• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.888-891
• /
• 2003

This paper describes on the fabrication and characteristics of micro ceramic thin-film type pressure sensors based on Ta-N strain-gauges for high-temperature applications. The Ta-N thin-film strain-gauges are deposited onto thermally oxidized Si diaphragms by RF sputtering in an argon-nitrogen atmosphere($N_2$ gas ratio: 8 %, annealing condition: $900^{\circ}C$, 1 hr.), Patterned on a wheatstone bridge configuration, and use as pressure sensing elements with a high stability and a high gauge factor. The sensitivity is $1.097{\sim}1.21mV/V.kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS. The fabricated pressure sensor presents a lower TCR, non-linearity than existing Si piezoresistive pressure sensors. The fabricated micro ceramic thin-film type pressure sensor is expected to be usefully applied as pressure and load sensors that is operable under high-temperature environments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1995.11a
• /
• pp.187-189
• /
• 1995

A Surface Acoustic Wave Gas sensor for NO, CO, H$_2$gas detection was designed fabricated, and tested. A delay line device was designed to composite a single mode SAW oscillator which enables to measure a SAW velocity. To reduce the effect of temperature and humidity, dual delay line oscillator circuit was used. And final output was measured by digital frequency counter. NO, CO, H$_2$gas were detected by WO$_3$thin film deposited on the path of the Delay Line.

• Korean Journal of Materials Research
• /
• v.18 no.2
• /
• pp.69-72
• /
• 2008

A sensor element array for combinatorial solution deposition research was fabricated using LTCC (Low-temperature Co-fired Ceramics). The designed LTCC was co-fired at $800^{\circ}C$ for 1 hour after lamination at $70^{\circ}C$ under 3000 psi for 30 minutes. $SnO_2$ sol was prepared by a hydrothermal method at $200^{\circ}C$ for 3 hours. Tin chloride and ammonium carbonate were used as raw materials and the ammonia solution was added to a Teflon jar. 20 droplets of $SnO_2$ sol were deposited onto a LTCC sensor element and this was heat treated at $600^{\circ}C$ for 5 hours. The gas sensitivity ($S\;=\;R_a/R_g$) values of the $SnO_2$ sensor and 0.04 wt% Pd-added $SnO_2$ sensor were measured. The 0.04 wt% Pd-added $SnO_2$ sensor showed higher sensitivity (S = 8.1) compared to the $SnO_2$ sensor (S = 5.95) to 200 ppm $CH_3COCH_3$ at $400^{\circ}C$.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1829-1832
• /
• 2008

This paper reports a novel gas sensing method by using a thermoelectric device, thermopile in this case, with an embedded tin oxide catalyst. By using a thin catalyst film, the response time and recovery time were remarkably improved. The fabricated gas sensor was characterized through detecting NOx gas with various concentrations.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.05a
• /
• pp.52.1-52.1
• /
• 2009

Cupric oxide (CuO) is a p-type semiconductor with band gap of ~1.7 eV and reported to be suitable for catalysis, lithium-copper oxide electrochemical cells, and gas sensors applications. The nanoparticles, plates and nanowires of CuO were found sensing to NO2, H2S and CO. In this work, we report about the comparison about hydrogen sensing of nano thin film and nanowires structured CuO deposited on single-walled carbon nanotubes (SWNTs). The thin film and nanowires are synthesized by deposition of Cu on different substrate followed by oxidation process. Nano thin films of CuO are deposited on thermally oxidized silicon substrate, whereas nanowires are synthesized by using a porous thin film of SWNTs as substrate. The hydrogen sensing properties of synthesized materials are investigated. The results showed that nanowires cupric oxide deposited on SWNTs showed higher sensitivity to hydrogen than those of nano thin film CuO did.

• Journal of Sensor Science and Technology
• /
• v.15 no.2
• /
• pp.120-126
• /
• 2006

Physicochemical and electrical properties for hydrogen gas sensors based on Pd-deposited $WO_3$ thin films were investigated as a function of Pd thickness, annealing temperature, and operating temperature. $WO_3$ thin films were deposited on an insulating material by thermal evaporator. XRD, FE-SEM, AFM, and XPS were used to evaluate the crystal structure, microstructure, surface roughness, and chemical property, respectively. The deposited films were grown $WO_3$ polycrystalline with rhombohedral structure after annealing at $500^{\circ}C$. The addition effect of Pd is not the crystallinity but the suppression of grain growth of $WO_3$. Pd was scattered an isolated small spherical grain on $WO_3$ thin film after annealing at $500^{\circ}C$ and it was agglomerated as an irregular large grain or diffused into $WO_3$ after annealing at $600^{\circ}C$. 2 nm Pd-deposited $WO_3$ thin films operated at $250^{\circ}C$ showed good response and recovery property.

• Journal of Sensor Science and Technology
• /
• v.14 no.2
• /
• pp.63-68
• /
• 2005

The nano-grained Pd or Pt-doped $SnO_{2}$ thin films were deposited on the alumina substrate at ambient temperature or $300^{\circ}C$ by using an R.F. magnetron sputtering system and then annealed at $650^{\cir}C$ for 1 hour or 4 hours in air. The crystallinity and microstructure of the annealed films were analyzed. A grain size of the thin films was 30 nm to 50 nm. As a result of gas sensitivity measurements to an alcohol vapor of $36^{\circ}C$, the 2 wt.% Pt-doped $SnO_{2}$ thin-film sensor deposited at $300^{\circ}C$ and annealed at $650^{\circ}C$ for 4 hours showed the highest sensitivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.471-474
• /
• 2000

A flat type microgas sensor was fabricated on the p-type silicon wafer with low stress S $i_3$ $N_4$, whose thickness is 2${\mu}{\textrm}{m}$ using MEMS technology and its characteristics were investigated. W $O_3$thin film as a sensing material for detection of N $O_2$gas was deposited using a tungsten target by sputtering method, followed by thermal oxidation at several temperatures (40$0^{\circ}C$~$600^{\circ}C$) for one hour. N $O_2$gas sensitivities were investigated for the W $O_3$thin films with different annealing temperatures. The highest sensitivity when operating at 20$0^{\circ}C$ was obtained for the samples annealed at $600^{\circ}C$. As the results of XRD analysis, the annealed samples had polycrystalline phase mixed with triclinic and orthorhombic structures. The sample exhibit higher sensitivity when the system has less triclinic structure. The sensitivities, $R_{gas}$ $R_{air}$ operating at 20$0^{\circ}C$ to 5 ppm N $O_2$of the sample annealed at $600^{\circ}C$ were approximately 90. 90.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03b
• /
• pp.19-19
• /
• 2010

We suggest CNT-based gas sensors for breath alcohol measurement. The sensors were composed of single-walled carbon nanotubes (SWNTs) thin film on glass substrate with simple process, and the SWNTs thin film as sensing layer was formed by multiple spray-coating with SWNT composites which was well-dispersed, highly controlled and differently functionalized by various binders (TEOS, MTMS, and VTMS) added in ethanol solvent. In this work, three different SWNTs thin films were made to compare their electrical response properties for alcohol vapor. From fabricated sensors, conductance responses were measured and discussed. In the result, our alcohol gas sensors showed an effective selectivity even at room temperature.

• Korean Journal of Materials Research
• /
• v.24 no.10
• /
• pp.532-537
• /
• 2014

In this study, highly sensitive hydrogen micro gas sensors of the multi-layer and micro-heater type were designed and fabricated using the micro electro mechanical system (MEMS) process and palladium catalytic metal. The dimensions of the fabricated hydrogen gas sensor were about $5mm{\times}4mm$ and the sensing layer of palladium metal was deposited in the middle of the device. The sensing palladium films were modified to be nano-honeycomb and nano-hemisphere structures using an anodic aluminum oxide (AAO) template and nano-sized polystyrene beads, respectively. The sensitivities (Rs), which are the ratio of the relative resistance were significantly improved and reached levels of 0.783% and 1.045 % with 2,000 ppm H2 at $70^{\circ}C$ for nano-honeycomb and nano-hemisphere structured Pd films, respectively, on the other hand, the sensitivity was 0.638% for the plain Pd thin film. The improvement of sensitivities for the nano-honeycomb and nano-hemisphere structured Pd films with respect to the plain Pd-thin film was thought to be due to the nanoporous surface topographies of AAO and nano-sized polystyrene beads.