• Korean Journal of Materials Research
• /
• v.5 no.2
• /
• pp.169-177
• /
• 1995

The diffusion barrier property of 100-nm-thick titanium nitride (TiN) film between Cu and Si was investigated using sheet resistance measurements, etch-pit observation, x-ray diffractometry, Auger electron spectroscopy, and transmission electron microscopy. The TiN barrier fails due to the formation of crystalline defects (dislocations) and precipitates (presumably Cu-silicides) in the Si substrate which result from the predominant in-diffusion of Cu through the TiN layer. In contrast with the case of Al, it is identified that the TiN barrier fails only the in-diffusion of Cu because there is no indication of Si pits in the Si substrate. In addition, it appears that the stuffing of TiN does not improve the diffusion barrier property in the Cu/TiN/Si structure. This indicates that in the case of Al, the chemical effect that impedes the diffusion of Al by the reaction of Al with $TiO_{2}$ which is present in the grain boundaries of TIN is very improtant. On the while, in the case of Cu, there is no chemical effect because Cu oxides, such as $Cu_{2}O$ or CuO, is thermodynamically unstable in comparison with $TiO_{2}$. For this reason, it is considered that the effect of stuffing of TiN on the diffusion barrier property is not significant in the Cu/ TiN/Si structure.

• Journal of IKEEE
• /
• v.11 no.4
• /
• pp.152-157
• /
• 2007

AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated and the effect of ${N_2}O$ plasma on the electrical characteristics of the devices was investigated. The HEMT exposed to ${N_2}O$ plasma formed by 40 W of RF power in a chamber with pressure of 20 mTorr at a temperature of $200^{\circ}C$, exhibited a reduction of gate leakage current from 246 nA to 1.2 pA by 10 seconds treatment. The current between the two isolated active regions reduced from 3 uA to 7 nA and the sheet resistance of the active layer was lowered also. The variations of electrical characteristics for HEMT were occurred within a short time expose of 10 seconds and the successive expose did not influence on the improvements of gate leakage characteristics and conductivity of the active region. The reduced leakage current level was not varied by successive $SiO_2$ deposition and its removal. The transconductnace and drain current of AlGaN/GaN HEMTs were increased also by the expose to the ${N_2}O$ plasma.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.302-305
• /
• 2009

This paper examines the effect of nitride formation on formability for Cu bearing high strength extra low carbon (ELC) steel sheets. For this purpose, we have investigated the effect of addition of aluminium (Al) and boron (B) on texture and precipitation behavior of the ELC steel during continuous annealing. Mechanical properties and microstructures of the ELC steel sheets were analyzed as well using uni-axial tensile test, electron back-scattered diffraction (EBSD) technique and transmission electron microscopy (TEM) following pilot rolling and continuous annealing. It has been found that the addition of Al and B increases the precipitation of AlN and BN. What is more, the scavange of solute nitrogen is effective in increasing the formability of the ELC steels. In addition, the Al and B addition improves the aging property of the ELC steel.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.4
• /
• pp.394-400
• /
• 2007

The properties and weldability of lap joints by PFSW with 1050 Al sheet was investigated according to tool shape. dimension and welding condition. Tensile shear test was carried out for lap jointed specimen, and the hardness in the joint regions was examined. Moreover interfacial joining length, metallograph and failure location of the lap-jointed cross section were discussed. Two tool types were a simple cylindrical type and a notched cylindrical type. Under joining conditions such as plunging depth of 2.2mm. rotating speed of 1600rpm and dwelling time of 3s, the tensile shear strength of lap-jointed specimen by the notched type tool was superior to that by simple cylindrical type tool. The maximum tensile shear load of lap jointed specimen was 5807N. Optimal dimensions of the notched type tool were as follows : diameters of the shoulder and pin were $18{\phi}mm$ and $10{\phi}mm$, and pin length was 2.2mm.

• Journal of IKEEE
• /
• v.17 no.1
• /
• pp.71-76
• /
• 2013

AlGaN/GaN HEMTs (High electron mobility transistors) with narrow channel were fabricated and the effect of channel scaling on the device were investigated. The devices were fabricated using e-beam lithography to have same channel length of $1{\mu}m$ and various channel width from 0.5 to $9{\mu}m$. The sheet resistance of the channel was increased corresponding to the decrease of channel width and the increase was larger at the width of sub-${\mu}m$. The threshold voltage of the HEMT with $1.6{\mu}m$ and $9{\mu}m$ channel width was -2.85 V. The transistor showed a variation of 50 mV at the width of $0.9{\mu}m$ and the variation 350 mV at $0.5{\mu}m$. The transconductance of 250 mS/mm was decreased to 150 mS/mm corresponding to the decrease of channel width. Also, the gate leakage current of the HEMT decreased with channel width. But the degree of was reduced at the width of sub-${\mu}m$. It was thought that the variation of the electrical characteristics of the HEMT corresponding to the channel width came from the reduced Piezoelectric field of the AlGaN/GaN structure by the strain relief.

• Current Photovoltaic Research
• /
• v.7 no.3
• /
• pp.61-64
• /
• 2019

In this study, we investigate organic-inorganic hybrid solar cells with a very simple three-layer structure (Al/n-Si/PEDOT:PSS). The performance of hybrid solar cells is optimized by controlling the sheet resistance and optical transmittance of the PEDOT:PSS layers. As the thickness of the PEDOT:PSS layer decreases, the optical absorption of the n-Si increases, which greatly improves the short-circuit current density ($J_{SC}$) of devices, but the increase in sheet resistance leads to a decrease in the open-circuit voltage ($V_{OC}$) and the fill factor (FF). The solar cell with the 180-nm thick PEDOT:PSS layer shows a highest efficiency of 8.45% ($V_{OC}$: 0.435 V, $J_{SC}$: $33.7mA/cm^2$, FF: 57.5%). Considering these results, it is expected that the optimizing process for the sheet resistance and transmittance of the PEDOT:PSS layer is essential for producing high-efficiency organic-inorganic hybrid solar cells and will serve as an important basis for achieving low-cost, high-efficiency solar cells.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.2 no.2
• /
• pp.95-102
• /
• 1994

Aluminum sheet application to automobile body panels has now become an important objective to meet the requirements of automobile weight reduction. As the Mg content in Al-Mg based alloys increased up to 7.19%, the strength and elongation increased. For instance. Al-7.19Mg alloy had a high strength of 305MPa and a high elongation of 35%. A study was also made to investigate the interrelation between grain size and tensile properties with varying the contents of Mg, Ti and Zr elements and annealing conditions. The yield stress decreased as the grain size increased, which increased the uniform elongation. The strain hardening exponents n increased as the Mg content increased, which depended on the increasing difficulties of the cross slip of dislocation.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1476-1478
• /
• 2002

In recent years, the tantalum nitride(TaN) thin-film has been developed for the electronic resistor, inductor and capacitor. In this papers, this study presents the surface profile and sheet-resistance property relationship of reactive-sputtered TaN thin film resistor processed by TaN(tantalum nitride) on alumina substrate. The TCR properties of the TaN films were discussed in terms of crystallization and thin films surface morphology due to annealing temperature. It is clear that the TaN thin-films resistor electrical properties are low TCR related with it's annealing temperature and ambient annealing condition. Respectively, at $300{\sim}400^{\circ}C$ on vacuum and nitrogen annealed thin film resistor having a goof thermal stability and lower TCR properties then as deposited thin films expected for the application to the dielectric material of passive component.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.5
• /
• pp.490-496
• /
• 2015

We have grown AlN/GaN heterostructure which is a promising candidate for mm-wave applications. For the growth of the high quality very thin AlN barrier, indium was introduced as a surfactant at the growth temperature varied from 750 to $1070^{\circ}C$, which results in improving electrical properties of two-dimensional electron gas (2DEG). The heterostructure with barrier thickness of 7 nm grown at of $800^{\circ}C$ exhibited best Hall measurement results; such as sheet resistance of $215{\Omega}/{\Box}$electron mobility of $1430cm^2/V{\cdot}s$, and two-dimensional electron gas (2DEG) density of $2.04{\times}10^{13}/cm^2$. The high electron mobility transistor (HEMT) was fabricated on the grown heterostructure. The device with gate length of $0.2{\mu}m$ exhibited excellent DC and RF performances; such as maximum drain current of 937 mA/mm, maximum transconductance of 269 mS/mm, current gain cut-off frequency of 40 GHz, and maximum oscillation frequency of 80 GHz.

• Transactions of Materials Processing
• /
• v.31 no.1
• /
• pp.11-16
• /
• 2022

In this paper, wear characteristics of PVD coatings were compared on the die surface for cold stamping of MART1470 steel sheet with the finite element analysis and the pin-on-disc wear test. Three types of PVD coatings (CrN, TiAlCrN, and MoS2TiCr(W)N) were considered for the tool surface made of STD11 material. The stamping process of an auto-body part was analyzed with the finite element method. Ranges of process variables for the wear test such as contact pressure, relative speed, and sliding distance were predicted from analysis results. In order to quantitatively analyze wear characteristics of each coating, the amount of wear was measured and compared according to process variables with the pin-on-disc wear test. The influence of each process variable was investigated and the wear characteristics of the three coating layers were quantitatively compared. It was confirmed that the wear characteristics of MoS₂TiCr(W)N coating were better than those of CrN and TiAlCrN. It was noted that the proposed prediction approach could predict and respond to the wear phenomenon occurring in the stamping process.