Electron migration behavior of Au/Cu multilayer films on Si substrates under UV radiation

Au/Cu multilayer films were plated by the magnetron sputtering method on p-Si(100) substrates. The sample temperature was changed from room temperature to 44 °C under UV radiation in a vacuum within 120 minutes, and then remained stable with treatment time increased. Meanwhile, the surface roughness was changed from 4.2 nm to 5.9 nm and then also remained stable. But the interface width of Au/Cu still continued to increase during that steady stage. The calculation results show that the concentration gradient of Cu atoms fell to 2.24 in 360 minutes from 3.45 at the beginning. The increase of defects in the grain boundaries of the Au layer was induced by UV radiation, because the Cu element had a smaller work function relative to the Au element and it was more likely to migrate to the surface layer through the grain boundaries of the Au layer.