• Korean Journal of Materials Research
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• v.26 no.2
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• pp.84-89
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• 2016

We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to $200^{\circ}C$. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as $100^{\circ}C$ and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.25-29
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• 1999

We have developed a laser molecular beam epitaxy system for the layer-by-layer growth of oxide thin films. Using this system, we could grow and control oxide thin films of LaAlO$_3$in a molecular layer epitaxy mode on the atomically flat SrTiO$_3$ substrate with a LaAlO$_3$single crystal target. Very clear RHEED oscillations were observed during to growth of a LaAlO$_3$ film for a long period under the optimized conditions of substrate temperature at $650^{\circ}C$, oxygen pressure at 1$\times$10\ulcorner torr, and an incident laser fluence of 4.6J/$\textrm{cm}^2$. The height of mono-layer-LaAlO$_3$ film grown during one period of RHEED intensity oscillation was 3.8$\AA$.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.250-252
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• 2017

High-performance full swing logic inverters were fabricated using amorphous 1 wt% Si doped indium-zinc-oxide (a-SIZO) thin films with different channel layer thicknesses. In the inverter configuration, the threshold voltage was adjusted by varying the thickness of the channel layer. The depletion mode (D-mode) device used a TFT with a channel layer thickness of 60 nm as it exhibited the most negative threshold voltage (-1.67 V). Inverters using enhancement mode (E-mode) devices were fabricated using TFTs with channel layer thicknesses of 20 or 40 nm with excellent subthreshold slope (S.S). Both the inverters exhibited high voltage gain values of 30.74 and 28.56, respectively at $V_{DD}=15V$. It was confirmed that the voltage gain can be improved by increasing the S.S value.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.16.1-16.1
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• 2009

We have fabricated solution processed oxide semiconductor active layer for thin film transistors (TFTs). The oxide semiconductor layers were prepared by ink-jet printing the sol-gel precursor solution based on doped-ZnO. Inorganic ZnO-based thin films have drawn significant attention as an active channel layer for TFTs applications alternative to conventional Si-based materials and organic semiconducting materials, due to their wide energy band gap, optical transparency, high mobility, and better stability. However, in spite of such excellent device performances, the fabrication methods of ZnO related oxide active layer involve high cost vacuum processes such as sputtering and pulsed laser deposition. Herein we introduced the ink-jet printing technology to prepare the active layers of oxide semiconductor. Stable sol-gel precursor solutions were obtained by controlling the composition of precursor as well as solvents and stabilizers, and their influences on electrical performance of the transistors were demonstrated by measuring electrical parameters such as off-current, on-current, mobility, and threshold voltage. Microstructure and thermal behavior of the doped ZnO films were investigated by SEM, XRD, and TG/DTA. Furthermore, we studied the influence of the ink-jet printing conditions such as substrate temperature and surface treatment on the microstructure of the ink-jet printed active layers and electrical performance. The mobility value of the device with optimized condition was about 0.1-1.0 $cm^2/Vs$ and the on/off current ratio was about $10^6$. Our investigations demonstrate the feasibility of the ink-jet printed oxide TFTs toward successful application to cost-effective and mass-producible displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.314-317
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• 1997

The electrical and physical characteristics of aluminum oxide and Pt thin films on it, deposited by reactive sputtering and DC magnetron sputtering respectively, were analyzed with increasing annealing temperature(400~80$0^{\circ}C$) by four point probe, SEM and XRD. Under $600^{\circ}C$ of annealing temperature, aluminum oxide had the properties of improving Pt adhesion to SiO$_2$and insulation without chemical reaction to Pt thin films and the resistivity of Pt thin films was improved. But these properties of aluminum oxide and Pt thin films on it were degraded over $700^{\circ}C$ of annealing temperature because aluminum oxide was changed into metal aluminum and then reacted to Pt thin films deposited on it. In the analysis of the thermal charateristics of Pt micro-heater fabricated on Si07/si substrate, the temperature of Pt micro-heater is up to 41$0^{\circ}C$ with the power dissipation 1.8 watts.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.401-405
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• 2017

Because silicon thin film solar cells have a high absorption coefficient in visible light, they can absorb 90% of the solar spectrum in a $1-{\mu}m$-thick layer. Silicon thin film solar cells also have high transparency and are lightweight. Therefore, they can be used for building integrated photovoltaic (BIPV) systems. However, the contact electrode needs to be replaced for fabricating silicon thin film solar cells in BIPV systems, because most of the silicon thin film solar cells use metal electrodes that have a high reflectivity and low transmittance. In this study, we replace the conventional aluminum top electrode with a transparent aluminum-doped zinc oxide (AZO) electrode, the band level of which matches well with that of the intrinsic layer of the silicon thin film solar cell and has high transmittance. We show that the AZO effectively replaces the top metal electrode and the bottom fluorine-doped tin oxide (FTO) substrate without a noticeable degradation of the photovoltaic characteristics.

• Transactions on Electrical and Electronic Materials
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• v.12 no.6
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• pp.267-270
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• 2011

In the process of inkjet-printed zinc tin oxide thin-film transistor, the effect of metallic interlayer underneath of source and drain electrode was investigated. The reason for the improved electrical properties with thin molybdenum oxide ($MoO_3$) layer was due to the chemically intermixed state of metallic interlayer, aluminum source and drain, and oxide semiconductor together. The atomic configuration of three Mo $3d_3$ and $3d_5$ doublets, three different Al 2p core levels, two Sn $3d_5$, and four different types of oxygen O 1s in the interfaces among those layers was confirmed by X-ray photospectroscopy.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.3
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• pp.33-39
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• 1983

New Schottky devices with thin stepped oxide layer (about 1000 ${\AA}$) along the edge of metal-semiconductor junction have been designed and fabricated. The breakdown voltages of these diodes have been compared with those of conventional metal overlap and P guard ring Schottky diode structures. Thin stepped oxide layer has been grown by the process of T.C.E. oxidation. In order to compare and demonstrate the improved down phenomena of these devices, conventional metal overlap diode and P guard ring which have the same dimension with new devices have also been integrated in a same New Schottty devices structured with thin stepped oxide layer have shown significant improvement in breakdown phenomena compared with conventional diodes.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.81-86
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• 2020

MoO₃ metal oxide nanostructure was formed by hydrothermal synthesis, and a perovskite solar cell with an MoO₃ hole transfer layer was fabricated and evaluated. The characteristics of the MoO₃ thin film were analyzed according to the change of hydrothermal synthesis temperature in the range of 100 ℃ to 200 ℃ and mass ratio of AMT : nitric acid of 1 : 3 ~ 15 wt%. The influence on the photoelectric conversion efficiency of the solar cell was evaluated. Nanorod-shaped MoO₃ thin films were formed in the temperature range of 150 ℃ to 200 ℃, and the chemical bonding and crystal structure of the thin films were analyzed. As the amount of nitric acid added increased, the thickness of the thin film decreased. As the thickness of the hole transfer layer decreased, the photoelectric conversion efficiency of the perovskite solar cell improved. The maximum photoelectric conversion efficiency of the perovskite solar cell having an MoO₃ thin film was 4.69 % when the conditions of hydrothermal synthesis were 150 ℃ and mass ratio of AMT : nitric acid of 1 : 12 wt%.

• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.43-49
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• 2014

Zinc-tin oxides (ZTO) thin film transistors have been fabricated at different process pressure via re sputtering technique. TFT properties were improved by depositing channel layers at lower pressure. From the analysis of TFTs comprised of multi layer channel, deposited consecutively at different sputtering pressure, it was suggested that the electrical characteristics of TFTs were mainly affected by interfacial layer due to their high conductance, however, the stability under the NBIS condition was influenced by whole bulk layer due to low concentration of positive charges, which might be generated by the oxygen vacancy transition, from Vo0 to $Vo^{2+}$. Those improvements were attributed to increasing sputtered target atoms and decreasing harmful effects of oxygen molecules by adopting low sputtering pressure condition.