• Proceedings of the KIEE Conference
• /
• 2001.11a
• /
• pp.168-170
• /
• 2001

The NiCr is an important material for present thin-film resistor application owing to its low TCR and thermal stability. In this work, the NiCr thin films were deposited on corning glass substrate by reactive magnetron sputtering and the annealing at temperatures range from 300 to $500^{\circ}C$ for 20 min in vacuum. X-ray, AFM, $R_s$(surface leakage current) have been used to study the structural and electrical properties of the NiCr thin films. The high precision NiCr thin films resistor with TCR(temperature coefficient of resistance) of less then 10 ppm/$^{\circ}C$ was obtained under in in-situ annealing at $300^{\circ}C$ on Cr buffer layer substrate. It is clear that the NiCr thin-films resistor electrical properties are low TCR related with it's annealing and buffer layer condition. NiCr thin film resistor having a good thermal stability and low TCR properties are expected for the application to the dielectric material of passive component.

• Applied Science and Convergence Technology
• /
• v.24 no.5
• /
• pp.184-189
• /
• 2015

We report a simple way to enhance the size gradient of an imprinted nanopattern through oxygen plasma etching under a nonuniform magnetic field. A sample substrate was placed next to a magnet, and then a nonuniform magnetic field condition was formed around the sample. Using oxygen plasma etching, a line pattern having an initial width of 273 nm was gradually modified from 248 nm at one end to 182 nm at the other end. Controlling the arrangement of the magnet and sample, we could induce a triangular shape size gradient. We verified that the gradually modified nanopatterns we produced are applicable to continual optical property control, showing a possibility to be utilized for optical components such as gratings and polarizers.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.9
• /
• pp.1520-1530
• /
• 1997

Machining pressed compacts of ceramic and WC-Co materials can be the most cost effective way of forming the bodies prior to sintering when the required number of pieces is small. In this study, in order to clarify the machinability for turning, the $Si_3N_4$ and the WC-Co green compacts unsintered were machined under different cutting conditions with various tools. Absorbing chips by vacuum hose decreases tool wear. The tool wear becomes larger in the order of the ceramic, CBN and cemented carbide tools in machining the $Si_3N_4$ green compacts. In machining the WC-Co green compacts, the tool wear becomes larger in the order of the ceramic, cemented carbide and CBN tools. The land of cutting edge does not affect tool wear. When machining with cemented carbide tool, the tool wear i equal cutting length is nearly identical in spite of the increase of cutting spee, and the roughness of machined surface was the best in the cutting speed of 90 m/min. The tool wear decreases with the increase of rake angle and relief angle and with the decrease of nose radius. The machined surfaces become worse with the increase of feed rate and depth of cut, and with the decrease of rake angle and relief angle. The tool wear is not affected by the feed and depth of cut.

• Journal of Surface Science and Engineering
• /
• v.50 no.3
• /
• pp.192-197
• /
• 2017

A 6-way-cross consisting of a 2.75-inch CF flange was used as a main chamber on a PFEIFFER VACUUM TMP station based on a 67 l / sec turbo molecular pump and a diaphragm pump to produce a magnet array with a volume ratio of 5.5: 1.A 1-inch diameter copper target and graphite target were fabricated using MDX-1.5K from Advanced Energy Industries, Inc as a DC power supply. Ion current density of copper target and graphite target was measured by unbalanced magnetron sputtering. The basic pressure condition was $6.3{\times}10^{-7}mbar$ and the process pressure was Ar 50 sccm at $1.0{\times}10^{-2}mbar$ (7.5 mTorr) in the Ar atmosphere. Therefore, the relative density of copper ions reaching the substrate with the measured ion current density was derived.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.194-197
• /
• 2005

Pulse-mode performance evaluation is made for a set of monopropellant hydrazine thrusters producing $0.95 lb_{f}$ of nominal steady-state thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test matrix, a typical data obtained from pulse-mode firing is given directly showing the variational behavior of propellant supply pressure, vacuum condition, and thrust, in addition to the thermal response of the thruster. The performance features are successfully compared to the reference criteria of 1-lbf standard monopropellant rocket engine.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.5
• /
• pp.483-490
• /
• 2008

Minimization of nozzle induces many flow losses in micro-propulsion system. In this study, we studied about thermal transpiration based micro propulsion system to overcome these losses. Thermal transpiration device(Knudsen pump) having no moving parts can self-pump the gaseous propellant by temperature gradient only (cold to hot). We designed, fabricated the Knudsen pump and analyzed pressure gradient efficiency of membrane according to Knudsen number under vacuum condition. Experimental results showed that thick membranes are more effective than thin membranes in transition flow regime, and pressure gradient efficiency according to Knudsen number is increased to maximum 82% apart from membrane thickness in free molecular regime.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.7
• /
• pp.308-314
• /
• 2005

The 2 GHz film bulk acoustic wave resonator(FBAR), one of the most necessary device of the next generation mobile communication system, consisted of solidly mounted resonator(SMR) structure using Brags reflector, was researched in this paper The FBAR applied SiO$_{2}$ and W had large difference of the acoustic impedance to reflector Al to electrode and ZnO to piezoelectric layer. Specially, the FBAR applied the two-step deposition method to improve the c-axis orientation and increase reproducibility of the fabrication device had good performance. The electrical properties of plasma such as impedance, resistance, reactance, $V_{pp},\;I{pp}$, VSWR and phase difference of voltage and current, was analyzed and measured by RF sensor with the variable experiment process factors such as gas ratio, RF power and base vacuum level about concerning the thickness, c-axis orientation, adhesion and roughness. The FBAR device about the optimum condition resulted reflection loss(S$_{11}$) of -17 dB, resonance frequency of 1.93 GHz, electric-mechanical coefficient(k$_{eff}$) of 2.38 $\%$ and Qualify factor of 580. It was seen better qualify than the common dielectric filter at present and expected on business to the filter device of 2 GHz bandwidth with the MMIC technology.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1349_1350
• /
• 2009

Thin films of pp(ST-Co-VA) were fabricated by plasma deposition polymerization (PVDPM) technique. Properties of the plasma polymerized pp(ST-Co-VA) thin films were investigated for application to semiconductor device as insulator. Thickness, dielectric property, composition of the pp(ST-Co-VA) thin films were investigated considering the relationship with preparation condition such as gas pressure and deposition time. In order to verify the possibility of application to organic thin film transistor, a pentacene thin film was deposited on the pp(ST-Co-VA) insulator by vacuum thermal evaporation technique. Crystalline property of the pentacene thin film was investigated by XRD and SEM, FT-IR. Surface properties at the pp(ST-Co-VA)/pentacene interface was investigated by contact angle measurement. The pp(ST-Co-VA) thin film showed a high-k (k=4.6) and good interface characteristic with pentacene semiconducting layer, which indicates that it would be a promising material for organic thin film transistor (OTFT) application.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.2
• /
• pp.262-267
• /
• 2008

Plasma immersion ion beam (PIIB) nitriding process is an environmentally benign and cost-effective process, and offers the potential of producing high dose of nitrogen ions in a way of simple, fast and economic technique for the high plasma flux treatment of large surface area with nitrogen ion source gas. In this report PIIB nitriding technique was used for nitriding on austenite stainless steel of AISI304 with plasma treatment at $250{\sim}500^{\circ}C$ for 4 hours, and with the working gas pressure of $2.67{\times}10^{-1}$ Pa in vacuum condition. This PIIB process might prove the advantage of the low energy high flux of ion bombardment and enhance the tribological or mechanical properties of austenite stainless steel by nitriding, Furthermore, PIIB showed a useful surface modification technique for the nitriding an irregularly shaped three dimensional workpiece of austenite stainless steel and for the improvement of surface properties of AISI 304, such as hardness and strength

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.58 no.4
• /
• pp.476-482
• /
• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.