Polycrystalline silicon thin films grown by hot-wire chemical vapour deposition, using tungsten and tantalum as filament material, show different material properties. The different filament materials can cause this difference, due to different surface reactions and catalytic properties. X-Ray photoelectron spectroscopy on used-filaments shows a much lower silicon content in the near-surface region of the tantalum filaments, as compared to the tungsten ones. Furthermore, it is shown that the silicon content on the tungsten filament increases linearly with time, while the silicon content on the tantalum filament saturates quickly. A comparison of the silicon contents on the different filaments shows the possible presence of a liquid phase on the tungsten filament's surface during deposition. This liquid phase can cause the short lifetime of tungsten filaments compared to tantalum ones.