I want to reach a different doping concentration of "Sulphur (S)" into TiO2 (thin films) by thermal or e-beam evaporation. Since, "S" has low melting point (about 115 Celsius) and it poisons the vacuum system. What is the best way to do this by PVD method?
There are sulphur sources commercially available - look for Veeco MBE operation!
Those evaporators are built up in two stages: In the first stage, molecular Sulfur is evaporated up to the equilibrium pressure (which will be substantially larger than your vacuum base pressure, therefore this cell is separated from the vacuum by a nozzle). The nozzle can be adjusted so that the wanted flux into the vacuum system can be regulated to the desired value. However, S does not evaporated monoatomically, but in S6- or S8-rings. Those have to be cracked in the second stage, typically be a heated quartz capillary tube at around 1200 K. The result is a small flow of S atoms, that can be used also for doping!
Hope this helps, Dirk
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