• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.343-343
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• 2011

ZnO has been introduced as one of the good candidates for next generation opto-electronics. Recently, ZnO is known to be suitable for the transparent electrode in organic solar cells and light emitting devices. The contact with n-type organic material has been studied due to the n-type properties of ZnO. However, the surface of ZnO has shown different electronic property with respect to its surface orientation. Therefore, it is presumed that there are differences in the interfacial electronic structures between organic materials and ZnO with different orientation. Therefore, it is required to classify the interfacial electronic structures according to the surface orientation of ZnO. In this study, we measured the interfacial electronic structures between the ZnO substrate having various orientations and a typical n-type organic material, tris-(8-hydroxyquinoline) aluminum (Alq3). In-situ x-ray and ultraviolet photoelectron spectroscopy measurements revealed the interfacial electronic structures. We found the changes in the electronic structures with respect to the orientation of ZnO substrate and it could be used to improve the contact between ZnO and Alq3.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.348-348
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• 2011

We present the interfacial electronic structures of electrodeposited Cu and Fe on bare and 1,4-phenylene diisocyanide (PDI)-functionalized Au nanoisland templates (NITs), and Au and Ag nanoparticles on transition metal oxide supports. Our discussion is based on the depth-profiling X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

• Vacuum Magazine
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• v.2 no.2
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• pp.4-11
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• 2015

During last two decades, remarkable progresses have been made in organic electronic devices, such as organic light-emitting device, organic photovoltaic and many other applied devices. Many of these progress are attributed to the multilayered/heterojunction device architectures, which could be achieved from the control of "interfacial energetics". In that sense, the interfacial electronic structures in organic electronic devices have a decisive role in device performance. However, the prediction of the interfacial electronic structures from each separate material is not trivial. Many complex phenomena occur at the interface and these can be only understood from thorough measurements on interfacial electronic structures in situ. Photoemission and inverse photoemission spectroscopy have been known as the most proper measurement tools to analyze these interfacial electronic structures. In this review, the basic principles of (inverse) photoemission spectroscopy and typical measurement results on organic/inorganic interfaces are introduced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.223-227
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• 2004

We have studied the interfacial diffusion of Fe/Cr multilayers using synchrotron x-ray techniques, such as x-ray reflectivity, extended x-ray absorption fine structures (EXAFS), and high-resolution x-ray scattering. The results of x-ray reflectivity indicated that the interfacial roughness of Fe/Cr multilayers increased with the Cr-layer thickness. The Fourier transform (FT) of EXAFS data clearly showed that the Fe atoms dominantly diffused into the stable Cr layers at the Fe/Cr interface. The results of high-resolution x-ray scattering supported the interfacial diffusion of Fe atoms. Out study revealed that the dominantly interfacial diffusion of Fe atoms into the Cr layers effects the interfacial roughness of the Fe/Cr multilayers.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.277-277
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• 2012

PCDTBT (Poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]) is an attractive material as a semiconducting polymer for organic thin film transistor (OTFT) and organic solar cell (OSC). High power conversion efficiency (~6%) under simulated AM 1.5G solar illumination of bulk-heterojunction solar cell with PCDTBT and [6,6]-phenyl C60 butyric acid methyl ester (PC61BM) blend was reported. In OSC, it is known that the band alignment at the interface between donor and acceptor is critical. Therefore, we studied the interfacial electronic structures of PCDTBT and PC61BM. The polymers are deposited by electro-spray on gold and In-situ x-ray and ultraviolet photoelectron spectroscopy measurements revealed the interfacial electronic structures. We obtained the energy level alignment between two materials and the different interface formation was observed with different deposition order.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.84-87
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• 2003

The interfacial diffusion in Fe/Cr/MgO(001) multilayers has been studied using synchrotron x-ray techniques, such as x-ray reflectivity, extended x-ray absorption fine structures (EXAFS), and anomalous x-ray scattering (AXS). The results of x-ray reflectivity indicated that the interfacial roughness of Fe/Cr multilayers with Cr-$4{\AA}$-thick was larger than that with Cr-$4{\AA}$-thick. The results of EXAFS indicated that the Fe element dominantly diffuse into the stable Cr layers at the Fe/Cr interface. The AXS was certified the existence of the interdiffused Fe element in the Cr layers. Our study revealed that the rough interface of the Fe/Cr multilayers was caused by the interfacia diffusion of Fe element into the Cr layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.61.2-61.2
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• 2015

In the past decades, green energy, such as solar energy, wind power, hydropower, biomass energy, geothermal energy, and so on, has been widely investigated and developed to solve energy shortage. Recently, organic solar cells have attracted much attention, because they have many advantages, including low-cost, flexibility, light weight, and easy fabrication [1-3]. Organic solar cells are as a potential candidate of the next generation solar cells. In this abstract, to improve the power conversion efficiency and the stability, the inverted polymer solar cells with various structures were developed [4-6]. The novel cell structures included the P3HT:PCBM inverted polymer solar cells with AZO nanorods array, with pentacene-doped active layer, and with extra P3HT interfacial layer and PCBM interfacial layer. These three difference structures could respectively improve the performance of the P3HT:PCBM inverted polymer solar cells. For the inverted polymer solar cells with AZO nanorods array as the electronic transportation layer, by using the nanorod structure, the improvement of carrier collection and carrier extraction capabilities could be expected due to an increase in contact area between the nanorod array and the active layer. For the inverted polymer solar cells with pentacene-doped active layer, the hole-electron mobility in the active layer could be balanced by doping pentacene contents. The active layer with the balanced hole-electron mobility could reduce the carrier recombination in the active layers to enhance the photocurrent of the resulting inverted polymer solar cells. For the inverted polymer solar cells with extra P3HT and PCBM interfacial layers, the extra PCBM and P3HT interfacial layers could respectively improve the electron transport and hole transport. The extra PCBM interfacial layer served another function was that led more P3HT moving to the top side of the absorption layer, which reduced the non-continuous pathways of P3HT. It indicated that the recombination centers could be further reduced in the absorption layer. The extra P3HT interfacial layer could let the hole be more easily transported to the MoO3 hole transport layer. The high performance of the novel P3HT:PCBM inverted polymer solar cells with various structures were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.47-51
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• 2000

A modified direct bonding technique employing a wet chemical deposition of $SiO_2$ film on a wafer surface to be bonded is proposed for the fabrication of Si-$SiO_2$-Si structures. Structural and electrical quality of the bonded wafers is studied. Satisfied insulating properties of interfacial $SiO_2$ layers are demonstrated. Elastic strain caused by surface morphology is investigated. The diminution of strain in the grooved structures is semi-quantitatively interpreted by a model considering the virtual defects distributed over the interfacial region.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.67-67
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• 2011

Compound semiconductor/CNTs composites have shown considerably improved efficiency improvement in photovoltaic devices, which is often attributed to two different factors. One is the formation of efficient electronic energy cascade structures. The other effect of CNTs on the performance of photovoltaic devices is the decrement of interfacial resistance. The interfacial resistances at n-type/ p-type materials and/or n-type materials/TCO electrode are reduced by an outstanding electrical property of CNTs. In addition to the effects of CNTs, we report the third reason for increment of efficiency in photovoltaic devices by CNT's well-known electrical field enhancement effects. The improved ${\beta}$ values in reverse-FE currents of CIGS electrode with SWNTs layers indicate the enhancement of electrical field in photovoltaic devices, which implies the acceleration of the electron transfer rate in the cell. Due to the formation of an efficient electronic energy cascade structure and the decrease of the interfacial resistance as well as the improvement of the electrical field in the photovoltaic devices, the power conversion efficiency of electrochemically deposited superstrate-type CIGS solar cells was increased 24.3% in the presence of SWNTs and showed 10.40% conversion efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.310-313
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• 2002

Structures obtained with a direct boning of two FZ silicon wafers joined in such a way that a smooth surface of one wafer was attached to the grooved surface of the other were studied. A square net of grooves was made with a conventional photo lithography process. After high temperature annealing the appearance of voids and the rearrangement of structural defects were observed with X-ray diffraction topography techniques. It was shown that the formation of void free grooved boundaries was feasible. In the cases when particulate contamination was prevented, the voids appeared in the grooved structures could be eliminated with annealing. Since it was found that the flattening was accompanied with plastic deformation, this deformation was suggested to be intensively involved in the process of void removal. A model was proposed explaining the interaction between the structural defects resulted in "a dissolution" of cavities. The described processes may occur in grooved as well as in smooth structures, but there are the former that allow to manage air traps and undesirable excess of dislocation density. Grooves can be paths for air leave. According to the established mechanisms, if not outdone, the dislocations form local defect arrangements at the grooves permitting the substantial reduction in defect density over the remainder of the interfacial area.