Near Room-Temperature Atomic Layer Deposition of Magnesium Oxide Using Bis-3-(N,N-dimethylamino)propyl Magnesium(II) and Water

Magnesium(II) oxide (MgO) is a versatile material that is appealing for a wide range of applications including electronics and biocompatible coatings, as pharmaceutics, and gas barrier layers (GBLs). The growth of MgO films at low temperatures is required for these applications which can be enabled by atomic layer deposition (ALD). However, the chemistry of ALD precursors reported to date for MgO is limited and there are no suitable chemistries for low temperature deposition on sensitive substrates. In this work, we describe the ALD of MgO thin films close to room temperature which was triggered by the use of a new nonpyrophoric Mg precursor that possesses all the prerequisites needed for low temperature ALD. The highly volatile bis-3-(N,N-dimethylamino)propyl magnesium(II) [Mg(DMP)₂] precursor is reactive toward water. The unique chemistry of the DMP ligand facilitates the ALD process in a broad temperature range (30-260 °C) with high growth per cycle (GPC) values (2.40 Å at 40 °C and 1.91 Å at 120 °C) on Si substrates and is supported by computational studies. The as deposited films were characterized using complementary tools to investigate the composition, structure and surface topology. Furthermore, we demonstrate the growth of MgO on poly(ethylene terephthalate) (PET) foils that can be exploited for implementation in temperature sensitive flexible devices by low temperature ALD. This work highlights the key role of the DMP ligand in developing a new Mg precursor promoting low temperature ALD of MgO thin films, opening the field of flexible electronics and new applications beyond semiconductor devices.