Abstract: The Mg-Sn coatings were synthesized by magnetron co-sputtering of oxygen containing Mg-Sn and Mg targets on Si-substrate for fabrication of pyroelectric sensor.The effect of the sputtering cycles,wherein 210 s for Mg-Sn and 30 s for Mg, on the microstructures and electrical conductivity was investigated with X-ray diffraction,scanning electron microscopy and X-ray photoelectron spectroscopy and.The preliminary results show that the cycle-number had a major impact.To be specific,a decreasing depth-profile of Mg1s peak,from 1286 to 1285 eV,was observed; as the cycle-number increased from 2,000 to 6,000 cycles,the Sn-and O-contents increased and the Mg-content decreased,resulting in a decrease of the conductivity.Moreover,a decrease of Mg₂Sn-content,accompanied by an increase of Sn-content,was found to decrease the mobility,because the carrier concentration decreased in the p-typed semiconducting Mg-Sn coatings.