• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.904-907
• /
• 2003

We synthesized dendrimers containing light switchable units, azobenzene group. To apply to the molecular level devices or data storage system using Langmuir-Blodgett(LB) film, we firstly investigated the monolayer behavior using the surface pressure-area(${\pi}-A$) isotherms at air-water interface. And then the surface pressure shift of monolayer by light irradiation was also measured to the dendrimer with azobezene group. As a result, the monolayer of dendrimer with azobenzene group showed the reversible photo-switching behavior by the isomerization of azobenzene group in their periphery. This results suggest that the dendrimers with azobenzene group can be applied to high efficient nano-device of molecular level. And we measured the electrical properties by MIM and STM. The dendrimer with azobenzene group compared trans form and cis form at electrical properties.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.962-964
• /
• 1999

We studied emitting properties of devices fabricated using the spin-coating and Langmuir-Blodgett[LB] technique. The LB technique has the advantage of precise control of the thickness better than spin-coating method. Poly(3-hexylthiophene)[P3HT] LB films used as the emitting layer in light-emitting devices. LB monolayers were deposited 27 layers onto the indium-tin-oxide[ITO] as Y-type films by the vertical dipping method. The thickness is about 80nm. Absorption spectrum of LB films presented that P3HT is regiorandom conformation. Also, current-voltage-luminance characteristics and electroluminescence spectra of light-emitting devices fabricated by LB method is studied. In current-voltage-luminescence characteristics, turn-on voltage of P3HT LB film LEDs is higher than that of spin-coating LEDs. But electroluminescence spectrum is similar to the spin-coating LEDs. The orange-red light was clearly visible in a darkened room.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.2
• /
• pp.87-91
• /
• 2000

Metal ion complex of poly(N-(2,4-imidazoly)ethyl)maleimide-alt-l-octadecene (IMO-O) polymer used to confirm the possibility of molecular device made by Langmuir-Blodgett(LB) method. Electrical properties of the metal ion complex LB film were investigated using Metal/Insulator/Metal(MIM) structure. In the surface pressure-area($\pi$-A) isotherm of IMI-O polymer, the surface pressure at collapse point has a difference due to the interaction between polymer and metal ions. And the complex between polymer and metal ions could be verified through the investigation by Raman spectroscopy. In the current-voltage(I-V) property, the conductivity change of IMO-O polymer complexes due to the kinds of metal of metal ions couldn't be observed. However, the limiting area of molecules was changed by the concentration of the metal ions and the conductivity was increased with the occupied molecular area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.913-919
• /
• 2000

We give pressure stimulation into long chain fatty acid of LB thin films then manufacture a device under the accumulation condition that the state surface pressure is 20[mN/m]. In processing of a device manufacture, we can see the process is good from the change of a surface pressure for organic thin films and transfer ratio of area per molecule. The structure of manufactured device is Au/Arachidic acid/Al, the number of accumulated layers are 13, 17 and 19. The I-V characteristic of the device is measured from 0[V] to +1.5[V]. We have investigated the capacitance because this fatty acid system have a accumulated layers. The maximum value of measured current is increased as the number of accumulated layers are decreased. The capacitor properties of a thin film is better as the distance between electrodes is smaller. The results have shown the insulating materials and could control the conductivity by accumulated layers.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.1
• /
• pp.44-49
• /
• 2014

We were investigated by cyclic voltammetry to the stability through the electrochemical characteristics of phospholipid(L-${\alpha}$-phosphatidylethanolamine, LAPE) monolayer LB films. LAPE monolayer LB films was deposited by the LB method on the indium tin oxide(ITO) glass. The electrochemical properties was measured by cyclic voltammetry with a three-electrode system in 0.5 N, 1.0 N, 1.5 N and 2.0 N $KClO_4$ solution. The measuring range is continuously oxidized to 1650 mV, with an initial potential of -1350 mV was reduced. Scanning rates of 50, 100, 150, 200, and 250 mV/s was set. As a result, LB monolayer films of LAPE was appeared on irreversible processes by the oxidation current from the cyclic voltammogram. Diffusion coefficient (D) of LAPE was calculated 195, 15.9, 5.75, 1.38 and $0.754cm^2s^{-1}{\times}10^{-9}$ at 0.01 N, 0.05 N, 0.10 N, 0.15 N and 0.20 N $KClO_4$ solutions, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.307.2-307.2
• /
• 2016

In this study, we synthesized Au nanoparticles (AuNPs) in polyacrylonitrile (PAN) thin films using a simple annealing process in the solid phase. The synthetic conditions were systematically controlled and optimized by varying the concentration of the Au salt solution and the annealing temperature. X-ray photoelectron spectroscopy (XPS) confirmed their chemical state, and transmission electron microscopy (TEM) verified the successful synthesis, size, and density of AuNPs. Au nanoparticles were generated from the thermal decomposition of the Au salt and stabilized during the cyclization of the PAN matrix. For actual device applications, previous synthetic techniques have required the synthesis of AuNPs in a liquid phase and an additional process to form the thin film layer, such as spin-coating, dip-coating, Langmuir-Blodgett, or high vacuum deposition. In contrast, our one-step synthesis could produce gold nanoparticles from the Au salt contained in a solid matrix with an easy heat treatment. The PAN:AuNPs composite was used as the charge trap layer of an organic nano-floating gate memory (ONFGM). The memory devices exhibited a high on/off ratio (over $10^6$), large hysteresis windows (76.7 V), and a stable endurance performance (>3000 cycles), indicating that our stabilized PAN:AuNPs composite film is a potential charge trap medium for next generation organic nano-floating gate memory transistors.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1197-1199
• /
• 1993

The molecular electronic devices of organic materials are of current interest. Langmuir-Blodgett(LB) method is the most possible candidate for the development of the molecular electronic devices. One of the critical problems for applications of the LB films to the commercial products will be an electrical conductivity within a LB film. We studied the monolayer characteristics and electrical conductivity of the 1:1 mixture LB films of N-docosylquinolium-TCNQ and $TCNQ^0$. There were some differences in the $\pi-A$ isotherm and UV-visible absorption spectrum of N-docosylquinolium-TCNQ and 1:1 mixture. The small critical area of the $\pi-A$ isotherm for 1:1 mixture may result from the bilayer formation. We confirmed the incorporation of the $TCNQ^0$ with the N-docosylquinolium-TCNQ from the UV-visible absorption spectrum. But the electrical conductivity measured was $10^{-7}$ S/cm for the 1:1 mixture film layered at the surface pressure of 35 mN/m. We couldn't gain any electrical conductivity by mixing the $TCNQ^0$ into the N-docosylquinolium-TCNQ layer. We supposed that $TCNQ^0$ mixed in was not packed parallel to the TCNQ anion radical faces.

• Journal of the Korean Applied Science and Technology
• /
• v.32 no.3
• /
• pp.522-527
• /
• 2015

We applied a displacement current measurement technique for the study of L-${\alpha}$-dilauryl phosphatidylcholine (DLPC) monolayer. Displacement current was generated at the DLPC monolayer on the water surface, while induced by compression and expansion of the monolayer. Generation of Maxwell displacement current (MDC) was observed when surface areas per DLPC molecule were approximately $200{\AA}^2$ and $40{\AA}^2$. We investigated MDC for monolayer compression cycles, and found that MDC reached the maximum at the molecular area, which was measured right before surface pressure began to increase during compression cycles. The monolayer surface morphology of Langmuir-Blodgett (LB) films was characterized using atomic force microscope (AFM). As a result, we measured the result from the microscopic properties shown in the AFM images of LB films that molecules in the monolayer were in good orientations and the thickness of the monolayer ranged from 5 to 10 nm.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.636-636
• /
• 2013

Since first discovery of strong Raman spectrum of molecules adsorbed on rough noble metal, surface enhanced Raman scattering (SERS) has been widely used for detection of molecules with low concentration. Surface plasmons at noble metal can enhance Raman spectrum and using Au nanostructures as substrates of SERS has advantages due to it has chemical stability and biocompatibility. However, the photoluminescence (PL) background from Au remains a problem because of obtaining molecular vibration information. Recently, graphene, two-dimensional atomic layer of carbon atoms, is also well known as PL quenchers for electronic and vibrational excitation. In this study, we observed SERS of single layer graphene on or under monolayer of Au nanoparticles (NPs). Single layer graphene is grown by chemical vapor deposition and transferred onto or under the monolayer of Au NPs by using PMMA transfer method. Monolayer of Au NPs prepared using Langmuir-Blodgett method on or under graphene surface provides closed and well-packed monolayer of Au NPs. Scanning electron microscopy (SEM) and Raman spectroscopy (WItec, 532 nm) were performed in order to confirm effects of Au NPs on enhanced Raman spectrum. Highly enhanced Raman signal of graphene by Au NPs were observed due to many hot-spots at gap of closed well-packed Au NPs. The results showed that single layer graphene provides larger SERS effects compared to multilayer graphene and the enhancement of the G band was larger than that of 2D band. Moreover, we confirm the appearance of D band in this study that is not clear in normal Raman spectrum. In our study, D band appearance is ascribed to the SERS effect resulted from defects induced graphene on Au NPs. Monolayer film of Au NPs under the graphene provided more highly enhanced graphene Raman signal compared to that on the graphene. The Au NPs-graphene SERS substrate can be possibly applied to biochemical sensing applications requiring highly sensitive and selective assays.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.5
• /
• pp.201-205
• /
• 2003

We synthesized dendrimers containing light switchable units, azobenzene group. And the dendrimer containing 48 pyridinepropanol functional end group, which could form a complex structure with metal ions was synthesized. To apply to the molecular level devices or data storage system using Langmuir-Blodgett(LB) film, we firstly investigated the monolayer behavior using the surface pressure-area($\pi$-A) isotherms at air-water interface. And then the surface pressure shift of monolayer by light irradiation was also measured to the dendrimer with azobezene group. As a result, the monolayer of dendrimer with azobenzene group showed the reversible photo-switching behavior by the isomerization of azobenzene group in their periphery. The samples for electrical measurement were fabricated to two types which were pure dendrimer with pyridinepropanol group and its complexes with $Pt^4+$ ions by LB method. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage(I-V) characteristics of Metal/Dendrimer LB films/Metal(MIM) structure. And we have investigated different results in the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure dendrimer with pyridinevopanol group and its complex with $Pt^4+$ ions. In conclusion, it is demonstrated that the metal ion around dendrimer with pyri야nepropanol group can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties. This results suggest that the dendrimers with azobenzene group and pvridinedropanol group can be applied to high efficient nano-device of molecular level.