
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    Bulletin- Korean Chemical Society 01/2006; 27(8). · 0.84 Impact Factor