Formation Mechanism of Strontium and Titanium Oxide Films by Metalorganic Chemical Vapor Deposition: An Isotopic Labeling Study Using 18O2

Isotopic labeling experiments using 18O2 were carried out to understand the decomposition and oxidation reactions of source molecules in the metalorganic chemical vapor deposition (MOCVD) of strontium and titanium oxide films. The isotopic ratios of oxygen incorporated in the deposited films were determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) in both positive and negative secondary ion detection modes. The obtained M18O+/M16O+ (M=Sr, Ti) ratios showed good agreement with the corresponding 18O-/16O- ratios. The oxygen incorporation from the oxidant gas (18O2) to the strontium oxide films is dominant under typical deposition conditions, while the majority of oxygen in the titanium oxide films originates from the ligands of the source molecules.