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1. Degradation of Perfluorooctanoic Acid on Aluminum Oxide Surfaces: New Mechanisms from Ab Initio Molecular Dynamics Simulations

   https://doi.org/10.1021/acs.est.3c00948  

   Biswas, Sohag ; Wong, Bryan M. ( April 2023 , Environmental Science & Technology)
2. Tailoring the aluminum nanocrystal surface oxide for all-aluminum-based antenna-reactor plasmonic photocatalysts

   https://doi.org/10.1073/pnas.2321852121  

   Bayles, Aaron ; Fabiano, Catherine J. ; Shi, Chuqiao ; Yuan, Lin ; Yuan, Yigao ; Craft, Nolan ; Jacobson, Christian R. ; Dhindsa, Parmeet ; Ogundare, Adebola ; Mendez Camacho, Yelsin ; et al ( March 2024 , Proceedings of the National Academy of Sciences)

   Aluminum nanocrystals (AlNCs) are of increasing interest as sustainable, earth-abundant nanoparticles for visible wavelength plasmonics and as versatile nanoantennas for energy-efficient plasmonic photocatalysis. Here, we show that annealing AlNCs under various gases and thermal conditions induces substantial, systematic changes in their surface oxide, modifying crystalline phase, surface morphology, density, and defect type and concentration. Tailoring the surface oxide properties enables AlNCs to function as all-aluminum-based antenna-reactor plasmonic photocatalysts, with the modified surface oxides providing varying reactivities and selectivities for several chemical reactions.

    

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3. Accessibility and Mechanical Stability of Nanoporous Zinc Oxide and Aluminum Oxide Coatings Synthesized via Infiltration of Polymer Templates

   https://doi.org/10.3390/polym15204088  

   Omotosho, Khalil D. ; Lyon, Zachary ; Shevchenko, Elena V. ; Berman, Diana ( October 2023 , Polymers)

   The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings—polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions.

    

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4. Ferroelectric Tunneling Junctions Based on Aluminum Oxide/ Zirconium-Doped Hafnium Oxide for Neuromorphic Computing

   https://doi.org/10.1038/s41598-019-56816-x  

   Ryu, Hojoon ; Wu, Haonan ; Rao, Fubo ; Zhu, Wenjuan ( December 2019 , Scientific Reports)

   Ferroelectric tunneling junctions (FTJs) with tunable tunneling electroresistance (TER) are promising for many emerging applications, including non-volatile memories and neurosynaptic computing. One of the key challenges in FTJs is the balance between the polarization value and the tunneling current. In order to achieve a sizable on-current, the thickness of the ferroelectric layer needs to be scaled down below 5 nm. However, the polarization in these ultra-thin ferroelectric layers is very small, which leads to a low tunneling electroresistance (TER) ratio. In this paper, we propose and demonstrate a new type of FTJ based on metal/Al₂O₃/Zr-doped HfO₂/Si structure. The interfacial Al₂O₃layer and silicon substrate enable sizable TERs even when the thickness of Zr-doped HfO₂(HZO) is above 10 nm. We found that F-N tunneling dominates at read voltages and that the polarization switching in HZO can alter the effective tunneling barrier height and tune the tunneling resistance. The FTJ synapses based on Al₂O₃/HZO stacks show symmetric potentiation/depression characteristics and widely tunable conductance. We also show that spike-timing-dependent plasticity (STDP) can be harnessed from HZO based FTJs. These novel FTJs will have high potential in non-volatile memories and neural network applications.

    

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5. Improving the Passivation of Molybdenum Oxide Hole‐Selective Contacts with 1 nm Hydrogenated Aluminum Oxide Films for Silicon Solar Cells

   https://doi.org/10.1002/pssa.202000093  

   Gregory, Geoffrey ; Feit, Corbin ; Gao, Zhengning ; Banerjee, Parag ; Jurca, Titel ; Davis, Kristopher O. ( June 2020 , physica status solidi (a))

   The intrinsic and doped amorphous silicon layers in silicon heterojunction solar cells parasitically absorb light in the short wavelength region of the solar spectrum, lowering the generation current available to the device. Herein, a promising alternative to the hole‐selective amorphous silicon contact layers using only wide bandgap, transparent oxide materials is presented. Using thermal atomic layer deposition, a 1 nm hydrogenated aluminum oxide layer is deposited followed by a 4 nm molybdenum oxide layer on n‐type crystalline silicon. This contact stack provides an effective carrier lifetime of 1.14 ms. It is shown that the molybdenum oxide layer is successfully deposited with a high work function, which facilitates efficient hole extraction and repels majority carriers from the c‐Si surface. Then the implied open‐circuit voltage, saturation current density, and contact resistivity are recorded as a function of contact annealing temperature and show that they are relatively stable up to 200 °C.

    

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