Atomic Layer Deposition of MgO Using Bis(ethylcyclopentadienyl)magnesium and H₂O

Magnesium oxide (MgO) atomic layer deposition (ALD) was performed using sequential exposures of bis(ethylcyclopentadienyl)magnesium (Mg(CpEt) 2 ) and H 2 O. Quartz crystal microbalance (QCM) measurements monitored the mass deposition during MgO ALD and verified self-limiting reactions for each reactant. Extremely efficient reactions were observed that required reactant exposures of only ∼1 × 10 4 L (1 L = 1 × 10 −6 Torr s). X-ray reflectivity (XRR) studies were used to confirm the QCM measurements and determine the film density and film thicknesses. The MgO ALD film density was 3.07 g/cm 3 . The largest MgO ALD growth per cycle was 1.42 Å/cycle at 150 °C and the growth per cycle decreased for temperatures >150 °C. Fourier transform infrared spectroscopy was used to study the CpEt* and OH* surface species during MgO ALD and also to monitor the bulk vibrational modes of the growing MgO films. Transmission electron microscopy of MgO ALD on ZrO 2 nanoparticles revealed the conformality of the MgO films and confirmed the growth per cycle observed by the XRR studies. X-ray diffraction determined that the MgO ALD films were crystalline and consistent with the cubic phase. Rutherford backscattering determined that the Mg:O stoichiometry of the MgO ALD films was 0.95:1.05. The results allowed a growth mechanism to be established for MgO ALD using Mg(CpEt) 2 and H 2 O. Only 30.8% of the Mg sites are observed to retain the CpEt* surface species after the Mg(CpEt) 2 exposure. The efficient ALD of MgO using Mg(CpEt) 2 and H 2 O should be useful for a variety of applications including the conformal coating of particles.