Abstract:The paper presents results concerning the effect of spatial inhomogeneous operating temperature on the gas discrimination power of a gas-sensor microarray, with the latter based on a thin SnO 2 film employed in the KAMINA electronic nose. Three different temperature distributions over the substrate are discussed: a nearly homogeneous one and two temperature gradients, equal to approx. 3.3 o C/mm and 6.7 o C/mm, applied across the sensor elements (segments) of the array. The gas discrimination power of the microarray is judged by using the Mahalanobis distance in the LDA (Linear Discrimination Analysis) coordinate system between the data clusters obtained by the response of the microarray to four target vapors: ethanol, acetone, propanol and ammonia. It is shown that the application of a temperature gradient increases the gas discrimination power of the microarray by up to 35 %.
Ion beam assisted deposition is applied to cover a gas sensor microarray of an electronic nose with an ultrathin gas-permeable SiO2 membrane varying in thickness across the array. Auger electron spectroscopy sputter depth profiles and non-Rutherford backscattering spectroscopy were used to study the uniformity of the deposition and the subsequent annealing step. The combination of spectroscopic ellipsometry for the freshly prepared membranes and line scans derived from Auger and angle resolved x-ray photoelectron spectroscopy, respectively, for the baked membrane is presented as a powerful quantification method for the determination of the desired SiO2 membrane thickness profiles.
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