Without the extra gas pulse, the desorbed surface methyl groups could re-adsorb before the NH3 is introduced into the chamber which could lead to them being trapped in the film. Carbon impurities in semiconductor grade materials is a problem, typically, when deposited at high temperature and we believe that this ABC-type pulsed process (were A is TMA pulse, B is the extra pulse and C is NH3 pulse) could possibly be a solution to accomplish high temperature ALD films with low C impurities.