The system was differentially pumped and the operating pressure during typical measurements is kept in the order of 10 -6 mbar to enable mean free paths that allow collisionless particle transport of the ions from the orifice to the detector. The Bar Scan measurements covered a mass range of 1 to 50 atomic mass units (amu), which was suitable for detecting all relevant masses while maintaining a high scanning speed. To analyze the formation of reaction products and the utilization of reactant species, a series of MID measurements were carried out. The MID-scan involved five complete ALD cycles (both precursor and reactant pulses).