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Atomic Layer Deposition of h-BN(0001) for Passivation on Germanium and Lithium Garnet Substrates and Oxygen Radical Surface InteractionsOmolere, Olatomide Bamidele 05 1900 (has links)
Boron nitride (BN) protective coatings have found extensive use in electrochemical batteries. Atomic layer deposition (ALD) was employed to deposit a thin BN layer onto solid Li-garnet electrolytes, utilizing a halide-free precursor, tris(dimethylamino)borane, and NH3 at 723 K. This process resulted in a 3 nm BN cap that effectively prevented Li2CO3 formation, a detrimental compound within Li-based electrolytes. The BN-coated Li-garnets exhibited remarkable stability under ambient conditions, confirmed through X-ray photoelectron spectroscopy (XPS) analysis, lasting for over 2 months. Moreover, the BN coating played a crucial role in stabilizing the Li anode/electrolyte interface, significantly reducing interfacial resistance to 18 Ω·cm². This enhancement increased critical current density and demonstrated impressive capacitance retention, exceeding 98% over 100 cycles. This research highlights the essential role of ALD in ensuring uniform BN growth. This precision is vital for suppressing Li dendrite growth, which has the potential to extend battery lifespan and enhance overall performance. The examination of oxygen radicals' interactions with surfaces holds crucial technological significance across diverse applications, including surface modification, microelectronics processing, thin film deposition, and space technologies. Ab initio molecular dynamics (AIMD) simulations are a potent tool for exploring bond-breaking pathways initiated by O radicals. These simulations provide detailed insights into how these pathways evolve concerning radical kinetic energy and trajectory. They effectively scrutinize reactions induced by oxygen radicals with varying kinetic energies, whether they are in their ground state (O 3P) or excited state (O 1D). Moreover, this discussion introduces novel calculations that reveal the potential for similar reaction products by adjusting kinetic energy in ground state oxygen or reducing kinetic energy in excited state oxygen. This energy modulation helps overcome activation barriers governing specific bond-breaking events within model systems. Germanium (Ge) is emerging as a potential Si replacement in high-performance CMOS technology. However, Ge's native oxide layer is less stable than Si's, limiting its semiconductor applications. Achieving an oxygen-free Ge surface is challenging. In-situ XPS revealed atomic oxygen's effectiveness at removing surface hydrocarbons at room temp. Atomic hydrogen at 350°C removes germanium oxide (GeO2). ALD of 3-monolayer h-BN film was deposited using tris (dimethyl amino) borane and NH3 at 450°C using ALD. XPS analysis showed it shields the Ge substrate from room-temp atomic oxygen oxidation, with only the outermost BN layer oxidizing. This is the first report of ALD-deposited h-BN on Ge surfaces. Atomic oxygen from a thermal cracker effectively removes carbon contaminants from a Ge surface exposed to room temperature ambient conditions.
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