Examination of the CO/Pt/Cu layer structure with Kelvin probe and XPS analysis

Work function gas sensors are normally operating on the principle of potent ial difference measurements. In this work, the change of the work function (Delta Phi) of the Pt (< 1 nm )/Cu layer structure was studied in function of the sample's heat treatment temperature (23-300 degrees C) in response of 2000 ppm CO using a Kelvin p robe with a gold grid reference electrode. The aim of the heat treatment wa s the forming of the "proper size" Pt clusters by Pt diffusion. It was stud ied by XPS analysis. In each case it was found that the introduction of the CO decreases the wor k function by 6-55 mV at room temperature. The optimal heat treatment condi tions were determined, as 200 degrees C, 1 h, when the change of the work f unction was 9 mV beside 17 s response and recovery times. (C) 2000 Elsevier Science S.A. All rights reserved.