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1. Atomic and Molecular Layer Deposition of Hybrid Mo–Thiolate Thin Films with Enhanced Catalytic Activity

   https://doi.org/10.1002/adfm.201800852  

   MacIsaac, Callisto ; Schneider, Joel R. ; Closser, Richard G. ; Hellstern, Thomas R. ; Bergsman, David S. ; Park, Joonsuk ; Liu, Yunzhi ; Sinclair, Robert ; Bent, Stacey F. ( April 2018 , Advanced Functional Materials)

   A synthetic route toward hybrid MoS₂‐based materials that combines the 2D bonding of MoS₂with 3D networking of aliphatic carbon chains is devised, leading to a film with enhanced electrocatalytic activity. The hybrid inorganic–organic thin films are synthesized by combining atomic layer deposition (ALD) with molecular layer deposition (MLD) using the precursors molybdenum hexacarbonyl and 1,2‐ethanedithiol and characterized by in situ Fourier transform infrared spectroscopy, and the resultant material properties are probed by X‐ray photoelectron spectroscopy, Raman spectroscopy, and grazing incidence X‐ray diffraction. The process exhibits a growth rate of 1.3 Å per cycle, with an ALD/MLD temperature window of 155–175 °C. The hybrid films are moderately stable for about a week in ambient conditions, smooth (σ_RMS≈ 5 Å for films 60 Å thick) and uniform, with densities ranging from 2.2–2.5 g cm⁻³. The material is both optically transparent and catalytically active for the hydrogen evolution reaction (HER), with an overpotential (294 mV at −10 mA cm⁻²) superior to that of planar MoS₂. The enhancement in catalytic activity is attributed to the incorporation of organic chains into MoS₂, which induces a morphological change during electrochemical testing that increases surface area and yields high activity HER catalysts without the need for deliberate nanostructuring.

    

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2. Low‐Temperature Dual‐Material Area‐Selective Deposition: Molybdenum Hexafluoride‐Mediated SiO 2 Fluorination/Passivation for Self‐Aligned Molybdenum/Metal Oxide Nanoribbons

   https://doi.org/10.1002/adfm.202316872  

   Oh, Hwan ; Thelven, Jeremy M. ; Margavio, Hannah R. M. ; Parsons, Gregory N. ( April 2024 , Advanced Functional Materials)

   Area‐selective deposition (ASD) is a forefront nanopatterning technique gaining substantial attention in the semiconductor industry. While current research primarily addresses single‐material ASD, exploring multi‐material ASD is essential for mitigating complexity in advanced nanopatterning. This study describes molybdenum hexafluoride (MoF₆)‐mediated fluorination/passivation of the hydroxylated SiO₂(SiO₂‒OH) at 250 °C as a new method to pacify nucleation during subsequent ZnO and TiO₂atomic layer deposition (ALD). In contrast, Al₂O₃ALD is not passivated on the fluorinated SiO₂(SiO₂‒F). The study further shows that Mo ALD using MoF₆and silane (1 wt% SiH₄in Ar) selectively proceeds on hydrogen‐terminated Si (Si‒H), whereas SiO₂‒OH becomes fluorine‐passivated without observable Mo deposition. This enables subsequent ZnO and TiO₂ASD on Mo versus SiO₂‒F, as confirmed by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). Proposed growth and inhibition mechanisms highlight the importance of the metal oxide precursor in achieving selectivity. Taken together, self‐aligned Mo/ZnO and Mo/TiO₂nanoribbons are demonstrated on coplanar nanoscale Si‒H/SiO₂‒OH patterns by sequentially integrating two individual ASD processes: 1) Mo ASD on Si‒H versus SiO₂‒OH; and 2) ZnO or TiO₂ASD on Mo versus SiO₂‒F. This work highlights the potential for this approach in new ASD systems.

    

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3. Comparison of Hafnium Dioxide and Zirconium Dioxide Grown by Plasma-Enhanced Atomic Layer Deposition for the Application of Electronic Materials

   https://doi.org/10.3390/cryst10020136  

   Xiao, Zhigang ; Kisslinger, Kim ; Chance, Sam ; Banks, Samuel ( February 2020 , Crystals)

   We report the growth of nanoscale hafnium dioxide (HfO2) and zirconium dioxide (ZrO2) thin films using remote plasma-enhanced atomic layer deposition (PE-ALD), and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using the HfO2 and ZrO2 thin films as the gate oxide. Tetrakis (dimethylamino) hafnium (Hf[N(CH3)2]4) and tetrakis (dimethylamino) zirconium (IV) (Zr[N(CH3)2]4) were used as the precursors, while O2 gas was used as the reactive gas. The PE-ALD-grown HfO2 and ZrO2 thin films were analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The XPS measurements show that the ZrO2 film has the atomic concentrations of 34% Zr, 2% C, and 64% O while the HfO2 film has the atomic concentrations of 29% Hf, 11% C, and 60% O. The HRTEM and XRD measurements show both HfO2 and ZrO2 films have polycrystalline structures. n-channel and p-channel metal-oxide semiconductor field-effect transistors (nFETs and pFETs), CMOS inverters, and CMOS ring oscillators were fabricated to test the quality of the HfO2 and ZrO2 thin films as the gate oxide. Current-voltage (IV) curves, transfer characteristics, and oscillation waveforms were measured from the fabricated transistors, inverters, and oscillators, respectively. The experimental results measured from the HfO2 and ZrO2 thin films were compared. 

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4. Synthesis of High Refractive Index Polymer Thin Films for Soft, Flexible Optics Through Halomethane Quaternization of Poly(4‐Vinylpyridine)

   https://doi.org/10.1002/adom.202302201  

   Huo, Ni ; Rivkin, Jeremy ; Jia, Ruobin ; Zhao, Yineng ; Tenhaeff, Wyatt E. ( January 2024 , Advanced Optical Materials)

   Applications in soft, flexible optical, and optoelectronic applications demand polymer thin film coatings that can accommodate substantial physical deformations. The preparation of high refractive index polymers (HRIPs) through the quaternization of poly(4‐vinylpyridine) (P4VP) thin films with (di)halomethanes is presented. P4VP thin films are prepared by initiated chemical vapor deposition (iCVD) and then quaternized through exposure to saturated vapors of iodomethane (CH₃I), dibromomethane (CH₂Br₂), and diiodomethane (CH₂I₂), resulting in refractive indices (RI) as high as 1.67, 1.71, and 2.07, respectively (at 632.8 nm). Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) confirmed the quaternization of pyridine pendant groups on the polymer chain to n‐methylpyridinium with primarily an iodide or bromide counterion, though a minor fraction of polyiodides are also detected. Additionally, these films demonstrate superior thermal stability, retaining their refractive index and thickness after thermal excursions to 200 °C. The halogenated P4VP films exhibit superior mechanical flexibility relative to conventional inorganic coatings (Al₂O₃and Ta₂O₅) and do not fracture at uniaxial tensile strains as high as 10%. This new material chemistry and fabrication approach method may enable advanced optical designs and functionality in a wide range of substrates and device architectures.

    

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5. Facile synthesis of highly fluorescent free-standing films comprising graphitic carbon nitride (g-C 3 N 4 ) nanolayers

   https://doi.org/10.1039/C9NJ05108B  

   Yadav, Ram Manohar ; Kumar, Rajesh ; Aliyan, Amir ; Dobal, Pramod S. ; Biradar, Santoshkumar ; Vajtai, Robert ; Singh, Dinesh Pratap ; Martí, Angel A. ; Ajayan, Pulickel M. ( February 2020 , New Journal of Chemistry)

   Astounding graphitic carbon nitride (g-C 3 N 4 ) nanostructures have attracted huge attention due to their unique electronic structures, suitable band gap, and thermal and chemical stability, and are insinuating as a promising candidate for photocatalytic and energy harvesting applications. The growth of a free-standing film is desirable for widespread electronic devices and electrochemical applications. Here, we present a facile approach to prepare free-standing films (15 mm × 10 mm × 0.5 mm) comprising g-C 3 N 4 nanolayers by the pyrolysis of dicyandiamide (C 2 H 4 N 4 ) utilizing the chemical vapor deposition (CVD) technique. The synthesis is done under low-pressure conditions of argon (∼3 Torr) and at a temperature of 600 °C. The as-synthesized g-C 3 N 4 films are systematically studied for their structural/microstructural characterization using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy techniques. The excitation-dependent photoluminescence (PL) spectra of the as-synthesized g-C 3 N 4 film exhibited an intense, stable and broad emission peak in the visible region at ∼459 nm. The emission spectra of free-standing g-C 3 N 4 films show a blue shift and band sharpening compared to that of the g-C 3 N 4 powder. 

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