• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.80-83
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• 2000

In this work we deposited Pentacene thin film by OMBD at the various substrate temperatures, deposition rate and the various annealing temperatures for the fabrication of organic TFT and investigated the electrical and film surface characteristics such as sheet resistance, contact resistance and conductance Film thickness were measured by $\alpha$-step and the sheet resistance, contact resistance and conductance were extracted from the relation between the distance of the contacts and the resistance. During the film deposition the substrate temperature was held at 3$0^{\circ}C$, 4$0^{\circ}C$, 5$0^{\circ}C$, 6$0^{\circ}C$, 8$0^{\circ}C$ and 10$0^{\circ}C$, respectively. After the film deposition, Au contact was deposited by thermal evaporation. For the effect of annealing, the thin film was annealed in the nitrogen environment at 10$0^{\circ}C$ and 14$0^{\circ}C$ for 10 seconds, respectively. Film surface characteristics at the vatious substrate temperatures were measured by AFM. The crystallization of thin film was improved as the substrate temperatures were increased and the maximum gram size was 4${\mu}{\textrm}{m}$. The conductivity of thin film was found to be 7.40 $\times$10$^{-7}$ ~ 7.78$\times$10$^{-6}$ S/cm and the minimum contact resistance was 2.5324 ㏁.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.862-866
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• 2012

Surface passivation of AlGaN/GaN heterojunction structure was examined through the thermal oxidation of evaporated Al. The Al-oxide passivation increased channel conductance of two dimensional electron gas (2DEG) on the AlGaN/GaN interface. The sheet resistance of 463 ohm/${\Box}$ for 2DEG channel before $Al_2O_3$ passivation was decreased to 417 ohm/${\Box}$ after passivation. The oxidation of Al induces tensile stress to the AlGaN/GaN structure and the stress seemed to enhance the sheet carrier density of the 2DEG channel. In addition, the $Al_2O_3$ films formed by thermal oxidation of Al suppressed thermal deterioration by the high temperature annealing.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.228.2-228.2
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• 2014

Characteristics of high Fermi velocity, high mechanical strength, and transparency offer tremendous advantages for using graphene as a promising transparent conducting material [1] in electronic devices. Although graphene is a prospective candidate for touch sensor with strong mechanical properties [2] and flexibility, only few investigations have been carried out in the field of sensor as a device form. In this study, we suggest ultra-highly sensitive and transparent graphene touch sensor fabricated by single layer graphenes. One of the graphene layers is formed in the top panel as a disconnected graphene beam transferred on PDMS, and the other of the graphene layer is formed with line-patterning on the bottom panel of triple structure PET/PI/SiO2. The touch sensor shows characteristics of flexible. Its transmittance is approximately 75% where transmittance of the top panel and the bottom panel are 86.3% and 87%, respectively, at 550 nm wavelength. Sheet resistance of each graphene layer is estimated as low as $971{\Omega}/sq$. The results show that the conductance change rate (${\Delta}C/C0$) is $8{\times}105$ which depicts ultra-high sensitivity. Moreover, reliability characteristic confirms consistent behavior up to a 100-cycle test.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.490-490
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• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Journal of Hydrogen and New Energy
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• v.27 no.3
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• pp.276-282
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• 2016

The effects of conductive additives in a $La_{0.8}Sr_{0.2}MnO_3$ perovskite bifunctional electrode for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated in an alkaline solution. Highly porous carbon black (CB) and Ni powder were added to the bifunctional electrodes as conductive additives. The surface morphologies of electrodes containing CB and Ni were observed by scanning electron microscopy (SEM). The current densities for both ORR and OER were changed by the addition of CB. The conductive additive changed physical properties of bifunctional electrodes such as the sheet conductance, gas permeability and contact angle. It was observed that the air permeability of electrode was most effective to enhance the currents for ORR and OER.