46 research outputs found
Towards Ge-based electronic devices: Increased longevity of alkanethiol-passivated Ge(100) in low humidity environments
Get PDFGermanium is a critically important material for future complementary metal-oxide-semiconductor devices, however, to maximise its potential it is necessary to develop a robust passivation process that prevents Ge re-oxidation for a queue time of 24 h. Self-assembled monolayers (SAMs) of alkanethiols on Ge have previously been shown to inhibit oxidation; however, re-oxidation eventually occurs when exposed to ambient conditions. Herein, it is shown that humidity plays a key role in the degradation of the SAM, ultimately resulting in re-oxidation. To demonstrate this, thiol-passivated Ge(100) surfaces are exposed to controlled humidity environments with different levels of relative humidity (RH). The rate of re-oxidation of the Ge surfaces are tracked using X-ray photoelectron spectroscopy and water contact angle analysis to discern what role RH plays in the re-oxidation of the Ge and the degradation of the SAM passivation. Atomic force microscopy data is presented to show that humidity-mediated re-oxidation of the Ge has little or no impact on the route mean square roughness of those surfaces. Finally, atomistic modelling of thiol-SAM passivated Ge in the presence of water molecules has been studied using first principles density functional theory in order to simulate experimental conditions and to understand the atomic level processes that determine stability in hydrophilic and hydrophobic configurations
Fabricating Germanium Interfaces for Battery Applications
No full textThe experimental results presented herein detail the importance of material surfaces in device performance. We have demonstrated this importance by furthering and applying our understanding of germanium surfaces to a number of real-world applications. Pure and stable dispersions of germanane, an “all-surface” form of germanium, were created through solid-state synthesis followed by ultrasonication and centrifugation. These dispersions were used to fabricate germanane-based, high-performance, Li-ion anodes with capacities of ~1100 mA-h/g, capacity retention over 100 cycles, and Coulombic efficiency of 99%. Additionally, carborane monolayers were self-assembled on Ge(100) and Ge(111) surfaces through carboxylic acid tethers, and found to be capable of tuning the surface work function by ~0.4 eV without significantly affecting surface wettability. These capabilities are important for increasing device efficiency while minimizing complications associated with processing. Lastly, we introduce the concept of the molecular battery, a possible design using a layer-by-layer deposition approach, and our steps toward its realization. In this pursuit, we explored the assembly of metal-organic coordination of carborane-based linkers, as well as the capabilities of a film of benzene-based linkers (<50 nm) as a Li-ion battery separator using a Ge anode as a tool for analyzing performance
Work Function Control of Germanium through Carborane-Carboxylic Acid Surface Passivation.
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