• Korean Journal of Materials Research
• /
• v.19 no.9
• /
• pp.473-480
• /
• 2009

In order to provide the mechanism of nozzle clogging, recovered nozzles for high strength steel grade were examined carefully after continuous casting. The thickness of clogged material in SEN is increased in the following order: from the bottom to the top of the nozzle, upper part of slag line, and the pouring hole. Nozzle clogging material begins to form due the adhesion of metal to nozzle wall, the decarburization, and reduction of oxide in the refractory by Al and Ti in the melt. The reduction of oxide in the refractory by Al and Ti improves the wettability of the melt on the refractory and forms a thin Al-Ti-O layer. Metal containing micro alumina inclusions is solidified on the Al-Ti-O layer, and the solid layer grows due to the heat evolution through the nozzle wall. Thermodynamic calculation has been made for the related reactions. The effect of superheat to the nozzle clogging is discussed on ultra low carbon steel and low carbon steel.

• Electronics and Telecommunications Trends
• /
• v.5 no.1
• /
• pp.55-70
• /
• 1990

SIMOX SOI is known to be one of the most useful technologies for fabrications of new generation ULSI devices. This paper describes the current status of SIMOX SOI technology for ULSI applications. The SIMOX wafer is vertically composed of buried oxide layer and silicon epitaxial layer on top of the silicon substrate. The buried oxide layer is used for the vertical isolation of devices The oxide layer is formed by high energy ion implantation of high dose oxygen into the silicon wafer, followed by high temperature annealing. SIMOX-based CMOS fabrication is transparent to the conventional IC processing steps without well formation. Furthermore, thin film CMOX/SIMOX can overcome the technological limitations which encountered in submicron bulk-based CMOS devices, i.e., soft-error rate, subthreshold slope, threshold voltage roll-off, and hot electron degradation can be improved. SIMOX-based bipolar devices are expected to have high density which comparable to the CMOX circuits. Radiation hardness properties of SIMOX SOI extend its application fields to space and military devices, since military ICs should be operational in radiation-hardened and harsh environments. The cost of SIMOX wafer preparation is high at present, but it is expected to reduce as volume increases. Recent studies about SIMOX SOI technology have demonstrated that the performance of the SIMOX-based submicron devices is superior to the circuits using the bulk silicon.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.8
• /
• pp.484-490
• /
• 2017

We investigated the rewritable operation of a non-volatile memory device composed of Al (top)/$TiO_2$/indium-zinc-oxide (IZO)/Al (bottom). The oxygen-deficient IZO layer of the device was spin-coated with 0.1 M indium nitrate hydrate and 0.1 M zinc acetate dehydrate as precursor solutions, and the $TiO_2$ layer was fabricated by atomic layer deposition. The oxygen vacancies IZO layer of an active component annealed at $400^{\circ}C$ using thermal annealing and it was proven to be in oxygen vacancies and oxygen binding environments with OH species and heavy metal ions investigated by X-ray photoelectron spectroscopy. The device, which operates at low voltages (less than 3.5 V), exhibits non-volatile memory behavior consistent with resistive-switching properties and an ON/OFF ratio of approximately $3.6{\times}10^3$ at 2.5 V.

• Nuclear Engineering and Technology
• /
• v.42 no.4
• /
• pp.434-441
• /
• 2010

The activation products of aluminum and argon are key radionuclides for operational and environmental radiological safety during the normal operation of open-tank-in-pool type research reactors using aluminum-clad fuels. Their activities measured in the primary coolant and pool surface water of HANARO have been consistent. We estimated their sources from the measured activities and then compared these values with their production rates obtained by a core calculation. For each aluminum activation product, an equivalent aluminum thickness (EAT) in which its production rate is identical to its release rate into the coolant is determined. For the argon activation calculation, the saturated argon concentration in the water at the temperature of the pool surface is assumed. The EATs are 5680, 266 and 1.2 nm, respectively, for Na-24, Mg-27 and Al-28, which are much larger than the flight lengths of the respective recoil nuclides. These values coincide with the water solubility levels and with the half-lives. The EAT for Na-24 is similar to the average oxide layer thickness (OLT) of fuel cladding as well; hence, the majority of them in the oxide layer may be released to the coolant. However, while the average OLT clearly increases with the fuel burn-up during an operation cycle, its effect on the pool-top radiation is not distinguishable. The source of Ar-41 is in good agreement with the calculated reaction rate of Ar-40 dissolved in the coolant.

• Corrosion Science and Technology
• /
• v.21 no.3
• /
• pp.200-208
• /
• 2022

Aluminum alloy is used by adding various elements according to the needs of the industry. Aluminum alloys such as 5052 and 6061 are known to possess excellent corrosion resistance by adding Mg. Despite their excellent physical properties, corrosion can occur. To solve this problem, an anodization technique generally can improve corrosion resistance by forming an oxide structure with maximized hydrophobic properties through coatings. In this study, the anodizing technique was used to improve the hydrophobicity of aluminum 5052 and 6061 by creating porous nanostructures on top of the surface. An oxide film was formed by applying anodizing voltages of 20, 40, 60, 80, and 100 V to aluminum alloys followed by immersion in 0.1 M phosphoric acid for 30 minutes to expand oxide pores. Contact angle and corrosion characteristics were different according to the structure after anodization. For the 5052 aluminum, the corrosion potential was improved from -363 mV to -154 mV as the contact angle increased from 116° to 136°. For the 6061 aluminum, the corrosion potential improved from -399 mV to -124 mV when the contact angle increased from 116° to 134°.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.344-344
• /
• 2014

Transparent amorphous oxide semiconductors such as a In-Ga-Zn-O (a-IGZO) have advantages for large area electronic devices; e.g., uniform deposition at a large area, optical transparency, a smooth surface, and large electron mobility >10 cm2/Vs, which is more than an order of magnitude larger than that of hydrogen amorphous silicon (a-Si;H).1) Thin film transistors (TFTs) that employ amorphous oxide semiconductors such as ZnO, In-Ga-Zn-O, or Hf-In-Zn-O (HIZO) are currently subject of intensive study owing to their high potential for application in flat panel displays. The device fabrication process involves a series of thin film deposition and photolithographic patterning steps. In order to minimize contamination, the substrates usually undergo a cleaning procedure using deionized water, before and after the growth of thin films by sputtering methods. The devices structure were fabricated top-contact gate TFTs using the a-IGZO films on the plastic substrates. The channel width and length were 80 and 20 um, respectively. The source and drain electrode regions were defined by photolithography and wet etching process. The electrodes consisting of Ti(15 nm)/Al(120 nm)/Ti(15nm) trilayers were deposited by direct current sputtering. The 30 nm thickness active IGZO layer deposited by rf magnetron sputtering at room temperature. The deposition condition is as follows: a rf power 200 W, a pressure of 5 mtorr, 10% of oxygen [O2/(O2+Ar)=0.1], and room temperature. A 9-nm-thick Al2O3 layer was formed as a first, third gate insulator by ALD deposition. A 290-nm-thick SS6908 organic dielectrics formed as second gate insulator by spin-coating. The schematic structure of the IGZO TFT is top gate contact geometry device structure for typical TFTs fabricated in this study. Drain current (IDS) versus drain-source voltage (VDS) output characteristics curve of a IGZO TFTs fabricated using the 3-layer gate insulator on a plastic substrate and log(IDS)-gate voltage (VG) characteristics for typical IGZO TFTs. The TFTs device has a channel width (W) of $80{\mu}m$ and a channel length (L) of $20{\mu}m$. The IDS-VDS curves showed well-defined transistor characteristics with saturation effects at VG>-10 V and VDS>-20 V for the inkjet printing IGZO device. The carrier charge mobility was determined to be 15.18 cm^2 V-1s-1 with FET threshold voltage of -3 V and on/off current ratio 10^9.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.5
• /
• pp.526-532
• /
• 2015

We quantitatively investigated instability mechanisms under simultaneous positive gate and drain bias stress (SPGDBS) in self-aligned top-gate amorphous indium-zinc-oxide thin-film transistors. After SPGDBS ($V_{GS}=13V$and $V_{DS}=13V$), the parallel shift of the transfer curve into a negative $V_{GS}$ direction and the increase of on current were observed. In order to quantitatively analyze mechanisms of the SPGDBS-induced negative shift of threshold voltage (${\Delta}V_T$), we experimentally extracted the density-of-state, and then analyzed by comparing and combining measurement data and TCAD simulation. As results, 19% and 81% of ${\Delta}V_T$ were taken to the donor-state creation and the hole trapping, respectively. This donor-state seems to be doubly ionized oxygen vacancy ($V{_O}^{2+}$). In addition, it was also confirmed that the wider channel width corresponds with more negative ${\Delta}V_T$. It means that both the donor-state creation and hole trapping can be enhanced due to the increase in self-heating as the width becomes wider. Lastly, all analyzed results were verified by reproducing transfer curves through TCAD simulation.

• Journal of the Korean Vacuum Society
• /
• v.17 no.2
• /
• pp.156-159
• /
• 2008

The electrical characteristic of SiGe-on-SOI (SGOI) wafer with different Ge concentration were evaluated by pseudo-MOSFET. Epitaxial SiGe layers was grown directly on top of SOI with Ge concentrations of 16.2, 29.7, 34.3 and 56.5 at.%. As Ge concentration increased, leakage current increased and threshold voltage shifted from 3 V to 7 V in nMOSFET, from -7 V to -6 V in pMOSFET. The interface states between buried oxide and top of Si was significantly increased by the rapid thermal annealing (RTA) process, and so the electrical characteristic of SGOI wafer degraded. On the other hand, additional post RTA　annealing (PRA) showed that it was effective in decreasing the interface states generated by RTA processes and the electrical characteristic of SGOI wafer enhanced higher than initial state.

• ETRI Journal
• /
• v.31 no.6
• /
• pp.660-666
• /
• 2009

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top-gate In-Ga-Zn-oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below $200^{\circ}C$, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as $Si_3N_4$ and $Al_2O_3$, the electrical properties are analyzed. After post-annealing at $200^{\circ}C$ for 1 hour in an $O_2$ ambient, the sub-threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative-bias stress tests on TFTs with a $Si_3N_4$ IDL, the degradation sources are closely related to unstable bond states, such as Si-based broken bonds and hydrogen-based bonds. From constant-current stress tests of $I_d$ = 3 ${\mu}A$, an IGZO-TFT with heat-treated $Si_3N_4$ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge-injection and electron-trapping behavior.

• Journal of Environmental Science International
• /
• v.19 no.6
• /
• pp.715-735
• /
• 2010

This study is designed to assess the priority order of the chemicals to cause to generate occupational diseases in order to understand the fundamental data required for the preparation of health protective measure for the workers dealing with chemicals. The 41 types of 51 ones of chemicals to cause to generate the national occupational diseases were selected as the study objects by understanding their domestic use or not, and their occupational diseases' occurrence or not among 110,608 types of domestic and overseas chemicals. To assess their priority order the sum of scores was acquired by understanding the actually classified condition based on a perfect score of physical riskiness(90points) and health toxicity(92points) as a classification standard by GHS, the priority order on GHS riskiness assessment, GHS toxicity assessment, GHS toxic xriskiness assessment(sum of riskiness plus toxicity) was assessed by multiplying each result by each weight of occupational disease's occurrence. The high ranking 5 items of chemicals for GHS riskiness assessment were turned out to be urethane, copper, chlorine, manganese, and thiomersal by order. Besides as a result of GHS toxicity assessment the top fives were assessed to be aluminum, iron oxide, manganese, copper, and cadium(Metal) by order. On the other hand, GHS toxicity riskiness assessment showed that the top fives were assessed to be copper, urethane, iron oxide, chlorine and phenanthrene by order. As there is no material or many uncertain details for physical riskiness or health toxicity by GHS classification though such materials caused to generate the national occupational diseases, it is very urgent to prepare its countermeasure based on the forementioned in order to protect the workers handling or being exposed to chemicals from health.