Ferroelectric BaTiO3 thin films were fabricated by metalorganic chemical vapor deposition (MOCVD) at atmospheric pressure. The ultrasonic spraying technique has been used to carry the source materials. The common solutions of barium-diethylhexanoate and diisopropoxy-titanium-bis-acetylacetonate in n-butanol were used as the starting materials. Since the concentration of sources can be controlled in the common solution, this method is more simple and precise than other CVD processes. The films had (110) preferred orientation with increasing temperature. The dielectric constant (ε) and the loss factor (tan
δ) of thin film deposited at 550° C were about 250 and 0.1, respectively. The leakage current density was 10-5 A/cm2 at 0.1 MV/cm.
The H2S sensing characteristics of SnO2 thin films loaded with CuO were found to be much improved by reducing the film thickness. A 40-nm-thick film showed sensitivity as high as 20000 and 2000 to 1.5 and 0.3 ppm H
2
S in air, respectively, at 200° C, while the rate of response to 0.3 ppm H
2
S was rather slow.
The oxygen partial pressure dependence of current in CuOIZnO heterocontact has been investigated to confirm its humidity sensing mechanism. A CuO/ZnO heterocontact was fabricated by physically pressing the sintered disks of CuO and ZnO, and its current was measured at various oxygen partial pressures under wet and dry conditions at room temperature.The current of the heterocontact was strongly dependent on oxygen partial pressure only at forward bias and wet atmosphere. Such a phenomenon originates from the humidity sensing mechanism, i.e., electrolysis of water physisorbed at the vicinity of the heterocontact. The current measurement under air with ammonia water vapor also provided one more evidence for the electrolysis function of the heterocontact. gen partial pressure up to about 0.01 atm and then decreased smoothly. The maximum current change from the N2 to 02 atmosphere was large by about a factor of 100.
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