• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.5
• /
• pp.389-393
• /
• 2007

We fabricated field-effect transistor based carbon nanotubes(CNTs) directly grown by thermal chemical vapor deposition(CVD) and analyzed their performance. The Ethylene ($C_2H_4$), hydrogen($H_2$) and Argon(Ar) gases were used for the growth of CNTs at $700\;^{\circ}C$. The growth properties of CNTs on the device were analyzed by SEM and AFM. The electrical transport characteristics of CNT FET were investigated by I-V measurement. Transport through the nanotubes is dominated by holes at room temperature. By varying the gate voltage, we successfully modulated the conductance of FET device by more than 7 orders of magnitude.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1389-1399
• /
• 2015

This research suggests maximum power point tracking (MPPT) for the solar photovoltaic (PV) power scheme using a new constant voltage (CV) fractional order incremental conductance (FOINC) algorithm. The PV panel has low transformation efficiency and power output of PV panel depends on the change in weather conditions. Possible extracting power can be raised to a battery load utilizing a MPPT algorithm. Among all the MPPT strategies, the incremental conductance (INC) algorithm is mostly employed due to easy implementation, less fluctuations and faster tracking, which is not only has the merits of INC, fractional order can deliver a dynamic mathematical modelling to define non-linear physiognomies. CV-FOINC variation as dynamic variable is exploited to regulate the PV power toward the peak operating point. For a lesser scale photovoltaic conversion scheme, the suggested technique is validated by simulation with dissimilar operating conditions. Contributions are made in numerous aspects of the entire system, including new control algorithm design, system simulation, converter design, programming into simulation environment and experimental setup. The results confirm that the small tracking period and practicality in tracking of photovoltaic array.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.2
• /
• pp.354-358
• /
• 2013

This paper discusses the analysis of arc conductance in a gas circuit breaker (GCB) during current interruption process and the investigation method of the interruption capability. There are some limitations in the application of the computational fluid dynamics (CFD) for the implementation of an arc model around the current zero, despite the fact that it gives good results for the high-current phase arc. In this study, we improved the accuracy in the analysis of the interruption performance by attempting the method using CFD and a mathematical arc model. The arc conductance at 200 ns before current zero (G-200ns) is selected as the indicator to predict the current interruption of the Short Line Fault (SLF). Finally, the proposed method is verified by applying to the actual circuit breakers which have different interruption performances.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.4
• /
• pp.247-252
• /
• 2012

IGBT (insulated gate bipolar transistor) has been widely used around the power industry as it has good switching performance and its excellent conductance. In order to reduce power loss during switch turn-on state, it is essential to reduce its resistance. However, trade off relationship between breakdown voltage and device conductance is the greatest obstacle on the way of improvement. Floating island structure is one of the solutions. Still, under optimized device condition for the best performance, improvement rate is negligible. Therefore, this paper suggests adding trench gate on floating island structure to eliminate JFET (junction field effect transistor) area to reduce resistance and activate floating island effect. Experimental result by 2D simulation using TCAD, shows 20% improvement of turn-on state voltage drop.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.679-682
• /
• 2005

Negative-differential conductance (NDC) characteristics as well as negative-differential trans-conductance (NDT) characteristics have been observed in the room temperature I-V characteristics of Field-induced Inter-band Tunneling Effect Transistors (FITETs). These characteristics have been explained with inter-band tunneling physics, from which, inter-band tunneling current flows when the energy bands of degenerately doped regions align, and it does not flow when they don't. FITET is an SOI device and the body region is not directly connected to the external terminal. Therefore, Fermi energy in the body region is determined by electrical coupling among four regions - gate, source, drain and substrate. So, a quasi Fermi energy of the majority carriers in the floating body region can be changed by external voltages, and this causes the energy band movements in the body region, which determine whether the energy bands between degenerately doped junctions aligns or not. This is a key point for an explanation of NDT and NDC characteristics. In this paper, a quasi Fermi energy movement in the floating body region of FITET was investigated by a device simulation. This result was applied for the description of relation between quasi Fermi energy in the body region and external gate bias voltage.

• Proceedings of the SCSK Conference
• /
• 2003.09b
• /
• pp.456-457
• /
• 2003

The use of relaxing cosmetic products is more and more widespread on the self care market, since stress is considered as a major cause of discomfort in modem life. Cortisol, the stress hormone, helps the human body to regulate itself by acting on carbonhydrate, proteins and fat metabolisms. IgA are immune molecules involved in the stress response of the human body. The less the human body is stressed, the more the salivary IgA rate increases. Salivary cortisol and IgA have the advantage of being easily assessed with non invasive methods. Finally, conductance is the measurement of the modification in the electrical resistance of the skin. By this means, the measurement of the conductance enable the assessment of somebody's stress.(omitted)

• Journal of Korean Ophthalmic Optics Society
• /
• v.4 no.2
• /
• pp.105-111
• /
• 1999

This paper presents experimental results on the electrical properties of hydrogenated amorphous carbon films(a-C:H) prepared by PECVD. DC conductance of a-C:H was measured as a function of temperatures in the range of 100 to 423K. We studied two a-C:H films: one was well explained by the Mott's Variable Range Hopping(VRH) rule, but the other sample did not follow it. However, the conduction data of second sample were well fitted to Shimakawa's Multi-Phonon Hopping(MPH) model according to which conductivity is proportional to $T^M$ with m=15-17. but, in our samples, m was 10-12. Also a-C:H showed several bias effects like relaxation of conductance, bias-dependent conductance and the change of conductance slope in 1n(${\sigma}{\sqrt{T}}$) vs. $T^{1/4}$ plot. In this study we interpret these data by bias-dependent detrapping model.

• Applied Science and Convergence Technology
• /
• v.23 no.4
• /
• pp.192-199
• /
• 2014

The electronic property of graphene was investigated by hydrazine treatment. Hydrazine ($N_2H_4$) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utilized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.

• Transactions on Electrical and Electronic Materials
• /
• v.14 no.3
• /
• pp.148-151
• /
• 2013

The control of Ga doping in ZnO nanowires (NWs) by physical vapor deposition has been implemented and characterized. Various Ga-doped ZnO NWs were grown using the vapor-liquid-solid (VLS) method, with Au catalyst on c-plane sapphire substrate by hot-walled pulsed laser deposition (HW-PLD), one of the physical vapor deposition methods. The structural, optical and electrical properties of Ga-doped ZnO NWs have been systematically analyzed, by changing Ga concentration in ZnO NWs. We observed stacking faults and different crystalline directions caused by increasing Ga concentration in ZnO NWs, using SEM and HR-TEM. A $D^0X$ peak in the PL spectra of Ga doped ZnO NWs that is sharper than that of pure ZnO NWs has been clearly observed, which indicated the substitution of Ga for Zn. The electrical properties of controlled Ga-doped ZnO NWs have been measured, and show that the conductance of ZnO NWs increased up to 3 wt% Ga doping. However, the conductance of 5 wt% Ga doped ZnO NWs decreased, because the mean free path was decreased, according to the increase of carrier concentration. This control of the structural, optical and electrical properties of ZnO NWs by doping, could provide the possibility of the fabrication of various nanowire based electronic devices, such as nano-FETs, nano-inverters, nano-logic circuits and customized nano-sensors.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1193-1196
• /
• 2004

We have demonstrated the use of MWCNT as a nanoscale probe to monitor the activity of enzyme kinase. To immobilize the substrate peptide using carbodiimide chemistry, plasma or strong acid treatments were used to induce carboxyl groups on the sidewall of MWCNTs. After the susbtrate peptide immobilization, increase of conductance from MWCNT devices was observed. When peptide modified MWCNTs react with enzyme kinase, conductance decreases by several orders of magnitude, and this conductance change can be explained by the phosphorylation reaction of enzyme kinase. When the sample was incubated with phosphatase to dephosphorylate the substrate peptide, nearly complete recovery of the conductance signal has been observed. 4 for 6 devices appeared the same trends. So, we can confirm that we have monitored the kinase activity on the MWCNT surface by electrical detection.