Synthesis and Characterization of Cu-Ag Alloy Coatings by Magnetron Co-Sputtering

The Cu-Ag alloy coatings,an electrical contact material,were synthesized by magnetron co-sputtering of Cu and Ag targets on substrates of lead-bronze,ceramics and glass.The sheet-resistance was measured with square resistance meter.The effect of the sputtering current of Ag-target and substrate bias voltage on roughness,thickness,Ag-content,microstructure and sheet-resistance was investigated with interferometer,scanning electron microscope and X-ray diffraction.The results show that the sputtering current and bias had a major impact.For example,as the current increased to above 0.5 A,the slowly increased Ag-content increased at a higher rate,accompanied by an increase of the thickness,and the sheet resistance decreased due to formation of the vertically penetrating columnar grains;as the bias increased,the sheet resistance and thickness decreased because the Cu-Ag coating,with decreasing defect-density and surface roughness,became increasingly more smooth and compact.Possible mechanisms were also tentatively discussed.