• Journal of Magnetics
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• v.15 no.1
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• pp.17-20
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• 2010

The relationship between ferromagnet anisotropic magnetization and the antiferromagnet atomic spin configuration was investigated for various angles of the uniaxial deposition magnetic field of the FeMn layer in the Corning glass/Ta(5nm)/NiFe(7nm)/FeMn(25nm)/Ta(5nm) multilayer that was prepared by the ion beam sputter deposition. The exchange bias field ($H_{ex}$) obtained from the measurement of the easy-axis MR loop decreased to 40 Oe at the deposition field angle of $45^{\circ}$, and to 0 Oe at the angle of $90^{\circ}$. When the difference between the uniaxial axis between the ferromagnet NiFe and the antiferromagnet FeMn was $90^{\circ}$, the strong antiferromagnetic dipole moment of FeMn caused the weak ferromagnetic dipole moment of NiFe to rotate in the interface.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.569-574
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• 2014

Inverted bulk hetero-junction polymer solar cells (iPSC) composed of P3HT/PC61BM blends on the ZnO modified with benzoic acid derivatives-based self-assembled monolayers (SAM) are fabricated. Compared with the device using the pristine ZnO, the devices with ZnO surface modified SAMs derived from benzoic acid such as 4-(diphenylamino)benzoic acid (DPA-BA) and 4-(9H-carbazol-9-yl)benzoic acid (Cz-BA) as an electron transporting layer show improved the performances. It is mainly attributed to the favorable interface dipole at the interface between ZnO and the active layer, the eective passivation of the ZnO surface traps, decrease of the work function and facilitating transport of electron from PCBM to ITO electrode. The power conversion eciency (PCE) of iPSCs based on DPA-BA and Cz-BA treated ZnO reaches 2.78 and 2.88%, respectively, while the PCE of the device based on untreated ZnO is 2.49%. The open circuit voltage values ($V_{oc}$) of the devices with bare ZnO and SAM treated ZnO are not much different. Whereas, higher the fill factor (FF) and lower the series resistance ($R_s$) are obtained in the devices with SAMs modification.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1059-1060
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• 2009

We have investigated the pristine alkali metal doping effect which is the Fermi level of alkali metal doped Alq3 shifts toward the LUMO. In-situ measurements of synchrotron radiation photoelectron spectroscopy revealed that the interface dipole or bend bending in previous reports are not the pristine alkali metal doping effect

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.112-114
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• 2009

Charge injection at electrode-organic interfaces is key to the performance, lifetime and stability of organic electronic devices. The link between fundamental material properties and the energy-level alignment at electrode-organic interfaces will be discussed. In addition the impact of the injection barrier height-a parameterization of the energylevel alignment-on device characteristics will also be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.8-10
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• 2010

We report the enhancement of hole injection using thermally evaporated $CuO_x$ layer between Ag anode and 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl ($\alpha$-NPD) in top-emitting organic light-emitting diode (TEOLED). The operation voltage at the current density of $1mA/cm^2$ of TEOLEDs decreased from 6.2 V to 5.0 V as the $CuO_x$ layer inserted between Ag and $\alpha$-NPD. $\alpha$-NPD was deposited in situ on Ag/$CuO_x$ and Ag anodes, and their interface dipole energies were quantitatively determined using synchrotron radiation photoemission spectroscopy. The dipole energy of Ag/$CuO_x$ was lower by 0.05 eV even though Ag/$CuO_x$ had a higher work function. The work function of Ag/$CuO_x$ is higher by 0.53 eV than that of Ag, resulting in a decrease of the turn-on voltage via reduction of hole injection barrier.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.69-75
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• 1999

The characteristics of $H_2$ gas detection have been investigated using the Pt-MIS capacitor composed of the LPCVD nitride on the oxide. The flat band voltage shift is measured as 0.1 V in 1,000 ppm $H_2$ gas ambient and to be independent of Pt catalyst thickness. It is found that the flatband voltage shift is proportional to the hydrogen concentrations. The response and recovery time of Pt-MIS capacitor are 5 mins and 25 mins respectively. The samples of 30nm thick Pt revealed much higher sensitivity than that of 150nm samples. The samples of 150nm Pt showed that the flatband voltage shift of the device is due to the formation of the dipole layer of the adsorbed hydrogen atoms at the Pt-insulator interface.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.382.1-382.1
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• 2014

Graphene field-effect transistors (GFET) is one of candidates for future high speed electronic devices since graphene has unique electronic properties such as high Fermi velocity (vf=10^6 m/s) and carrier mobility ($15,000cm^2/V{\cdot}s$) [1]. Although the contact property between graphene and metals is a crucial element to design high performance electronic devices, it has not been clearly identified. Therefore, we need to understand characteristics of graphene/metal contact in the GFET. Recently, it is theoretically known that graphene on metal can be doped by presence of interface dipole layer induced by charge transfer [2]. It notes that doping type of graphene under metal is determined by difference of work function between graphene and metal. In this study, we present the GFET fabricated by contact metals having high work function (Pt, Ni) for p-doping and low work function (Ta, Cr) for n-doping. The results show that asymmetric conductance depends on work function of metal because the interfacial dipole is locally formed between metal electrodes and graphene. It induces p-n-p or n-p-n junction in the channel of the GFET when gate bias is applied. In addition, we confirm that charge transfer regions are differently affected by gate electric field along gate length.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1343-1346
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• 2005

Self assembled monolayers (SAM) are generally used at the anode/organic interface to enhance the carrier injection in organic light emitting devices, which improves the electroluminescence performance of organic devices. This paper reports the use of SAM of 1-decanethiol (H-S(CH2)9CH3) at the cathode/organic interface to enhance the electron injection process for organic light emitting devices. Aluminum (Al), tris-(8-hydroxyquionoline) aluminum (Alq3), N,N'-diphenyl-N,N'-bis(3 -methylphenyl)-1,1'- diphenyl-4,4'-diamine (TPD) and indium-tin-oxide (ITO) were used as bottom cathode, an emitting layer (EML), a hole-transporting layer (HTL) and a top anode, respectively. The results of the capacitancevoltage (C-V), current density -voltage (J-V) and brightness-voltage (B-V), luminance and quantum efficiency measurements show a considerable improvement of the device performance. The dipole moment associated with the SAM layer decreases the electron schottky barrier between the Al and the organic interface, which enhances the electron injection into the organic layer from Al cathode and a considerable improvement of the device performance is observed. The turn-on voltage of the fabricated device with SAM layer was reduced by 6V, the brightness of the device was increased by 5 times and the external quantum efficiency is increased by 0.051%.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.1014-1018
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• 2007

We have demonstrated the enhancement of the power efficiency and device lifetime of organic light-emitting diodes (OLEDs) by introducing the ETL 1 / ETL2 (composite ETL) structure between EML and cathode and the HIL1 (composite HIL) / HIL2 between anode and HTL. Compared to reference devices retaining conventional architecture, novel OLED structure shows an outstanding EL efficiency that is 1.6 times higher (${\sim}4.5$ lm/w versus ${\sim}$ 2.71 lm/w for the reference device) and lower driving voltage $({\bigtriangleup}V>1V)$, but also a longer lifetime and smaller operating voltage drift over time. It is suggested in this work that the device performance can be improved by in-situ ohmic contact through novel electron controlled structure and reduction of charge accumulation in the interface through composite HIL

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2293-2298
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• 2011

In this paper, A tag antenna structure for RFID application with resonant frequency of 920MHz is proposed using the meander line technique and Evolution Strategy. Miniaturization structure design for a tag antenna is performed by structure combining the half-wave dipole with a meander line. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is made for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The optimized tag antenna size is 63mm ${\times}$ 15mm ${\times}$ 1mm. And the proposed antenna is realized on FR-4 substrate (${\epsilon}_r=4.4$, $tna{\delta}=0.02$).