• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.91-91
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• 2009

In the past decade, Pd based thin films have been studied far hydrogen gas sensors due to their high possibility for energy industry and environmental applications. In this work, we report a navel method to fabricate highly sensitive hydrogen gas sensors based on PdO thin films. The films were deposited on Si substrates in Ar and $O_2$ ambient using reactive sputtering system. A semiconductor process has been utilized to fabricate PdO films with t=40nm. We observed the resistance changes of the PdO films with various $H_2$ concentrations. It was found that the electrical properties of the thin films depend on the composition of oxygen. The sensitivity is defined as $S\;=\;(R_0-R)/R{\times}100%$, where R and $R_0$ are the resistances in the presence of exposing the hydrogen gas and air, respectively. The sensitivity of the thin films was found to be as high as about 95%. After exposing to hydrogen gas, we discovered that the nano-sized cracks formed on the surface of the PdO thin films. The nano-cracks formed in deoxidized PdO thin films were known by playing a key role to reduce more than 4 times the response time of absorption. Our results illustrate that the deoxidized PdO thin films can be used as hydrogen sensors.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.347-352
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• 2010

This study reports a novel method off abricating highly sensitive hydrogen gas sensors based on PdO thin films. The PdO thin films with a thickness of 40 nm were deposited on Si substrates under Ar and $O_2$ ambient conditions using a reactive de magnetron sputtering system. Considerable changes in the resistance of the palladium oxide thin films were observed when they were initially exposed to hydrogen gas, as a result of the reduction process. The sensitivity of the PdO thin films was found to be as high as 90%. After the thin films were exposed to hydrogen gas, the nano-sized cracks were discovered to have formed on the surface of the PdO thin films. These types of nano-cracks that formed on the deoxidized PdO thin films are known to play a key role incausing a four-fold reduction of the response time of the absorption process. The results of this study demonstrate that deoxidized PdO thin films can be applied for use in the creation of high-sensitivity hydrogen sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.371-372
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• 2012

We have studied lead-based gapless semiconductors, $PbPdO_2$, which is very sensitive to external parameters such as temperature, pressure, electric field, etc[1]. We have fabricated pure $PbPdO_2$, Co- and Mn-doped $PbPdO_2$ thin films using the pulsed laser deposition. Because of the volatile element of Pb, it is very difficult to grow the films. Note that in case of $MgB_2$, Mg is also volatile element. So in order to enhance the quality of $MgB_2$, some experiments are carried out in annealing with Mg-rich atmosphere [2]. This annealing process with volatile element plays an important role in making smooth surface. Thus, we applied such process to our studies of $PbPdO_2$ thin films. As a result, we found the optimal condition of ex-situ annealing temperature ${\sim}650^{\circ}C$ and time ~12 hrs. The ex-situ annealing brought the extreme change of surface morphology of thin films. After ex-situ annealing with PbO-rich atmosphere, the grain size of thin film was almost 100 times enlarged for all the thin films and also the PbO impurity phase was smeared out. And from X-ray diffraction measurements, we determined highly crystallized phases after annealing. So, we measured electrical and magnetic properties. Because of reduced grain boundary, the resistivity of ex-situ annealed samples changed smaller than no ex-situ sample. And the carrier densities of thin films were decreased with ex-situ annealing time. In this case, oxygen vacancies were removed by ex-situ annealing. Furthermore, we will discuss the transport and magnetic properties in pure $PbPdO_2$, Co- and Mn-doped $PbPdO_2$ thin films in detail.

• Journal of the Korean Ceramic Society
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• v.30 no.9
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• pp.701-708
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• 1993

Pd-doped SnO2 thin films for hydrogen gas sensing were fabricated by reactive fo magnetron sputtering and were studied on effects of film thickness and Pd doping content. Pd doping caused the optimum sensor operation temperature to reduce down to ~25$0^{\circ}C$ and also enhanced gas sensitivity, compared with undoped SnO2 film. Gas sensitivity depended on the film thickness. The sensitivity increased with decreasing the film thickness, showing maximum sensitivities at the thickness of 730$\AA$ and 300~400$\AA$ for the undoped SnO2 and the Pd-doped SnO2 film, respectively. Further decrease of the film thickness beyond these thickness ranges, however, resulted in the reduction of sensitivity again.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1183-1191
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• 2001

The metallorganic chemical vapor deposition (MOCVD) method has been used to prepare TiO2 thin films for the degradation of hazardous organic compounds, such as 2-chlorophenol (2-CP). The effect of supporting materials and metal doping on the photocatalytic activity of TiO2 thin films also has been studied. TiO2 thin films were coated onto various supporting materials, including stainless steel cloth(SS), quartz glass tube (QGT), and silica gel (SG). Transition metals, such as Pd(II), Pt(IV), Nd(III) and Fe(III), were doped onto TiO2 thin film. The results indicate that Nd(Ⅲ) doping improves the photodegradation of 2-CP. Among all supporting materials studied, SS(37 ${\mu}m)$ appears to be the best support. An optimal amount of doping material at 1.0 percent (w/w) of TiO2-substrate thin film gives the best photodegration of 2-CP.

• Journal of Sensor Science and Technology
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• v.19 no.1
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• pp.58-61
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• 2010

This paper describes the fabrication and characteristics of NO sensor using ZnO thin film by RF magnetron sputter system. The sensitivity, working temperature, and response time of sputtered pure ZnO thin film and added catalysts such as Pt, Pd, Al, Ti on those films were measured and analyzed. The sensitivity of pure ZnO thin film at working temperature of $300^{\circ}C$ is 0.875 in NO gas concentration of 0.046 ppm. At same volume of the gas in chamber, measuring sensitivity of 1.87 at $250^{\circ}C$ was the case of Pt/ZnO thin film. The ZnO thin films added with catalyst materials were showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.101-106
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• 2008

The $SnO_2$ thin films doped with Pd and CNT as $NO_2$ gas sensor were prepared by spin coating and then the $NO_2$ gas response of these films were evaluated under $1ppm{\sim}5ppm\;NO_2$ concentration and operating temperature of $200^{\circ}C$. It was found that the sensor resistance was increased with $NO_2$ exposure and $NO_2$ concentration. The 3wt% Pd doped sample showed a sensitivity of 26.5 which was 10 times higher than that of pure $SnO_2$. And also the sensitivity of CNT doped sample increased with CNT content and it had 72 when 0.225 wt% of CNT was added under 5ppm $NO_2$ concentration.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1779-1781
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• 2000

Pd doped $SnO_2$ thin film sensors were prepared on alumina substrate by rf magnetron sputtering method. The sensitivity of thin film was investigated by varying the heat-treatment temperature, film thickness and gas species. The thin film heat-treated at 600$^{\circ}C$ and film thickness of 5000${\AA}$ showed the highest sensitivity at an operating temperature of 400$^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.175-176
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• 2007

This paper describes on the characteristics of Pd thin films deposited on poly-crystalline 3C-SiC buffer layers for microsensors, in which the poly 3C-SiC was grown on Si, $SiO_2$, and AlN substrates, respectively, by APCVD using HMDS, $H_2$, and Ar gas at $1100^{\circ}C$ for 30 min. In this work, a Pd thin film was deposited on the poly 3C-SiC film by RF magnetron sputter. The thickness, uniformity, and quality of these samples were evaluated by SEM. Crystallinity and orientation of the Pd film were analyzed by XRD. Finally, Pd/poly 3C-SiC schottky diodes were fabricated and characterized by current-voltage measurements. From these results, Pd/poly 3C-SiC devices are promising for high temperature hydrogen sensors and other microsensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.292-292
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• 2007

To apply PDP panel, Soda lime glass(SLG) is cheeper than Non-alkali glass and PD-200 glass but has problems such as low strain temperature and ion diffusion by alkali metal oxide. In this paper suggest the methode that prohibits ion diffusion by deposing barrier layer on SLG. Indium thin oxide(ITO) thin films and barrier layers were prepared on SLG substrate by Rf-magnetron sputtering. These films show a high electrical resistivity and rough uniformity as compared with PD-200 glass due to the alkali ion from the SLG on diffuse to the ITO film by the heat treatment. However these properties can be improved by introducing a barrier layer of $SiO_2\;or\;Al_2O_3$ between ITO film and SLG substrate. The characteristics of films were examined by the 4-point probe, SEM, UV-VIS spectrometer, and X-ray diffraction. GDS analysis confirmed that barrier layer inhibited Na and Ka ion diffusion from SLG. Especially ITO films deposited on the $Al_2O_3$ barrier layer had higher properties than those deposited on the $SiO_2$ barrier layer.