CO SENSORS BASED ON COPPER-DOPED, ZIRCONIA-DOPED AND UNDOPED ZINC OXIDE THIN FILMS

M.T. Alejos-Palomares, M. de L. Olvera, A. Maldonado

CINVESTAV (SEES) DEPARTAMENTO DE INGENIERÍA ELÉCTRICA-SEES

Av. Instituto Politécnico Nacional 2508 Col. San Pedro Zacatenco. 07300, México, D.F.

Some oxide semiconductors change their electrical properties due to the adsorption of toxic and combustible gases on their surfaces. Zinc oxide thin films have been studied for an application as CO sensor. Films were deposited by a simple chemical spray method. The started solution was zinc acetate plus water, alcohol and acetic acid; zirconia pentanedionate and copper chloride were added for doped zinc oxide films. The molarities solution were 0.05 M and 0.1 M; substrate temperatures were 400 and 450 ° C and the growth time was varied in order to obtain the thickness film expected. The films were electrically characterized as a function of carbon monoxide concentration and temperature in a controlled ambient. The temperature was varied from 100 to 400 ° C and the CO concentration was varied from 3 to 30 Torr. The sensitivity was computed by the relation S=[R(CO)-R(empty)]/R(empty), S is close to 1.00 in the best samples. The films with a good response (S» 1) were those with thickness ranged from 50 to 200 nm.