Gas microsensors based on semiconductor thin films of ZnO:Ga

Four carbon monoxide microsensor based on semiconducting oxide ZnO:Ga has been developed. The results and analysis of the characterization in an atmosphere containing carbon monoxide (CO), are presented in this work. dilution CO is 50ppm. ZnO:Ga thin films were deposited at 450 degrees C by the spray pyrolysis technique from a O.2 M starting solution with a [Ga]/[Zn]= 3 at. %. Microsensors with four different dimensions were designed: 20x20 mu m(2), 20x40 mu m(2), 20x60 mu m(2) and 100x100 mu m(2). Ohmic contacts were manufactured by thermal evaporation of aluminum on the top of the films. Both of gas microsensors and Al terminals were patterned by lift off. A surface resistance variation of several orders of magnitude was found in doped-gallium ZnO thin films when these were introduced into a camera with 0ppm, 1ppm, 5ppm, 50ppm and 100ppm of CO. Thin films gas microsensors were tested at several temperatures and different CO concentrations. The measurement temperatures employed were 200 degrees C, 250 degrees C and 300 degrees C. The surface of ZnO thin films doped with Ga was also characterized by AFM, showing a regular and uniform morpholgy.