Solvent vapor annealing of block copolymer thin films can produce a range of morphologies different from the equilibrium bulk morphology. By systematically varying the flow rate of two different solvent vapors (toluene and n-heptane) and an inert gas, phase maps showing the morphology versus vapor pressure of the solvents were constructed for 45 kg/mol polystyrene-block-polydimethylsiloxane diblock copolymer films of different thicknesses. The final morphology was correlated with the swelling of the block copolymer and homopolymer films and the solvent vapor annealing conditions. Self-consistent field theory is used to model the effects of solvent swelling. These results provide a framework for predicting the range of morphologies available under different solvent vapor conditions, which is important in lithographic applications where precise control of morphology and critical dimensions are essential.

Recent advances in the field of two-dimensional (2D) transition metal dichalcogenide (TMD) materials have indicated that atomic layer deposition (ALD) of the metal oxide and subsequent sulfidation could offer a method for the synthesis of large area two-dimensional materials such as MoS2 with excellent layer control over the entire substrate. However, growing large area oxide films by ALD with sub 1 nm nucleation coalescence remains a significant challenge, and the necessary steps are unexplored. In this work, we demonstrate the necessary process improvements required to achieve sub 1 nm nucleation control by characterization of nucleation domains formed by oxide deposition. Synthesis of the TMD MoS2 from sulfidation of oxide deposited by both thermal ALD from (tBuN)2(NMe2)2Mo and O3 and plasma enhanced ALD (PEALD) from (tBuN)2(NMe2)2Mo and remote O2 plasma was performed. Large uniform MoS2 areas were achieved by optimizing the effects of various growth process conditions and surface treatments on the ALD nucleation and growth of Mo-oxide and the postsulfidation of MoS2. In addition to insights into the control of the oxide deposition, film chemistry analysis during a multistep sulfidation based on less toxic sulfur as compared to H2S was performed for several temperature profiles revealing sulfur incorporation and molybdenum reduction at low temperatures but higher temperatures required for 2H crystal structure formation. The knowledge gained of the ALD, PEALD, and postsulfidation was leveraged to demonstrate tunable film thickness and centimeter-scale monolayer growth. Material quality can be studied independently of the MoS2 layer count as demonstrated by the control of the monolayer photoluminescence intensity by the temperature ramp rate during sulfidation.

Disordered carbon materials, both amorphous and with long-range order, have been used in a variety of applications, from conductive additives and contact materials to transistors and photovoltaics. Here we show a flexible solution-based method of preparing thin films with tunable electrical properties from suspensions of ball-milled coals following centrifugation. The as-prepared films retain the rich carbon chemistry of the starting coals with conductivities ranging over orders of magnitude, and thermal treatment of the resulting films further tunes the electrical conductivity in excess of 7 orders of magnitude. Optical absorption measurements demonstrate tunable optical gaps from 0 to 1.8 eV. Through low-temperature conductivity measurements and Raman spectroscopy, we demonstrate that variable range hopping controls the electrical properties in as-prepared and thermally treated films and that annealing increases the sp 2 content, localization length, and disorder. The measured hopping energies demonstrate electronic properties similar to amorphous carbon materials and reduced graphene oxide. Finally, Joule heating devices were fabricated from coal-based films, and temperatures as high as 285°C with excellent stability were achieved. KEYWORDS: Coal, amorphous carbon, organic semiconductors, thin films, solution processing C arbon has long been known as one of the most chemically versatile elements. As a result, carbonaceous materials have been of technological interest for their wide range of electronic propertiesresulting in materials ranging from low cost conducting materials such as graphite and carbon black, to semiconducting fullerenes and carbon nanotubes, and to insulating diamond and diamond-like carbon. Specifically, carbon black, carbon filaments, and other carbon materials are used in electrodes, conductivity additives, and electromagnetic reflectors. 1 Graphitic materials 2 and amorphous carbon (a-C) 3,4 are the leading and a promising candidate, respectively, for anode materials in lithium ion batteries. Amorphous carbon has also been used in the manufacturing of transistors 5,6 and photovoltaic devices, 7,8 and nanostructured graphitic materials (such as graphene and reduced graphene oxide) have gained significant attention for applications including in photovoltaics, 9−11 transparent conductive membranes, 12−16 and Joule heating devices. 17−19 Despite decades of research on synthetically processed carbon materials, facile, tunable, 20 low-temperature, solution processing methods remain elusive. Carbon black synthesis requires temperatures as high as 2000°C, 21 and a-C is typically deposited by plasma-enhanced chemical vapor deposition (CVD) 22,23 although aerosol-assisted CVD has recently been demonstrated. 8 While extensive research has been conducted to develop solution-based methods of graphene deposition, rGO films remain several orders of magnitude less conductive than CVD graphene. 16,24,25 In contrast to the widely studied world of synthetic carbonaceous materials, the optical...

Natural carbons, such as coal and petroleum feedstocks, or the undesirable by-products of subsequent chemical processing of these feedstocks, such as tars, comprise a huge chemical phase space incorporating a wide range of chemical, optical, and

Plasma enhanced atomic layer deposition of Al2O3 gate dielectric thin films on AlGaN/GaN substrates: The role of surface predeposition treatments

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