Deploying advanced imaging solutions to robotic and autonomous systems by mimicking human vision requires simultaneous acquisition of multiple fields of views, named the peripheral and fovea regions. Among 3D computer vision techniques, LiDAR is currently considered at the industrial level for robotic vision. Notwithstanding the efforts on LiDAR integration and optimization, commercially available devices have slow frame rate and low resolution, notably limited by the performance of mechanical or solid-state deflection systems. Metasurfaces are versatile optical components that can distribute the optical power in desired regions of space. Here, we report on an advanced LiDAR technology that leverages from ultrafast low FoV deflectors cascaded with large area metasurfaces to achieve large FoV (150°) and high framerate (kHz) which can provide simultaneous peripheral and central imaging zones. The use of our disruptive LiDAR technology with advanced learning algorithms offers perspectives to improve perception and decision-making process of ADAS and robotic systems.
The effect of annealing of Co∕ZnO(0001) was studied by scanning tunneling microscopy, low energy electron diffraction, and Auger electron spectroscopy. At room temperature, Co forms islands on ZnO. Annealing up to 940K leads to coalescence of the islands. At 970K, Co diffuses into ZnO where it partially replaces Zn. A model of the Auger intensities, based on exponential attenuation with thickness and including correction for matrix effects, confirms this interpretation and suggests that the fraction of Zn replaced by Co is near 50% or higher.
SummaryOur aim was to elaborate a novel method for fully controllable large-scale nanopatterning. We investigated the influence of the surface topology, i.e., a pre-pattern of hydrogen silsesquioxane (HSQ) posts, on the self-organization of polystyrene beads (PS) dispersed over a large surface. Depending on the post size and spacing, long-range ordering of self-organized polystyrene beads is observed wherein guide posts were used leading to single crystal structure. Topology assisted self-organization has proved to be one of the solutions to obtain large-scale ordering. Besides post size and spacing, the colloidal concentration and the nature of solvent were found to have a significant effect on the self-organization of the PS beads. Scanning electron microscope and associated Fourier transform analysis were used to characterize the morphology of the ordered surfaces. Finally, the production of silicon molds is demonstrated by using the beads as a template for dry etching.
In this paper, we report new results on polishing and characterization of thick aluminium nitride (AlN) layers grown on 2-and 3-inch electrically conducting 4H-SiC on-axis substrate. As thick as 10-22 µm AlN layers were deposited on Si-face by stress control hydride vapor phase epitaxy. Rough as-grown layers were polished to provide epi-ready surface for device epitaxy. Surface morphology and surface defects of AlN were studied by atomic force microscopy, optical microscopy and scanning electron microscopy. The root mean square surface roughness was drastically decreased from 470 Å for as-grown surface to less than 3 Å and the peak to valley value was decreased from 345 nm to less than 3 nm. As-grown and polished epilayer thickness homogeneity, verified by Fourier transform infrared (FTIR) reflectivity, is better than 5%. Structural properties were investigated by X-ray diffraction (XRD). XRD rocking curves were measured in ω-scanning mode for the (00.2) and (10.2) reflections. 1 Introduction Semi-insulating low defect substrates are needed for the development and fabrication of high power high frequency GaN-based HEMTs and MMICs. Due to absence of large area native GaN and AlN substrates and thanks to the high thermal conductivity of SiC, the most advanced GaN HEMTs have been demonstrated on semi-insulating SiC substrates. However, semi-insulating SiC substrates have several significant limitations for GaN and AlN epitaxy including technical and economical factors. In this paper, we describe properties of alternative semi-insulating substrate materials for high power GaNbased devices, based on excellent insulating properties of AlN. Thick crack-free AlN epilayers were grown on 2-and 3-inch electrically conducting 4H-SiC on-axis substrates by stress control hydride vapor phase epitaxy (SC HVPE). Since as-grown AlN epilayers are rough, especially thick epilayers, a polishing process was developed. Surface morphology and surface defects were studied with atomic force microscopy (AFM), optical microscopy (Nomarski contrast) and scanning electron microscopy (SEM). Moreover, the epilayer thickness homogeneity was checked by FTIR reflectivity measurements after growth and after polishing. Fabricated substrates were characterized using X-ray diffraction techniques including X-ray rocking curve -scan measurements for both (00.2) and (10.2) AlN reflections.
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