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In view of its epitaxial seeding capability, c-plane single crystalline sapphire represents one of the most enticing, industry-compatible templates to realize manufacturable deposition of single crystalline two-dimensional transition metal dichalcogenides (MX2) for functional, ultrascaled, nanoelectronic devices beyond silicon. Despite sapphire being atomically flat, the surface topography, structure, and chemical termination vary between sapphire terraces during the fabrication process. To date, it remains poorly understood how these sapphire surface anomalies affect the local epitaxial registry and the intrinsic electrical properties of the deposited MX2 monolayer. Therefore, molybdenum disulfide (MoS2) is deposited by metal-organic chemical vapor deposition (MOCVD) in an industry-standard epitaxial reactor on two types of c-plane sapphire with distinctly different terrace and step dimensions. Complementary scanning probe microscopy techniques reveal an inhomogeneous conductivity profile in the first epitaxial MoS2 monolayer on both sapphire templates. MoS2 regions with poor conductivity correspond to sapphire terraces with uncontrolled topography and surface structure. By intentionally applying a substantial off-axis cut angle (1° in this work), the sapphire terrace width and step height-and thus also surface structure-become more uniform across the substrate and MoS2 conducts the current more homogeneously. Moreover, these effects propagate into the extrinsic MoS2 device performance: the field-effect transistor variability reduces both within and across wafers at higher median electron mobility. Carefully controlling the sapphire surface topography and structure proves an essential prerequisite to systematically study and control the MX2 growth behavior and capture the influence on its structural and electrical properties.

An Intelligent and self-adaptive constellation iterative algorithm for enhanced probabilistically shaped hexagonal CAP-19 modulation is proposed in this paper. Experimental results indicate the superiority of the proposed modulation scheme for rate-adaptive optical transmissions. © 2020 The Author(s)

Acute temperature stress in 15-day post-hatch (DPH) Lates calcarifer larvae was studied using the semi-static bioassay method to understand the physical response of fish larvae to low temperature. In this study, 20oC, 22oC, 24oC, and 26oC were tested and 28oC was the control. Antioxidant enzyme activity including superoxide dismutase (SOD), peroxidase (POD), catalase, acid phosphatase (ACP), glutathione peroxidase (GSH-Px) and digestive enzymes including lipase, amylase, trypsin, pepsin were used as the physical indicators. SOD activities were elevated to scavenge excess reactive oxygen species (ROS) after exposure to lower temperatures, and their activities increased dramatically in relation to the increasing residue time. POD enzyme activity maintained a low level in the early stage of cold exposure and increased to a high level in relation to exposure time. Catalase, GSH-Px, and ACP activities were elevated in fish after exposure to lower temperatures compared to those in fish maintained at 28oC. Lipase activity decreased after exposure to lower temperatures and modestly elevated over time. The highest amylase activity was observed in the control group. However, trypsin and pepsin activity was elevated with the decrease of environmental temperature. Our results indicate that lower temperature significantly affects activity of antioxidant enzymes and digestive enzymes in barramundi larvae. Barramundi larvae exhibited a certain tolerance of low temperature for a short period. Results from the present study will improve our understanding of the physical response of warm water fish to low temperatures and can therefore guide hatchery practices for Lates calcarifer.