• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.221-221
• /
• 2013

Striving to replace the well known silicon nanocrystals embedded in oxides with solution-processable charge-trapping materials has been debated because of large scale and cost effective demands. Herein, a silicon quantum dot-polystyrene nanocomposite (SiQD-PS NC) was synthesized by postfunctionalization of hydrogen-terminated silicon quantum dots (H-SiQDs) with styrene using a thermally induced surface-initiated polymerization approach. The NC contains two miscible components: PS and SiQD@PS, which respectively are polystyrene and polystyrene chains-capped SiQDs. Spin-coated films of the nanocomposite on various substrate were thermally annealed at different temperatures and subsequently used to construct metal-insulator-semiconductor (MIS) devices and thin film field effect transistors (TFTs) having a structure p-$S^{++}$/$SiO_2$/NC/pentacene/Au source-drain. C-V curves obtained from the MIS devices exhibit a well-defined counterclockwise hysteresis with negative fat band shifts, which was stable over a wide range of curing temperature ($50{\sim}250^{\circ}C$. The positive charge trapping capability of the NC originates from the spherical potential well structure of the SiQD@PS component while the strong chemical bonding between SiQDs and polystyrene chains accounts for the thermal stability of the charge trapping property. The transfer curve of the transistor was controllably shifted to the negative direction by chaining applied gate voltage. Thereby, this newly synthesized and solution processable SiQD-PS nanocomposite is applicable as charge trapping materials for TFT based memory devices.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.8
• /
• pp.1747-1752
• /
• 2012

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane (BTMSM) and oxygen mixed precursor by the chemical vapor deposition. The dielectric constant is measured by MIS(metal/insulator/Si) structure, but it could decrease the reliability because the uniformity is not assured. To research the dielectric constant of SiOC film, the range of low polarization was researched in SiOC film using the optical analysis and hardness, and then calculated the dielectric constant of SiOC film with amorphous structure of high degree. After annealing, the dielectric constant of SiOC film was decreased owing to the lowering of polarization, and FTIR spectra of the main bond was shifted to higher wave number. The main bond of 950~1200 cm-1 was composed of the Si-C and Si-O bonds. The intensity increases in Si-O bond infers the bonding strength became stronger than that of deposited film. Annealed SiOC film showed 2.06 in dielectric constant.

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

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.1
• /
• pp.50-55
• /
• 2020

Porcelain insulators have been used for a long time in 154 kV power transmission lines. They are likely to be exposed to sudden failure because of product deterioration. This study was conducted to evaluate the quality of porcelain insulators. After stresses were applied, the damaged regions of aged insulators were investigated in terms of chemical composition, material structure, and other properties. For porcelain insulators that were in service for a long time, the mechanical failure load was 126 kN, whereas the average mechanical failure load was 167.3 kN for new products. It was also determined that corrosion occurred at the metal pin part due to the penetration of moisture into the gap between the pin and the ceramic. Statistical analyses of failure were performed to identify the portion of the insulators that were broken. Cristobalite porcelain insulators fabricated without alumina additives had a high failure rate of 54% for the porcelain component. In the case of the addition of Alumina (Al₂O₃) to the porcelain insulators to improve the strength of the ceramic component, a more frequent damage rate of the cap and pin of 73.3% and 27%, respectively, was observed. This study reports on the material component of SiO₂ and the percentage of alumina added, with respect to the mechanical properties of porcelain insulators.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.242-242
• /
• 2016

Magnetite, Fe3O4, is a ferrimagnet with a cubic inverse spinel structure and exhibits a metal-insulator, Verwey, transition at about 120 K.[1] It is predicted to possess as half-metallic nature, 100% spin polarization, and high Curie temperature (850 K). Cobalt ferrite is one of the most important members of the ferrite family, which is characterized by its high coercivity, moderate magnetization and very high magnetocrystalline anisotropy. It has been reported that the CoFe2O4/Fe3O4 bilayers represent an unusual exchange-coupled system whose properties are due to the nature of the oxide-oxide super-exchange interactions at the interface [2]. In order to evaluate the effect of interface interactions on magnetic and transport properties of ferrite and cobalt ferrite, the CoFe2O4/Fe3O4 superlattices on MgO (100) substrate have been fabricated by molecular beam epitaxy (MBE) with the wave lengths of 50, and $200{\AA}$, called $25{\AA}/25{\AA}$ and $100{\AA}/100{\AA}$, respectively. Streaky RHEED patterns in sample $25{\AA}/25{\AA}$ indicate a very smooth surface and interface between layers. HR-TEM image show the good crystalline of sample $25{\AA}/25{\AA}$. Interestingly, magnetization curves showed a strong antiferromagnetic order, which was formed at the interfaces.

• Journal of the Korean Vacuum Society
• /
• v.18 no.6
• /
• pp.435-439
• /
• 2009

The reason of lowering the dielectric constant of SiOC film was studied using parameters obtained from C-V measurement and refractive index. SiOC film was formed by the force of ionic bonding during the recombination of dissociated gases. Generally, the dielectric constant was obtained from the square of the refractive index or C-V measurement using the metal/insulator/Si structure. The dielectric constant consists of the ionic and electronic elements. It was researched about the dielectric constant of SiOC film using the average of the ionic and electronic elements. The dielectric constant decreased after annealing process. As deposited films trended toward the dielectric constant consisted of most ionic elements, on the other hand, annealed films mostly consisted of electronic elements. Because the effect of ionic elements reduced after annealing. Consequently, it was found that the electronic effect of SiOC film increased and the ionic effect of SiOC film decreased by the after-annealing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.172-173
• /
• 2006

Metal-ferroelectric-insulator-semiconductor (MFIS) structures with $Bi_{3.35}La_{0.75}Ti_3O_{12}$ (BLT) ferroelectric film and Zirconium oxide ($ZrO_2$) layer were fabricated on p-type Si(100). $ZrO_2$ and BLT films were prepared by sol-gel technique. Surface morphologies of $ZrO_2$ and BLT film were measured by atomic force microscope (AFM). The electrical characteristics of Au/$ZrO_2$/Si and Au/BLT/$ZrO_2$/Si film were investigated by C-V and I-V measurements. No hysteretic characteristics was observed in the C-V curve of the Au/$ZrO_2$/Si structure. The memory window width m C-V curve of the Au/BLT/$ZrO_2$/Si diode was about 1.3 V for a voltage sweep of ${\pm}5$ V. The leakage current of Au/$ZrO_2$/Si and Au/BLT/$ZrO_2$/Si structures were about $3{\times}10^{-8}$ A at 30 MV/cm and $3{\times}10^{-8}$ A at 3 MV/cm, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.4
• /
• pp.350-354
• /
• 2009

$Al_{2}O_{3}$ thin films were deposited on GaN(0001) by using a Remote Plasma Atomic Layer Deposition(RPALD) technique with a trimethylaluminum(TMA) precursor and oxygen radicals in the temperature range of $25{\sim}500^{\circ}C$. The growth rate per cycle was varied with the substrate temperature from $1.8{\AA}$/cycle at $25^{\circ}C$ to $0.8{\AA}$/cycle at $500^{\circ}C$. The chemical structure of the $Al_{2}O_{3}$ thin films was studied using X-ray photoelectron spectroscopy(XPS). The electrical properties of $Al_{2}O_{3}$/GaN Metal-Insulator-Semiconductor (MIS) capacitor grown at a $300^{\circ}C$ process temperature were excellent, a low electrical leakage current density(${\sim}10^{-10}A/cm^2$ at 1 MV) at room temperature and a high dielectric constant of about 7.2 with a thinner oxide thickness of 12 nm. The interface trap density($D_{it}$) was estimated using a high-frequency C-V method measured at $300^{\circ}C$. These results show that the RPALD technique is an excellent choice for depositing high-quality $Al_{2}O_{3}$ as a Sate dielectric in GaN-based devices.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.7
• /
• pp.1-8
• /
• 2008

We fabricated flexible electrophoretic display(EPD) driven by organic thin film transistors(OTFTs) on plastic substrate. We designed the W/L of OTFT to be 15, considering EPD's transient characteristics. The OTFTs employed bottom contact structure and used Al for gate electrode, the cross-linked polyvinylphenol for gate insulator, pentacene for active layer. The plastic substrate was coated by PVP barrier layer in order to remove the islands which were formed after pre-shrinkage process and caused the electrical short between bottom scan and top data metal lines. Pentacene active layer was confined within the gate electrodes so that the off current was controlled and reduced by gate electrodes. Especially, PVA/Acryl double layers were inserted between EPD panel and OTFT-backplane in order to protect OTFT-backplane from the damages created by lamination process of EPD panel on the backplane and also accommodate pixel electrodes through via holes. From the OTFT-backplane the mobility was $0.21cm^2/V.s$, Ion/Ioff current ratio $10^5$. The OTFT-EPD panel worked successfully and demonstrated to display some patterns.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.21 no.4
• /
• pp.52-57
• /
• 1984

The electrical properties and their instability of InP tunnel MIS diodes fabricated by inserting the chemically grown oxide between metal and n-lnP (100) surface have been in-vestigated. The structure of the gown oxide was the mixture of In2O3 and P2O5, as was other low-temperature grown oxide, and its thickness was estimated to be the order of 200 $A^{\circ}$. The forward and reverse currents increased even with slight heat treatment of diodes in vacuum, and they were reduced when the diodes were exposed to humid ambient. It was discussed that the observed instability in I-V characteristics is due to a change of the physicochemical properties of the oxide film and of the interface states between oxide and InP according to the absorption of H2O.