Despite the synthesis method employed, PtSi forms in the same way. When pure platinum is first heated with silicon,  is formed. Once all the available Pt and Si are used and the only available surfaces are , the silicide will begin the slower reaction of converting into PtSi. The activation energy for the  reaction is around 1.38 eV, while it is 1.67 eV for PtSi. 
Oxygen is extremely detrimental to the reaction, as it will bind preferably to Pt, limiting the sites available for Pt–Si bonding and preventing the silicide formation. A partial pressure of  as low at 10 has been found to be sufficient to slow the formation of the silicide. To avoid this issue inert ambients are used, as well as small annealing chambers to minimize amount of potential contamination. The cleanliness of the metal film is also extremely important, and unclean conditions result in poor PtSi synthesis. 
In certain cases an oxide layer can be beneficial. When PtSi is used as a Schottky barrier, an oxide layer prevents wear of the PtSi.