The dispersion in chemical abundances provides a very strong constraint on the processes that drive the chemical enrichment of galaxies. Due to its proximity, the spiral galaxy M33 has been the focus ...of numerous chemical abundance surveys to study the chemical enrichment and dispersion in abundances over large spatial scales. The CHemical Abundances Of Spirals (CHAOS) project has observed \(\sim\)100 H II regions in M33 with the Large Binocular Telescope (LBT), producing the largest homogeneous sample of electron temperatures (T\(_e\)) and direct abundances in this galaxy. Our LBT observations produce a robust oxygen abundance gradient of \(-\)0.037 \(\pm\) 0.007 dex/kpc and indicate a relatively small (0.043 \(\pm\) 0.015 dex) intrinsic dispersion in oxygen abundance relative to this gradient. The dispersions in N/H and N/O are similarly small and the abundances of Ne, S, Cl, and Ar relative to O are consistent with the solar ratio as expected for \(\alpha\)-process or \(\alpha\)-process-dependent elements. Taken together, the ISM in M33 is chemically well-mixed and homogeneously enriched from inside-out with no evidence of significant abundance variations at a given radius in the galaxy. Our results are compared to those of the numerous studies in the literature, and we discuss possible contaminating sources that can inflate abundance dispersion measurements. Importantly, if abundances are derived from a single T\(_e\) measurement and T\(_e\)-T\(_e\) relationships are relied on for inferring the temperature in the unmeasured ionization zone, this can lead to systematic biases which increase the measured dispersion up to 0.11 dex.
Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum ...disulfide (MoS2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS2 2D films grown from TiN electrodes across opposite sides have been connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS2 has been shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photo-response measurements on the device structures demonstrate that the electrodeposited MoS2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way towards room temperature, scalable and site-selective production of various transition metal dichalcogenides and their lateral heterostructures for 2D materials-based fabricated devices.
Heterostructures involving two-dimensional (2D) transition metal dichalcogenides and other materials such as graphene have a strong potential to be the fundamental building block of many electronic ...and opto-electronic applications. The integration and scalable fabrication of such heterostructures is of essence in unleashing the potential of these materials in new technologies. For the first time, we demonstrate the growth of few-layer MoS2 films on graphene via non-aqueous electrodeposition. Through methods such as scanning and transmission electron microscopy, atomic force microscopy, Raman spectroscopy, energy and wavelength dispersive X-ray spectroscopies and X-ray photoelectron spectroscopy, we show that this deposition method can produce large-area MoS2 films with high quality and uniformity over graphene. We reveal the potential of these heterostructures by measuring the photo-induced current through the film. These results pave the way towards developing the electrodeposition method for the large-scale growth of heterostructures consisting of varying 2D materials for many applications.
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