Interest in layered van der Waals semiconductor gallium monosulfide (GaS) is growing rapidly because of its wide band gap value between those of two-dimensional transition metal dichalcogenides and of insulating layered materials such as hexagonal boron nitride. For the design of envisaged optoelectronic, photocatalytic and photonic applications of GaS, the knowledge of its dielectric function is fundamental. Here we present a combined theoretical and experimental investigation of the dielectric function of crystalline 2H-GaS from monolayer to bulk. Spectroscopic imaging ellipsometry with micron resolution measurements are corroborated by first principle calculations of the electronic structure and dielectric function. We further demonstrate and validate the applicability of the established dielectric function to the analysis of the optical response of c-axis oriented GaS layers grown by chemical vapor deposition (CVD). These optical results can guide the design of novel, to our knowledge, optoelectronic and photonic devices based on low-dimensional GaS.
Hot-carrier based photodetectors and enhanced by surface plasmons (SPs) hot-electron injection into semiconductors, are drawing significant attention. This photodetecting strategy yields to narrowband photoresponse while enabling photodetection at sub-bandgap energies of the semiconductor materials. In this work, we analyze the design of a reconfigurable photodetector based on a metal-semiconductor (MS) configuration with interdigitated dual-comb Au electrodes deposited on the semiconducting Sb2S3 phase-change material. The reconfigurability of the device relies on the changes of refractive index between the amorphous and crystalline phases of Sb2S3 that entail a modulation of the properties of the SPs generated at the dual-comb Au electrodes. An exhaustive numerical study has been realized on the Au grating parameters formed by the dual-comb electrodes, and on the SP order with the purpose of optimizing the absorption of the device, and thus, the responsivity of the photodetector. The optimized photodetector layout proposed here enables tunable narrowband photodetection from the O telecom band (λ = 1310 nm) to the C telecom band (λ = 1550 nm).
All-dielectric metasurfaces are a blooming field with a wide range of new applications spanning from enhanced imaging to structural color, holography, planar sensors, and directionality scattering. These devices are nanopatterned structures of sub-wavelength dimensions whose optical behavior (absorption, reflection, and transmission) is determined by the dielectric composition, dimensions, and environment. However, the functionality of these metasurfaces is fixed at the fabrication step by the geometry and optical properties of the dielectric materials, limiting their potential as active reconfigurable devices. Herein, a reconfigurable all-dielectric metasurface based on two high refractive index (HRI) materials like silicon (Si) and the phase-change chalcogenide antimony triselenide (Sb2Se3) for the control of scattered light is proposed. It consists of a 2D array of Si–Sb2Se3–Si sandwich disks embedded in a SiO2 matrix. The tunability of the device is provided through the amorphous-to-crystalline transition of Sb2Se3. We demonstrate that in the Sb2Se3 amorphous state, all the light can be transmitted, as it is verified using the zero-backward condition, while in the crystalline phase most of the light is reflected due to a resonance whose origin is the contribution of the electric (ED) and magnetic (MD) dipoles and the anapole (AP) of the nanodisks. By this configuration, a contrast in transmission (ΔT) of 0.81 at a wavelength of 980 nm by governing the phase of Sb2Se3 can be achieved.
Active materials which show phase transitions, usually known as Phase Change Materials (PCM), have paved the way to a new generation of reconfigurable plasmonic platforms. Tunable color devices have experienced a great development in the recent years. In particular, reflective color filters can take advantage from sunlight to select and reflect a specific resonant wavelength in the visible spectrum range. Reflective displays are usually structural color filters based on asymmetric Fabry-Perot cavities (AFPCs). For a fixed geometry, most of AFPCs filters generate static color, limiting their potential as tunable color devices. Dynamic color is achieved by introducing an active layer whose optical properties can be modulated by an external stimuli. In this paper, we propose AFPCs based on molybdenum oxide (MoO x , 2<x<3) to achieve switchable on/off color reflective pixels. On and off states of the pixels are controlled through the stoichiometry of the MoO x layer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.