• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.111.2-111.2
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• 2015

Typical electrodes (metal or indium tin oxide (ITO)), which were used in conventional organic light emitting devices (OLEDs) structure, have transparency and conductivity, but, it is not suitable as the electrode of the flexible OLEDs (f-OLEDs) due to its brittle property. Although Graphene is the most well-known alternative material for conventional electrode because of present electrode properties as well as flexibility, its carrier injection barrier is comparatively high to use as electrode. In this work, we performed plasma treatment on the graphene surface and alkali metal doping in the organic materials to study for its possibility as anode and cathode, respectively. By using Ultraviolet Photoemission Spectroscopy (UPS), we investigated the interfaces of modified graphene. The plasma treatment is generated by various gas types such as O2 and Ar, to increase the work function of the graphene film. Also, for co-deposition of organic film to do alkali metal doping, we used three different organic materials which are BMPYPB (1,3-Bis(3,5-di-pyrid-3-yl-phenyl)benzene), TMPYPB (1,3,5-Tri[(3-pyridyl)-phen-3-yl]benzene), and 3TPYMB (Tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane)). They are well known for ETL materials in OLEDs. From these results, we found that graphene work function can be tuned to overcome the weakness of graphene induced carrier injection barrier, when the interface was treated with plasma (alkali metal) through the value of hole (electron) injection barrier is reduced about 1 eV.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.164-164
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• 2013

Among multicomponent nanostructures, hybrid nanocatalysts consisting of metal nanoparticle-semiconductor junctions offer an interesting platform to study the role of metal-oxide interfaces and hot electron flows in heterogeneous catalysis. In this study, we report that hot carriers generated upon photon absorption significantly impact the catalytic activity of CO oxidation. We found that Pt-CdSe-Pt nanodumbbells exhibited a higher turnover frequency by a factor of two during irradiation by light with energy higher than the bandgap of CdSe, while the turnover rate on bare Pt nanoparticles didn't depend on light irradiation. We also found that Pt nanoparticles deposited on a GaN substrate under light irradiation exhibit changes in catalytic activity of CO oxidation that depends on the type of doping of the GaN. We suppose that hot electrons are generated upon the absorption of photons by the semiconducting nanorods or substrates, whereafter the hot electrons are injected into the Pt nanoparticles, resulting in the change in catalytic activity. We discuss the possible mechanism for how hot carrier flows generated during light irradiation affect the catalytic activity of CO oxidation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.142.2-142.2
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• 2013

The effect of substrate on catalytic activity of CO oxidation with transition metal Platinum nanoparticles on doped and undoped TiO2 was investigated. Titanium dioxide was doped chemically with non-metal anions including nitrogen and fluorine. Undoped TiO2 was synthesized via simple conventional sol-gel route. Thin films of titania were developed by spin coating technique and the characterization techniques SEM, XRD, UV-Vis Absorption Spectroscopy and XPS were carried out to examine the morphology of films, crystal phase, crystallites, optical properties and elemental composition respectively. XPS analysis from doped TiO2 confirmed that the nitrogen site were interstitial whereas fluorine was doped into TiO2 lattice substitutionally. Catalytic activity systems of Pt/doped-TiO2 and Pt/undoped-TiO2 were fabricated to reveal the strong metal-support interaction effect during catalytic activity of CO oxidation reactions. By arc plasma deposition technique, platinum nanoparticles with mean size of 2.7 nm were deposited on the thin films of doped and undoped titanium dioxide. The CO oxidation was performed with 40 Torr CO and 100 Torr O2 with 620 Torr He carrier gas. Turn over frequency was observed two to three folds enhancement in case of Pt/doped TiO2 as compared to Pt/TiO2. The electronic excitation and the oxygen vacancies that were formed with the doping process were the plausible reasons for the enhancement of catalytic activity.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.163.2-163.2
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• 2010

We developed a simple method to synthesis a nitrogen doped graphene, nitrogen plasma treated graphene (NPG) sheets thought nitrogen plasma etching of graphene oxide (GO). X-ray photo electron spectroscopy (XPS) study of NPG sheets treated at various plasma conditions reveal that N-doping is classified to 3 kinds of binding configurations. The nitrogen doping concentration is at least 1.5 at % and up to 3 at% with changing of ratio of nitrogen configuration in NPG. Our group demonstrate ultracapacitor with high capacity and extremely durable using a NPG sheets that are comparable to pristine graphene supercapacitor, and pseudocapacitor using polymer and metal oxide with redox reaction, capacitance that are three-times higher, and a cycle life that are extremely stable. We also realized flexible capacitor by using the paper electrode that are coated by NPG sheets. NPG paper capacitor presented almost same performance compare with NPG on a metal substrate, and durability is much more enhanced than that. To additionally explain that how different kind of atoms in graphene layers can act as the ion absorption sites, we simulated the binding energy between nitrogen in graphene layer and ions in electrolyte. Increasing the energy density and long cycle life of ultracapacitor will enable them to compete with batteries and conventional capacitors in number of applications.

• 한국전기전자재료학회논문지
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• 제28권11호
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• pp.683-689
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• 2015

For the formation of $N^+$ doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a $SiO_2/Si$ is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert $N_2$ gas and dry oxidation.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.26-26
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• 2003

Lithium storage electrodes for rechargeable batteries require mixed electronic-ionic conduction at the particle scale in order to deliver desired energy density and power density characteristics at the device level. Recently, lithium transition metal phosphates of olivine and Nasicon structure type have become of great interest as storage cathodes for rechargeable lithium batteries due to their high energy density, low raw materials cost, environmental friendliness, and safety. However, the transport properties of this family of compounds, and especially the electronic conductivity, have not generally been adequate for practical applications. Recent work in the model olivine LiFePO$_4$, showed that control of cation stoichiometry and aliovalent doping results in electronic conductivity exceeding 10$^{-2}$ S/cm, in contrast to ~10$^{-9}$ S/cm for high purity undoped LiFePO$_4$. The increase in conductivity combined with particle size refinement upon doping allows current rates of >6 A/g to be utilized while retaining a majority of the ion storage capacity. These properties are of much practical interest for high power applications such as hybrid electric vehicles. The defect mechanism controlling electronic conductivity, and understanding of the microscopic mechanism of lithiation and delithiation obtained from combined electrochemical and microanalytical techniques, will be discussed

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.955-962
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• 2005

Power efficiency, lifetime and stable manufacturing processes are the crucial parameters for the success of organic light emitting diodes (OLEDs) in display and lighting applications. Highest power efficiencies of PIN-OLEDs for all principal colours and for bottom and top emission OLED structures have been demonstrated. The PIN structure, which means the incorporation of intentionally doped charge carrier transport layer in a suitable OLED layer setup, lowers the operating voltage to achieve highest power efficiencies. Up to now the n-doping of the electron transport layer has been done by alkali metal co-deposition. This has main draw-backs in terms of manufacturability, since the handling of large amounts of pure Cs is a basic issue in production lines. Here we present in detail results on PIN-OLEDs comprising a newly developed molecular n-dopant. All the previous OLED performance data based on PIN-OLEDs with alkali metal doping could be reproduced and will be further improved in the future. Hence, for the first time, a full manufacturing compatible PIN-OLED is available.

• 한국진공학회지
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• 제12권3호
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• pp.193-199
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• 2003

아크-마그네트론 복합 공정법에 의해 Cu, Ag 도핑된 TiN 나노 복합 화합물 박막을 합성하고 각 금속원소 종류 및 함량에 따른 기계적 특성 및 나노 구조로의 상변화 거동을 관찰하였다. 합성된 박막은 약 40 ㎬의 높은 경도치를 나타내었으며 2 at% 미만의 낮은 금속 원소 함량에서 최대 경도간을 나타내었다. 금속 원소 함량이 증가할수록 결정립 미세화 및 다결정화가 진행되어 초고경도 특성을 나타내는 나노구조 박막이 합성되었으며 도핑되는 금속원소 종류에 따라 나노 구조로의 상변화 기구가 상이함을 관찰하였다. TiN 박막내 도핑된 Cu는 Ti와 일부 결합을 이루면서 Ti의 자리를 치환하는 것으로 나타났으나, Ag는 Ti와 결합을 이루거나 Ti 격자 자리를 치환하는 것이 아니라 독립적으로 결정립계에 존재하여 charge transfer만을 발생시키는 것으로 관찰되었다.

• Transactions on Electrical and Electronic Materials
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• 제2권4호
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• pp.24-29
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• 2001

GaN films were grown for various Mg doping concentrations in metal-organic chemical vapor deposition. Below the Mg concentration of 10$^{19}$ ㎤, the thermally annealed sample shows the compensated phase to n-type GaN in Hall measurement. In the MB concentration of 4$\times$10$^{19}$ ㎤ corresponding to the hole carrier concentration of 2.6$\times$1$^{19}$ ㎤ there exists a photoluminescence center of the donor and the acceptor pair transition of the 3.28-eV band. This center is correlated with the defects for a shallow donor of the $V_{Ga}$ and for an acceptor of $Mg_{Ga}$ . The acceptor level shows the binding energy of 0.2-0.25 eV, which was observed by the photon energy of the photocurrent signal of 3.02-3.31 eV. Above the Mg concentration of 4$\times$10$^{19}$ ㎤, both the Mg doping level and Mg concentration were saturated and there Is a photoluminescence center of a deep donor and an acceptor pair transition of the 2.76-eV blue band.

• Korean Chemical Engineering Research
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• 제57권5호
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• pp.701-705
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• 2019

알칼라인 조건에서의 산소발생 반응(oxygen-evolution reaction: OER)은 다양한 에너지 시스템에 중요한 반응으로 여겨지고 있다. 큰 overpotential을 감소시키기 위해 다양한 촉매들이 개발되고 있으며, 그 중 NiO는 높은 활성도에 대한 가능성으로 인해 연구가 활발하게 진행되고 있다. 촉매의 표면에서 OER에 대한 메커니즘은 정확하게 규명되지는 않았지만, 산화물 촉매에서 Ni 또는 O vacancy와 같은 결함들은 많은 전기화학반응에서 활성점으로 여겨진다. 따라서, 본 연구에서는 nitrogen을 ethylenediamine을 이용하여 NiO의 O위치에 치환하여 Ni vacancy를 형성하고 그로 인해서 OER의 activity와 내구성에 어떠한 영향을 미치는지에 대해 분석해 보았다.