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1. Atomic Layer Deposition of Nickel Using Ni(dmamb)2 and ZnO Adhesion Layer Without Plasma

   https://doi.org/10.1007/s41871-024-00238-5  

   Baker, Kaiya; Brown, Hayden; Gebre, Fisseha; Xu, Jiajun (September 2024, Nanomanufacturing and Metrology)

   Abstract In this study, a novel deposition technique that utilizes diethylzinc (C₄H₁₀ZnO) with H₂O to form a ZnO adhesion layer was proposed. This technique was followed by the deposition of vaporized nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)₂) and H₂gas to facilitate the deposit of uniform layers of nickel on the ZnO adhesion layer using atomic layer deposition. Deposition temperatures ranged from 220 to 300 °C. Thickness, composition, and crystallographic structure results were analyzed using spectroscopic ellipsometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. An average growth rate of approximately 0.0105 angstroms per cycle at 260 °C was observed via ellipsometry. Uniform deposition of ZnO with less than 1% of Ni was displayed by utilizing the elemental analysis function via SEM, thereby providing high-quality images. XPS revealed ionizations consistent with nickel and ZnO through the kinetic and binding energies of each detected electron. XRD provided supplemental information regarding the validity of ZnO by exhibiting crystalline attributes, revealing the presence of its hexagonal wurtzite structure. 

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2. Unusual layer-by-layer growth of epitaxial oxide islands during Cu oxidation

   https://doi.org/10.1038/s41467-021-23043-w  

   Li, Meng; Curnan, Matthew T.; Gresh-Sill, Michael A.; House, Stephen D.; Saidi, Wissam A.; Yang, Judith C. (May 2021, Nature Communications)

   Abstract Elucidating metal oxide growth mechanisms is essential for precisely designing and fabricating nanostructured oxides with broad applications in energy and electronics. However, current epitaxial oxide growth methods are based on macroscopic empirical knowledge, lacking fundamental guidance at the nanoscale. Using correlated in situ environmental transmission electron microscopy, statistically-validated quantitative analysis, and density functional theory calculations, we show epitaxial Cu₂O nano-island growth on Cu is layer-by-layer along Cu₂O(110) planes, regardless of substrate orientation, contradicting classical models that predict multi-layer growth parallel to substrate surfaces. Growth kinetics show cubic relationships with time, indicating individual oxide monolayers follow Frank-van der Merwe growth whereas oxide islands follow Stranski-Krastanov growth. Cu sources for island growth transition from step edges to bulk substrates during oxidation, contrasting with classical corrosion theories which assume subsurface sources predominate. Our results resolve alternative epitaxial island growth mechanisms, improving the understanding of oxidation dynamics critical for advanced manufacturing at the nanoscale. 

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3. Cortical layer–specific critical dynamics triggering perception

   https://doi.org/10.1126/science.aaw5202  

   Marshel, James H.; Kim, Yoon Seok; Machado, Timothy A.; Quirin, Sean; Benson, Brandon; Kadmon, Jonathan; Raja, Cephra; Chibukhchyan, Adelaida; Ramakrishnan, Charu; Inoue, Masatoshi; et al (August 2019, Science)

   Perceptual experiences may arise from neuronal activity patterns in mammalian neocortex. We probed mouse neocortex during visual discrimination using a red-shifted channelrhodopsin (ChRmine, discovered through structure-guided genome mining) alongside multiplexed multiphoton-holography (MultiSLM), achieving control of individually specified neurons spanning large cortical volumes with millisecond precision. Stimulating a critical number of stimulus-orientation-selective neurons drove widespread recruitment of functionally related neurons, a process enhanced by (but not requiring) orientation-discrimination task learning. Optogenetic targeting of orientation-selective ensembles elicited correct behavioral discrimination. Cortical layer–specific dynamics were apparent, as emergent neuronal activity asymmetrically propagated from layer 2/3 to layer 5, and smaller layer 5 ensembles were as effective as larger layer 2/3 ensembles in eliciting orientation discrimination behavior. Population dynamics emerging after optogenetic stimulation both correctly predicted behavior and resembled natural internal representations of visual stimuli at cellular resolution over volumes of cortex. 

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4. Complementary networks of cortical somatostatin interneurons enforce layer specific control

   https://doi.org/10.7554/eLife.43696  

   Naka, Alexander; Veit, Julia; Shababo, Ben; Chance, Rebecca K; Risso, Davide; Stafford, David; Snyder, Benjamin; Egladyous, Andrew; Chu, Desiree; Sridharan, Savitha; et al (March 2019, eLife)

   The neocortex is functionally organized into layers. Layer four receives the densest bottom up sensory inputs, while layers 2/3 and 5 receive top down inputs that may convey predictive information. A subset of cortical somatostatin (SST) neurons, the Martinotti cells, gate top down input by inhibiting the apical dendrites of pyramidal cells in layers 2/3 and 5, but it is unknown whether an analogous inhibitory mechanism controls activity in layer 4. Using high precision circuit mapping, in vivo optogenetic perturbations, and single cell transcriptional profiling, we reveal complementary circuits in the mouse barrel cortex involving genetically distinct SST subtypes that specifically and reciprocally interconnect with excitatory cells in different layers: Martinotti cells connect with layers 2/3 and 5, whereas non-Martinotti cells connect with layer 4. By enforcing layer-specific inhibition, these parallel SST subnetworks could independently regulate the balance between bottom up and top down input. 

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5. Controlled layer-by-layer assembly and structured coloration of Ti3C2Tz MXene/polyelectrolyte heterostructures

   https://doi.org/10.1038/s41699-024-00514-4  

   Neal, Natalie_N; Arole, Kailash; Cao, Huaixuan; Kotasthane, Vrushali; Xiang, Sisi; Ross, Diego; Stevenson, Peter_R; Radovic, Miladin; Green, Micah_J; Lutkenhaus, Jodie_L (November 2024, npj 2D Materials and Applications)

   Abstract Structural color arises from light scattering rather than organic pigments and can be found in Nature, such as in bird feathers and butterfly wings. Synthetic materials can mimic Nature by leveraging materials with contrasting optical characteristics by controlling each materials’ spatial arrangement in a heterostructure. Two-dimensional MXene nanosheets are particularly interesting due to their unique optical properties, but MXenes have not been used directly as a structural colorant because it is challenging to control the spatial placement of MXenes at the nanometer level. Here, we report the emergence of structural color in layer-by-layer (LbL) assemblies of Ti₃C₂T_zMXene nanosheets and polyelectrolyte heterostructures with controlled block thicknesses. The block thickness and spatial placement of MXene are controlled by the assembly’s salt concentration and number of layer pairs. This work demonstrates that optical characteristics of MXene/polyelectrolyte heterostructures depend on MXene content and placement, while deepening the understanding of MXenes within structural color films. 

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