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Si Nae Heo,Keun Young Park,Yong Jun Seo,Faheem Ahmed,M. S. Anwar,구본흔 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3
In this research, ZnO nanorods have been successfully synthesized via wet chemical method. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO nanorods. By only varying the concentration of Hexamethylenetetramine (HMT) in the solution, morphology of ZnO changed from hexagonal facet nanorods to pencil like nanorods and size of nanorods also changed. The band gap of as-synthesized ZnO nanorods was found to increase with increasing the concentration of HMT in the solution. The narrow full-width at half-maximum (FWHM) of the UV emission of PL spectra indicated that the grown ZnO nanorods have high crystal quality and is well matched with the obtained XRD results. These results revealed that the concentration of Hexamethylenetetramine plays a vital role to control the properties of ZnO nanorods.
Han, Si-Nae,Oh, Poo-Reum,Kim, Hong-Sig,Heo, Hwa-Young,Moon, Jun-Cheol,Lee, Sang-Kyu,Kim, Kyung-Hee,Seo, Yong-Weon,Lee, Byung-Moo The Korean Society of Crop Science 2007 Journal of crop science and biotechnology Vol.10 No.2
Antibiotics used for suppressing Agrobacterium in plant transformation procedure might have negligible effects on plant tissues and regeneration. The effects of antibiotics on growth suppression of Agrobacterium and plant regeneration were investigated for enhancing Agrobacterium-mediated transformation using wheat mature embryos. Antibiotics tested, except carbenicillin, were able to suppress that embryos were coated with a layer of Agrobacterium cells in callus induction medium. Agrobacterium growth was suppressed minimally at 50 mg/l of timentin, while cefotaxime and clavamox were completely suppressed at relative high concentration of 250 mg/l. In the treatment of carbenicillin, initiation of growth suppression of Agrobacterium occurred at 750 mg/l of concentration because Agrobacterium KYRT1 contains the carbenicillin resistant gene. In Agrobacterium inoculation, effects of antibiotics were significantly different on the rate of callus induction and shoot formation. Almost embryos were induced calli at 50 mg/l of timentin whereas callus induction rate was achieved above 90% at 100 mg/l and 250 mg/l of cefotaxime and clavamox, respectively. Shoot formation rate was higher in the treatment of timentin than that of cefotaxime and clavamox at 500 mg/l of concentration, respectively. Timentin can be used as a good antibiotics in Agrobacterium-mediated wheat transformation.
Vertically Aligned ZnO Nanorods: Effect of Synthesis Parameters
Rehman, Zeeshan Ur,Heo, Si-Nae,Cho, Hyeon Ji,Koo, Bon Heun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6
<P>This report is devoted to the synthesis of high quality nanorods using spin coating technique for seed layer growth. Effect of different parameter i.e., spins coating counts, spin coating speed, and the effect of temperature during the drying process was analyzed. Hot plate and furnace technique was used for heating purpose and the difference in the morphology was carefully observed. It is worthy to mention here that there is a substantial effect of all the above mentioned parameters on the growth and morphology of the ZnO nanostructure. The ZnO nanorods were finally synthesized using wet chemical method. The morphological properties of the obtained nanostructures were analyzed by using FESEM technique.</P>
Ta Doped SnO<sub>2</sub> Transparent Conducting Films Prepared by PLD
Cho, Ho Je,Seo, Yong Jun,Kim, Geun Woo,Park, Keun Young,Heo, Si Nae,Koo, Bon Heun Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.8
Transparent and conducting thin films of Ta-doped $SnO_2$ were fabricated on a glass substrate by a pulse laser deposition(PLD) method. The structural, optical, and electrical properties of these films were investigated as a function of doping level, oxygen partial pressure, substrate temperature, and film thickness. XRD results revealed that all the deposited films were polycrystalline and the intensity of the (211) plane of $SnO_2$ decreased with an increase of Ta content. However, the orientation of the films changed from (211) to (110) with an increase in oxygen partial pressure (40 to 100 mTorr) and substrate temperature. The crystallinity of the films also increased with the substrate temperature. The electrical resistivity measurements showed that the resistivity of the films decreased with an increase in Ta doping, which exhibited the lowest resistivity (${\rho}{\sim}1.1{\times}10^{-3}{\Omega}{\cdot}cm$) for 10 wt% Ta-doped $SnO_2$ film, and then increased further. However, the resistivity continuously decreased with the oxygen partial pressure and substrate temperature. The optical bandgap of the 10 wt% Ta-doped $SnO_2$ film increased (3.67 to 3.78 eV) with an increase in film thickness from 100-700 nm, and the figure of merit revealed an increasing trend with the film thickness.
Magnetic, Optical and Structural Property Studies of Mn-Doped ZnO Nanosheets
Ahmed, Faheem,Kumar, Shalendra,Arshi, Nishat,Anwar, M. S.,Kim, Geun Woo,Heo, Si Nae,Byon, Eung Sun,Lee, Sung Hun,Lyu, Nam Jin,Koo, Bon Heun American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>We report the synthesis of pure and Mn doped ZnO in the form of nanosheets using a simple and single step procedure involving a microwave assisted chemical method. As prepared Mn-doped ZnO nanosheets were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible (UV-Vis), Raman spectroscopy and magnetization measurements. The structural studies using XRD and TEM revealed the absence of Mn-related secondary phases and showed that Mn-doped ZnO comprise a single phase nature with wurtzite structure. FESEM and TEM micrographs show that the average diameter of Mn-ZnO assembled nanosheets is about approximately 50 nm, and the length of a Mn-doped ZnO nanosheet building block which is made up of thin mutilayered sheets is around approximately 300 nm. Concerning the Raman scattering spectra, the shift in peak position of E2 (high) mode toward low frequencies due to the Mn doping could be explained well by means of the spatial correlation model. Magnetic measurements showed that Mn-doped ZnO nanosheets exhibit ferromagnetic ordering at or above room temperature.</P>
Electrical and Optical Properties of Ga-doped SnO₂ Thin Films Via Pulsed Laser Deposition
Chang Hoon Sung,Geun Woo Kim,Yong Jun Seo,Si Nae Heo,Seok Hwan Huh,Ji Ho Chang,Bon Heun Koo 한국표면공학회 2011 한국표면공학회지 Vol.44 No.4
Ga₂O₃-doped SnO₂ thin films were grown by using pulsed laser deposition (PLD) technique on glass substrate. The optical and electrical properties of these films were investigated for different doping concentrations, oxygen partial pressures, substrate temperatures, and film thickness. The films were deposited at different substrate temperatures (room temperature to 600℃). The best opto-electrical properties is shown by the film deposited at substrate temperature of 300℃ with oxygen partial pressure of 80 m Torr and the gallium concentration of 2 wt%. The as obtained lowest resistivity is 9.57 × 10?³ Ω ㎝ with the average transmission of 80% in the visible region and an optical band gap (indirect allowed) of 4.26 eV.
Al<sup>3+</sup>와 Y<sup>3+</sup> 동시치환 SnO<sub>2</sub> 투명전극 박막의 전기적 특성
김근우,서용준,성창훈,박근영,조호제,허시내,구본흔,Kim, Geun-Woo,Seo, Yong-Jun,Sung, Chang-Hoon,Park, Keun-Young,Cho, Ho-Je,Heo, Si-Nae,Koo, Bon-Heun 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.10
Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.