• Korean Journal of Materials Research
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• v.31 no.7
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• pp.420-426
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• 2021

Graphene, a new material with various advantageous properties, has been actively used in various fields in recent years. Applications of graphene oxide are increasing in combination with other materials due to the different properties of graphene oxide, depending on the number of single and multiple layers of graphene. In this study, single-layer graphene oxide and multi-layer graphene oxide are spray coated on polystyrene, and the physicochemical properties of the coated surfaces are characterized using SEM, Raman spectroscopy, AFM, UV-Vis spectrophotometry, and contact angle measurements. In single-layer graphene oxide, particles of 20 ㎛ are observed, whereas a 2D peak is less often observed, and the difference in surface height increases according to the amount of graphene oxide. Adhesion increases with an increase in graphene oxide up to 0.375 mg, but decreases at 0.75 mg. In multi-layer graphene oxide, particles of 5 ㎛ are observed, as well as a 2D peak. According to the amount of graphene oxide, the height difference of the surface increases and the adhesive strength decreases. Both materials are hydrophilic, but single-layer graphene oxide has a hydrophilicity higher than that of multi-layer graphene oxide. We believe that multi-layer graphene oxide and single-layer graphene oxide can be implemented based on the characteristics that make them suitable for application.

• YAKHAK HOEJI
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• v.30 no.1
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• pp.42-46
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• 1986

The binding characteristics of five cephalosporins, cefamandole, ceftriaxone, cefoxitin, latamoxef, and cefotetan to bovine serum albumin (BSA) was examined by UV difference spectrophotometry. 2-(4'-hydroxybenzeneazo) benzoic acid was used as the spectrophotometric probe. Competitive bindings between the probe and cephalosporins were observed. Based on the Scatchard plot, the BSA appeared to have two classes of binding sites in BSA binding with cephalosporins. The number of primary binding sites appears to be one, secondary binding sites appears to be three. The binding constants were found as follows: BSA-HBAB; $K_1^{obs}$=8.39$\times$$10^4$ $M^{-1}$, $K_2^{obs}$=1.60$\times$$10^4$ $M^{-1}$, BSA-Cefamandole; $K_1^{obs}$=5.44$\times$$10^3$ $M^{-1}$, $K_2^{obs}$=0.74$\times$$10^3$ $M^{-1}$, BSA-Cefotriaxone; $K_1^{obs}$=6.78$\times$$10^3$ $M^{-1}$, $K_2^{obs}$=0.88$\times$$10^3$ $M^{-1}$, BSA-Cefoxitin; $K_1^{obs}$=7.24$\times$$10^3$ $M^{-1}$, $K_2^{obs}$=1.13$\times$$10^3$ $M^{-1}$, BSA-Latamoxef; $K_1^{obs}$=8.87$\times$$10^3$ $M^{-1}$, $K_2^{obs}$=1.92$\times$$10^3$ $M^{-1}$, BSA-Cefotetan; $K_1^{obs}$=15.41$\times$$10^3$ $M^{-1}$, $K_2^{obs}$=2.7$\times$$10^3$ $M^{-1}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.376-381
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• 2019

In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.