We conclude that the surface changes its termination reversibly during each ALD cycle. When exposed to TDMAH, the surface gradually becomes amine -NMe2 terminated due to the formation of TDMAH-derived surface species (appearance of signals). When exposed to D2S, surface-bound -NMe2 species are converted into volatile DNMe2 species (loss of signals) and a thiol (-SD) termination forms. The thiol-terminated surface can react with TDMAH again, enabling the next ALD cycle.