Platinum Silicide/n-Silicon Photoelectrodes: Dependence on the Conditions of 'Platinum Silicide' Formation

Abstract

The photoelectrochemical efficiency and ideality of platinum silicide /n-silicon (1 1 1 ) electrodes were investigated for dependence on silicide growth parameters. A thermal fabrication process was chosen and variation to the following three variables was made individually: the thickness of the deposited platinum, the reaction temperature and the reaction time.

The silicide surface layers investigated were PtSi , Pt₂Si, and combinations of these compounds, in a single thermally grown product layer. The electrode efficiency was found to be most dependent upon the thickness of the silicide layer, increasing with layer thickness over the range studied, from 5 to 75 nm. Sputtering of the surface with 4 keV argon ions was found to reduce the photoelectrochemical response to a very low level. Solid state photocells could be constructed with efficiencies similar to the photoelectrochemical devices. These cells were also affected by sputtering the surface. For sputtered samples, both in solution and solid state, white light illumination produced a larger photocurrent than a He/ Ne laser. Shining a laser onto the sample when illuminated with white light reduced the photocurrent, indicating that the sputtering altered the silicon near the silicide interface.

Corrosion measurements produced Tafel corrosion rates of a low magnitude, near 10^-2 mpy .