• Journal of the Korean Ceramic Society
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• v.38 no.5
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• pp.492-498
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• 2001

Ba$_{0.5}$Sr$_{0.5}$TiO$_3$타겟을 이용 Pt/Ti/SiO/Si 기판 위에 R.F magnetron sputtering 방법으로 BST 박막을 증착하여 다양한 열처리 조건에 따른 BST 박막의 전기적 성질(정전용량, 누설전류)에 대해 박막의 결정성과 미세구조의 연관성에 대하여 연구하였다. BST 박막의 유전상수는 grain size에 영향 받으며, 열처리 온도가 증가할수록 유전상수는 증가함을 보였고 온도에 따른 누설전류는 저전압 영역에서는 Hopping conduction, 고전압 영역에서는 Schottky conduction mechanism을 따르는 것으로 나타났다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.270-274
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• 1997

The numerical model that can describe the ignition of the pseudospark discharge using hybrid fluid-particle method has been developed. The evolution process of the discharge has been divided into four phases along the potential distribution. After the plasma enters in the hollow cathode, the confining effect which is one of hollow cathode properties occurs and the electron current on anode rises rapidly. As the plasma expands successively, the sheath contracts and as the electric field in the sheath increases, the field-enhanced thermionic emission(Schottky emission) occurs. From numerical results, the physical mechanism that causes the rapid current rise in the ignition of the pseudospark discharge could be identified.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.231-235
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• 2019

We investigated the facile and effective strategy for sensitive and selective $C_2H_5OH$ sensors based on the In-decorated NiO nanoigloos. The In-decorated NiO nanoigloos is fabricated by RF sputtering using 750 nm-diameter polystyrene beads using a soft-template. The morphological evolution based on the Van der Drift model was generated through a heterojunction between In metal and NiO, resulting in a pyramidal rough surface. Upon decorating the In on the NiO surface, high sensitivity and selectivity to $C_2H_5OH$ were observed, and gas sensing mechanism was demonstrated by a high surface-to-volume and double Schottky barrier. We are confident that the method presented in this study will have a significant impact on the fabrication of effective nanostructures and their application for the gas sensors.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.239-244
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• 2017

We experimentally investigate the physical mechanism for asymmetrical degradation in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) under simultaneous gate and drain bias stresses. The transfer curves exhibit an asymmetrical negative shift after the application of gate-to-source ($V_{GS}$) and drain-to-source ($V_{DS}$) bias stresses of ($V_{GS}=24V$, $V_{DS}=15.9V$) and ($V_{GS}=22V$, $V_{DS}=20V$), but the asymmetrical degradation is more significant after the bias stress ($V_{GS}$, $V_{DS}$) of (22 V, 20 V) nevertheless the vertical electric field at the source is higher under the bias stress ($V_{GS}$, $V_{DS}$) of (24 V, 15.9 V) than (22 V, 20 V). By using the modified external load resistance method, we extract the source contact resistance ($R_S$) and the voltage drop at $R_S$ ($V_{S,\;drop}$) in the fabricated a-IGZO TFT under both bias stresses. A significantly higher RS and $V_{S,\;drop}$ are extracted under the bias stress ($V_{GS}$, $V_{DS}$) of (22 V, 20V) than (24 V, 15.9 V), which implies that the high horizontal electric field across the source contact due to the large voltage drop at the reverse biased Schottky junction is the dominant physical mechanism causing the asymmetrical degradation of a-IGZO TFTs under simultaneous gate and drain bias stresses.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.159-163
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• 2003

ln this work, we studied electrical characteristics and leakage current mechanism of $Ta_2O_{5}$ MOS(Metal-Oxide-Semiconductor) devices. $Ta_2O_{5}$ thin film (63 nm) was deposited by ALD(Atomic Layer Deposition) method at temperature of 235 $^{\circ}C$. The structures of the $Ta_2O_{5}$ thin films were examined by XRD(X-Ray Diffraction). From XRD, it is found that the structure of $Ta_2O_{5}$ is single phase and orthorhombic. From capacitance-voltage (C-V) anaysis, the dielectric constant was 19.4. The temperature dependence of current density-electric field (J-E) characteristics of $Ta_2O_{5}$ thin film was studied at temperature range of 300 - 423 K. In ohmic region (<0.5 MV/cm), the resistivity was 2.456${\times}10^{14}$ ($\omega{\cdot}cm$ at 348 K. The Schottky emission is dominant at lower temperature range from 300 to 323 K and Poole-Frenkel emission is dominant at higher temperature range from 348 to 423 K.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.60-65
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• 1998

Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett(LB) films have been investigated through a study of surface pressure-area $\pi$-A isotherms, AFM (atomic force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the $\pi$-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m-1 and 25 mN m-1 for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB film made in the gas phase show domains with a size of about 200 A diameter and 70 A height. However, the LB films made in the solid phase show a very smooth surface with 2 A surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below 105 V cm-1 and the calculated electrical conductivity is about 10-13 S cm-1. Nonohmic conduction has been observed above = 10-11 V cm and the conduction mechanism can be explained by the Schottky effect.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1125-1128
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• 2002

Tantalum pentoxide (Ta$_2$O$\sub$5/) is a candidate for use in metal-insulator-metal diode in switching devices for active-matrix liquid-crystal displays. The MIM diode with very low threshold voltage and perfect symmetry was fabricated. High quality Ta$_2$O$\sub$5/ thin films were obtained by using an anodizing method. Rutherford backscattering spectroscopy, transmission electron microscope observations, auger electron spectroscopy, ellipsometry measurements, and electrical measurements, such as current - voltage(I-V) measurements were performed to investigate Ta$_2$O$\sub$5/ films and their reliability and indicated that the obtained TaOx thin films were reliable Ta$_2$O$\sub$5/ films for the applications. Furthermore, in this paper, we discuss the effects of top-electrode metals and annealing conditions. The conduction mechanism of the leakage current and the symmetry characteristics related to the Schottky emission and Poole-Frankel effect are also discussed using the results of electrical measurements and conduction barrier theory.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.41-46
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• 2002

In this work, we studied electrical characteristics and leakage current mechanism of Au/$Ta_2O_5$/Si metal-oxide-semiconductor (MOS) devices. $Ta_2O_5$ thin film (63nm) was deposited by atomic layer deposition (ALD) method at temperature of $235^{\circ}C$. The structures of the $Ta_2O_5$ thin films were examined by X-Ray Diffraction (XRD). From XRD, the structure of $Ta_2O_5$ was single phase and orthorhombic. From capacitance-voltage (C-V) analysis, the dielectric constant was 19.4. The temperature dependence of current-voltage (I-V) characteristics of $Ta_2O_5$ thin film was studied from 300 to 423 K. In ohmic region (<0.5 MVcm${-1}$), the resistivity was $2.4056{\times}10^{14}({\Omega}cm)$ at 348 K. The Schottky emission is dominant in lower temperature range from 300 to 323 K and Poole-Frenkel emission dominant in higher temperature range from 348 to 423 K.

• The Korean Journal of Ceramics
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• v.2 no.2
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• pp.95-101
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• 1996

Variations of the leakage current behaviors and interface potential barrier $({\Phi}_B)$ of rf-sputter deposited (Ba, Sr)$TiO_3$ (BST) thin films with thicknesses ranging from 20 nm to 150nm are investigated as a function of the thickness and bias voltages. The top and bottom electrodes are dc-sputter-deposited Pt films. ${\Phi}_B$ critically depends on the BST film deposition temperature, postannealing atmosphere and time after the annealing. The postannealing under $N_2$ atmosphere results in a high interface potential barrier height and low leakage current. Maintaining the BST capacitor in air for a long time reduces the ${\Phi}_B$ from about 2.4 eV to 1.6 eV due to the oxidation. ${\Phi}_B$ is not so dependent on the film thickness in this experimental range. The leakage conduction mechanism is very dependent on the BST film thickness; the 20 nm thick film shows tunneling current, 30 and 40 nm thick films show Shottky emission current.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.9
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• pp.502-509
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• 2000

In this paper in order to evaluat quantitavely the formation mechanism of space charge and its effects on the conduction characteristics in LDPE we have carried out the numerical analysis on the basis of experimental results of space charge distribution cathode field and current with time which had been simultaneously measured at applied field of 50kV/mm and room temperature. As the models for numerical analysis we employ the Richarson-Schottky theory for charge injection from electrode into LDPE and the band-tail conduction at crystalline regions and the hopping conduction by traps which mainly exist at the interface regions of crystalline-amorphous region for charge transport in LDPE. Futhermore in order to investigate the influence of physical parameters on the time characteristcs of space charge distribution and measured current we have changed the values of trap density activation energies for charge injection and transport and have analyzed their effects.