• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.244.2-244.2
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• 2011

We introduce a novel and robust method for the preparation of nanocomposite multilayers, which allows the excellent photoluminescent (PL) properties as well as the accurate control over the composition and dimensions of multilayers. By exchanging the oleic acid stabilizers of CdSe@ZnS quantum dots (QDs) synthesized in organic solvent with 2-bromo-2-methylpropionic acid (BMPA) in the same solvent, these nanoparticles were be alternately deposited by nucleophilic substitution reaction with highly branched poly(amidoamine) dendrimer (PAMA) through layer-by-layer (LbL) assembly process. Our approach does not need to be transformed into the water-dispersible nanoparticles with electrostatic or hydrogen-bonding groups, which can deteriorate their inherent properties, for the built-up of multilayers. The nanocomposite multilayers including QDs exhibited the strong PL properties achieving densely packed surface coverage as well as long-term PL stability under atmospheric conditions in comparison with those of conventional LbL multilayers based on electrostatic interaction. Furthermore, we demonstrate that the flexible multilayer films with optical properties can be easily prepared using nucleophilic substitution reaction between bromo and amino groups in organic media. This robust and tailored method opens a new route for the design of functional film devices based on nanocomposite multilayers.

• Journal of IKEEE
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• v.23 no.3
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• pp.811-816
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• 2019

The silicon-adsorbed oxygen(Si-O) superlattice grown by ultra high vacuum-chemical vapor deposition(UHV-CVD) was introduced as an epitaxial barrier for silicon quantum electron devices. The current-voltage (I-V) measurement results show the stable and good insulating behavior with high breakdown voltage. It is apparent that the Si-O superlattice can serve as an epitaxially grown insulating layer as possible replacement of silicon-on-insulator(SOI). This thick barrier may be useful as an epitaxial insulating gate for field effect transistors(FETs). The rationale is that it should be possible to fabricate a FET on top of another FET, moving one step closer to the ultimate goal of future silicon-based three-dimensional integrated circuit(3DIC).

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.289.1-289.1
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• 2014

In this study, we made a organic thin film device in MIS(Metal-Insulator-Semiconductor) structure by using PVP (Poly vinyl phenol) as a insulating layer, and CdSe/ZnS nano particles which have a core/shell structure inside. We dissolved PVP and PMF in PGMEA, organic solvent, then formed a thin film through a spin coating. After that, it was cross-linked by annealing for 1 hour in a vacuum oven at $185^{\circ}C$. We operated FTIR measurement to check this, and discovered the amount of absorption reduced in the wave-length region near 3400 cm-1, so could observe decrease of -OH. Boonton7200 was used to measure a C-V relationship to confirm a properties of the nano particles, and as a result, the width of the memory window increased when device including nano particles. Additionally, we used HP4145B in order to make sure the electrical characteristics of the organic thin film device and analyzed a conduction mechanism of the device by measuring I-V relationship. When the voltage was low, FNT occurred chiefly, but as the voltage increased, Schottky Emission occurred mainly. We synthesized CdSe/ZnS and to confirm this, took a picture of Si substrate including nano particles with SEM. Spherical quantum dots were properly made. Due to this study, we realized there is high possibility of application of next generation memory device using organic thin film device and nano particles, and we expect more researches about this issue would be done.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.184-184
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• 2012

Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.