Jeong-Gyoo Kim

Gas sensing characteristics of Co 3 O 4 thick films with metal oxides

and -based thick films with additives such as (5 wt.%), (5 wt.%), (5 wt.%) and -ZnO(5 wt.%) were fabricated by screen printing method on alumina substrates. Their structural properties were examined by XRD and SEM. The sensitivities to iso-, , CO, and NO gases were investigated with the thick films heat treated at , and . From the gas sensing properties of the films, the films showed p-type semiconductor behaviors. (5 wt.%) thick film heat treated at showed higher sensitivity to i- and CO gases than other thick-films. (5 wt.%) thick film heat treated at showed the sensitivity of 170 % to 3000 ppm iso- gas and 100 % to 100 ppm CO gas at the working temperature of . The response time to i- and CO gases showed rise time of about 10 seconds and fall time of about minutes. The selectivity to i- and CO gases was enhanced in the (5 wt.%) thick film.

Ammonia Gas-sensing Characteristics of Cr 2 O 3 Thick Films

thick films were fabricated by screen printing method on alumina substrates and annealed at , , and in air, respectively. Structural properties examined by XRD and SEM showed (116) dominant peak and increased grain sizes with the annealing. The resistance of the films decreased with increasing the annealing temperature. Gas sensing characteristics to , CO, , and NO gases showed sensitivity only to gas. thick films annealed at had the sensitivity of about 15 % for 100 ppm gas at the working temperature of . The thick films had good selectivity to the gas. The response time to gas was about 10 seconds.

Effects of Substrate Temperature on Structural and Electrical Properties of α-Fe 2 O 3 Films Prepared by Ultrasonic Spray Pyrolysis

films were prepared by ultrasonic spray pyrolysis (USP) on coated Si wafers using iron acetylacetonate as an iron precursor. The crystallographic properties and surface morphologies of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray photoelectron spectroscopy (XPS) was carried out to determine the Fe oxidation states. In order to observe stability of the films to temperature, the resistance variation of the films with an ambient temperature was measured. The effects of substrate temperature on the structural and electrical properties of the films were studied. The films were densified from the substrate temperature of . The grain size of the films grown at was shown to be increased abruptly comparing with that of . The films showed a low resistance variation between the ambient temperature of and .

Ammonia gas sensing characteristics of LaFeO 3 thick-films With Al 2 O 3 additives

-based thick films with 2wt.%, 5wt.% and 10wt.% additives were fabricated by screen printing method on substrates. Structural, electrical and ammonia gas sensing characteristics of the thick films with different heat treatment temperatures were examined. From XRD results, the compound of and was not found until the heat treatment at . SEM microphotograph showed similar grain growth despite the amount of additives with the heat treatment. Thick films with high activation energy and low resistance in the electrical properties showed high sensitivity for gases. Thick films with 2wt % additives heat-treated at showed the sensitivities of 210% for 100 ppm gas at the working temperature of . The thick films showed food selectivity to gas.