Illumination-Modulated Electrodeposition of Various Kinds of Noble Metal on p-Type Silicon

We report on the control of photo-assisted electrodeposition of several kinds of noble metal on p-type Si by adjusting the illumination condition. In the case of Pt and Cu, the deposition rate and the particle density of metal deposits under illumination were considerably higher than those obtained in the dark, because illumination produces photo-excited electrons and enables another channel through the conduction band for charge transfer in addition to the channel through the valence band which is used in the dark. Using this difference in deposition rate between these two conditions, we have succeeded in control of the morphology of Cu layer on p-type Si without changing applied potential, as well as the Pt system. The nucleation of metal particles could be controlled by modulating illumination duration and light intensity, and the nuclei could be grown in the dark. On the other hand, it was difficult to control the deposition of Pd and Au by modulating illumination, because they were spontaneously deposited even in the dark by their rapid immersion plating rate on p-type Si.