It has been established that when silicon is heated above 1300°K in a borosilicate glass vacuum system from 1011to 1015acceptors per cm2are normally added to the silicon surface, even though the glass walls remain at room temperature. The acceptor diffuses into the surface upon heating forming aplayer several microns deep.There is strong evidence that the acceptor is boron from the borosilicate glass envelope. The transfer to the silicon is believed to occur through volatilization of boron oxides by water vapor.