In this paper oxygen sensor based on gallium oxide thin films has been analyzed. The gallium oxide thin films were prepared by rf magnetron sputtering from a powder target using Ar as the sputtering gas. The sensing characteristics (stability, sensitivity and response time) of the oxygen sensor were investigated at 1000 degrees C. At high temperatures gallium oxide thin films behaves like an n-type semiconductor due to an oxygen deficit. The thin films obtained by this method have a higher electrical conductivity due to a higher oxygen vacancy concentration. Two sensors with different geometries were investigated, one using interdigital electrodes and one using a sandwich structure with a mesh type electrode on the top. Response times of about 14 s can be achieved for low oxygen concentrations using first type sensor and about 27 s for the second type. The mechanism of oxygen sensing in sputtered gallium oxide films is also discussed. (c) 2005 Elsevier B.V. All rights reserved.