A Liquid Ge(IV) Precursor for Low Temperature Plasma Enhanced Atomic Layer Deposition of Germanium Oxide Thin Films

ABSTRACT Germanium oxide thin films are promising for advanced applications such as microelectronics, optoelectronics, high‐power electronics, optics, and biomedical uses. However, scalable and controlled low‐temperature synthesis of GeO ₂ thin films via atomic layer deposition (ALD) is limited by the small range of available Ge precursors. We introduce monomeric tetrakis‐3‐( N , N ‐dimethylamino)propyl germanium(IV) [Ge(DMP) ₄ ] as a promising Ge precursor. It is non‐pyrophoric, thermally stable, and liquid, and can be obtained in high purity on a multigram scale through an industrially feasible synthesis. Using density functional theory (DFT) and mass spectrometry (MS), we rationalize the coordination environment and identify a feasible chemisorption pathway, indicating a high reactivity of the precursor. Subsequently, [Ge(DMP) ₄ ] was employed in low‐temperature plasma‐enhanced ALD (PEALD) over a wide temperature range from 40°C to 240°C, yielding smooth, uniform germanium oxide films. Rapid and homogeneous nucleation leads to dense films with sub‐nanometer thickness. By adjusting the deposition temperature and plasma duration, the film composition could be readily tuned from GeO ₂ to sub‐stoichiometric GeO _x . These findings establish [Ge(DMP) ₄ ] as an effective, scalable precursor for low‐temperature ALD of GeO ₂ , emphasizing the critical role of precursor chemistry in ALD process development.