The stream of precursor is stopped

The stream of precursor is stopped when the reaction between the precursor and the substrate completes. The residuals of the precursor vapor and byproducts are purged with an inert gas or evacuated at high vacuum. These two steps are called thefrst half-reaction. After thefrst half-reaction, one ALD cycle isnished. If multiple ALD cycles are needed, a second stream of precursor is pulsed into the chamber to regenerate the ligands or functional groups on support surface. After purging to remove the residuals and byproducts, it is ready for next ALD cycle (the second half- reaction in Fig. 2).