23 research outputs found
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Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers
The cleaning of two-dimensional (2D) materials is an essential step in the fabrication of future devices, leveraging their unique physical, optical, and chemical properties. Part of these emerging 2D materials are transition metal dichalcogenides (TMDs). So far there is limited understanding of the cleaning of “monolayer” TMD materials. In this study, we report on the use of downstream H2 plasma to clean the surface of monolayer WS2 grown by MOCVD. We demonstrate that high-temperature processing is essential, allowing to maximize the removal rate of polymers and to mitigate damage caused to the WS2 in the form of sulfur vacancies. We show that low temperature in situ carbonyl sulfide (OCS) soak is an efficient way to resulfurize the material, besides high-temperature H2S annealing. The cleaning processes and mechanisms elucidated in this work are tested on back-gated field-effect transistors, confirming that transport properties of WS2 devices can be maintained by the combination of H2 plasma cleaning and OCS restoration. The low-damage plasma cleaning based on H2 and OCS is very reproducible, fast (completed in a few minutes) and uses a 300 mm industrial plasma etch system qualified for standard semiconductor pilot production. This process is, therefore, expected to enable the industrial scale-up of 2D-based devices, co-integrated with silicon technology
Experimental study of the magnetic phase diagram and the vortex dynamics in epitaxial thin films of the Bi2Sr2CaCu2O8 + x High Tc superconductors
Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe
Investigation of the low field irreversibility line in Bi2Sr2CaCu2O8+x epitaxial thin films
SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Ru/Ta bilayer approach to EUV mask absorbers: Experimental patterning and simulated imaging perspective
The optical properties and geometry of EUV mask absorbers play an essential role in determining the imaging performance of a mask in EUV lithography. Imaging metrics, including Normalized Image Log Slope (NILS), Telecentricity Error (TCE), and Best Focus Variation (BFV) through pitch deteriorate because of Mask 3-Dimensional (M3D) effects in EUV lithography, which limits the production efficiency. Alternative absorbers, including alloys of Ru and Ta, are anticipated to reduce some of the M3D effects; however, patterning these materials is challenging due to their low etch rates and poor etch selectivity against the Ru mask capping layer. Therefore, we propose a Ru/Ta bilayer approach to EUV mask absorbers and investigate it from a patterning and imaging standpoint. The top Ru layer thickness is calculated using the thin film interference phenomena, and we determine the bottom Ta layer that can produce improved NILS by utilizing the total absorber thickness optimization methodology. We demonstrate the patterning of the Ru/Ta bilayer using a two-step etch; the top Ru layer is patterned with Cl2-O2 Reactive Ion Etch (RIE), and the bottom Ta layer with Cl2-N2 RIE. The geometry and morphology of the patterned bilayer stack are investigated using TEM (Transmission Electron Microscopy), and interdiffusion at the interface of Ru and Ta is studied using EDS-STEM (Energy Dispersive X-ray Spectroscopy-Scanning Transmission Electron Microscopy). The non-ideal traits of the Ru/Ta bilayer stack, determined by experimental characterization techniques, are used to simulate the imaging performance and then compared against an ideal Ru/Ta bilayer stack, along with the reference Ta-based absorber. Even when non-idealities are considered, the simulation findings demonstrate that the Ru/Ta bilayer absorber exhibits improved NILS and reduced BFV compared to the Ta-based absorber. The outcomes encourage further research into the possibilities of multilayer absorbers, to tailor their optical characteristics by varying the thickness of individual layers
Contact poisons in the ant genus Crematogaster: chemical diversity and biological functions
info:eu-repo/semantics/nonPublishe
Current Aspects in Medicine of the Locomotor System. Urticarial Vasculitis: Apropos of a Case
peer reviewe
Influences of thermal annealing and humidity exposure on surface structure of (100) single-crystal MgO substrate
We studied the influence of thermal annealing on the surface structure of (100) single-crystal MgO substrates by atomic force microscopy (AFM). By annealing MgO substrates at various temperatures for 4 h in flowing oxygen, we showed that the surface reconstruction could be explained by considering surface diffusion, surface evaporation, and condensation. At an annealing temperature of 1473 K, a stepped structure was formed with screw dislocations acting as step sources. The influence of humidity on the surface morphology of MgO substrates was also studied by exposing them to a constant humidity of 40 and 80% for different times. After an exposure time of 1.5 h in 80% humidity, the substrate surface was already covered by reaction products. For the 40% humidity, the corresponding time is 10 h. The major reaction product was identified as Mg(OH)2 by x-ray diffraction.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Structural characterization of epitaxial Bi2Sr2CuO6+δ thin films deposited on SrTiO3 substrates using inverted cylindrical magnetron sputtering
High quality c-axis oriented epitaxial Bi2Sr2CuO6+δ thin films were deposited on 0° and 6° vicinal SrTiO3 (100) substrates using an inverted cylindrical magnetron sputtering method. Their structural properties, regarding the orientation, epitaxy, surface morphology, composition, and surface microstructure, were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The influences of the deposition parameters and substrate surface structure on the structural properties of these epitaxial Bi2Sr2CuO6+δ thin films are studied. A metal-insulator transition is observed with a variation of the Sr deficiency. It is demonstrated that films on 0° and 6° vicinal substrates grow in the two-dimensional and step-flow modes, respectively. Optimal deposition conditions were obtained leading to an extremely smooth film surface and high epitaxial quality.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Low angle deviation from the anisotropic effective mass model in epitaxial YBa2(Cu1-xZnx)3O7-δ thin films
SCOPUS: ar.jinfo:eu-repo/semantics/publishe