Metallic Edge Research Articles

A DFT study of site-dependent energetics of hexagonal MoS[formula omitted] nanoparticles under varying reaction conditions

A plane wave periodic density functional theory study of a representative hexagonal shaped MoS2 nanoparticle is conducted to compute the site-dependent energetics of the catalyst under different operating conditions. It is shown that the (1) energy for vacancy formation and the associated free energy profile of the reaction steps involved in creating the vacancy and (2) the binding energy of hydrogen and other probe atoms such as CO and lutidine, are all dependent on the location of the associated sulfur or molybdenum atom and the edge type (i.e. metal or sulfur edge). In particular, sulfur atoms near the corner are more strongly bound than those in the interior of the metal edge. Further, a larger metal-sulfur bond strength results in lower binding energy of hydrogen on that sulfur atom which in turn implies that this hydrogen is more Brønsted acidic in nature. These results indicate that the nature and the location of active sites on MoS2 is heavily dependent on the nature of the reaction that is being catalyzed and the corresponding operating conditions.

Two-dimensional obstructed atomic insulators with fractional corner charge in the MA2Z4 family

According to topological quantum chemistry (TQC), a class of electronic materials has been called obstructed atomic insulators (OAIs), in which a portion of valence electrons necessarily have their centers located on some empty Wyckoff positions (WPs) without atom occupation in the lattice. The obstruction of centering these electrons coinciding with their host atoms is nontrivial and results in metallic boundary states when the boundary is properly cut. Here, on the basis of first-principles calculations in combination with TQC analysis, we propose two-dimensional ${MA}_{2}{Z}_{4}$ $(M=\mathrm{Cr}, \mathrm{Mo}, and \mathrm{W}; A=\mathrm{Si} \mathrm{and} \mathrm{Ge}; Z=\mathrm{N}, \mathrm{P}, \mathrm{and} \mathrm{As})$ monolayers are all OAIs. A typical case is the recently synthesized ${\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ (${\ensuremath{\alpha}}_{1}\text{\ensuremath{-}}{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$). Although both ${\ensuremath{\alpha}}_{1}$- and ${\ensuremath{\alpha}}_{2}\text{\ensuremath{-}}{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ monolayers are topological trivial insulators, it has valence electrons centering empty WPs and the in-gap corner states at the three vertices of triangle-shaped nanodisk samples respecting ${C}_{3}$ rotation symmetry, which can be explained by the filling anomaly of electrons. In addition, the ${\ensuremath{\alpha}}_{2}\text{\ensuremath{-}}{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ monolayer exhibits unique OAI-induced metallic edge states along the $(1\overline{1})$ edge. The readily synthesized ${\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ is quite stable and has a large bulk bandgap of 1.94 eV, which makes the identification of these edge and corner states most possible for experimental clarification.

Enhanced Oxide Reduction by Hydrogen at Cuprous Oxide–Copper Interfaces near Ascending Step Edges

Understanding the dynamic processes involved in the interaction of hydrogen with oxides is of fundamental importance in catalysis. This paper probes the reduction of Cu2O-“29” surfaces by hydrogen at room temperature combining in situ ambient pressure scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Reduction of the atomic layer thin Cu2O film is observed to be preferentially initiated at step edges and terrace defects, where perfect Cu2O(111) terraces are found to be stable toward hydrogenation under the same conditions. After a long induction period, regions of partially reduced Cu2O-“29” and metallic Cu coexist before the surface is fully reduced to Cu(111). The reduction rate strongly depends on the nature of nearby Cu step edges. We propose a mechanism for the reduction of Cu2O-“29” by hydrogen where free copper atoms from ascending metallic step edges facilitate the formation of active ensembles for H2 dissociation and transfer H to the edges of Cu2O regions.

P‐5.3: Customization of Metal Wire Taper Specifications

GE(M1) and SE (M2) two metal film layers need to be patterned by wet etching solution. If the taper is too high after etching, it will lead to light leakage from the metal edge, which will reduce the contrast (GE only) and poor coverage of the insulating layer. If it is too low, the resistance value of the fanout will change greatly, and the photoresist will fall and lead to the failure of the metal line. In this article, we mainly analyze how to develop the specification of the taper for GE/SE layer metal wet etchant.

Proximity-magnetized quantum spin Hall insulator: monolayer 1 T’ WTe2/Cr2Ge2Te6

Van der Waals heterostructures offer great versatility to tailor unique interactions at the atomically flat interfaces between dissimilar layered materials and induce novel physical phenomena. By bringing monolayer 1 T’ WTe2, a two-dimensional quantum spin Hall insulator, and few-layer Cr2Ge2Te6, an insulating ferromagnet, into close proximity in an heterostructure, we introduce a ferromagnetic order in the former via the interfacial exchange interaction. The ferromagnetism in WTe2 manifests in the anomalous Nernst effect, anomalous Hall effect as well as anisotropic magnetoresistance effect. Using local electrodes, we identify separate transport contributions from the metallic edge and insulating bulk. When driven by an AC current, the second harmonic voltage responses closely resemble the anomalous Nernst responses to AC temperature gradient generated by nonlocal heater, which appear as nonreciprocal signals with respect to the induced magnetization orientation. Our results from different electrodes reveal spin-polarized edge states in the magnetized quantum spin Hall insulator.

Critical Importance of Nonuniform Polarization and Fringe Field Effects for Scaled Ferroelectric FinFET Memory

The ferroelectric field-effect transistor (FEFET) is an emerging nonvolatile memory technology that can offer ultra-scalability, fast operation, and reduced power consumption. However, a limited understanding of FEFET physics poses challenges for optimum device design. In this article, we provide physical insights into the operation of FinFET-based FEFETs (FEFinFETs) using a phase-field framework built on time-dependent Landau–Ginzburg (TDGL) thermodynamic theory. We exploit the source–drain fringing field to stabilize a monodomain configuration in the OFF state of short channel FEFinFETs. Based on recent experiments, we first analyze the switching dynamics of FEFinFETs with low remnant polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{r}$ </tex-math></inline-formula> ) and high coercive field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{c}$ </tex-math></inline-formula> ) hafnium zirconium oxide (HZO) FE. We find that the switching in these FEFinFETs occurs via domain nucleation and growth from the gate metal edges at the source–drain spacers. We also show that a non-zero drain bias can be used for dynamically modulating the memory window (MW) of FEFinFET to lower its power consumption. Furthermore, we find the spacer permittivity to be a crucial design parameter to control the MW and show that a lower spacer permittivity can significantly increase the MW. Finally, we show that the commonly held idea that a large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{r}$ </tex-math></inline-formula> leads to a large MW is not always valid. For a large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{r}$ </tex-math></inline-formula> , the formation of multiple domains in the FE layer can lead to a significant reduction in the MW. In addition, these devices can suffer from low write endurance due to exposure of the interfacial oxide layer to high electric fields.

Interplay between edge states and charge density wave order in the Falicov-Kimball model on a Haldane ribbon

To determine the impact of including edge states on the phase diagram of a spinless Falicov-Kimball model on the Haldane lattice, a study of a corresponding ribbon geometry with zigzag edges is conducted. By varying the ribbon widths, the distinction between the effects connected to the mere presence of the edges and those originating from interference between the edge states is established. The local doping caused by the former is shown to give rise to a topologically trivial bulk insulator with metallic edge states. Additionally, it gives rise to a charge density wave (CDW) phase with mixed character of the subbands in various parts of the phase diagram. The impact of local doping on the CDW instability is also addressed. Two additional gapless phases are found, caused by the edges but with stability regions depending on the width of the ribbon.

Direct probing of temperature-independent bulk half-metallicity in Co2MnSi by spin-resolved hard x-ray photoemission

We have performed the bulk-sensitive spin-resolved hard x-ray photoelectron spectroscopy (HAXPES) to directly clarify the spin-dependent valence band electronic states and spin polarization of $L{2}_{1}$-ordered ${\mathrm{Co}}_{2}\mathrm{MnSi}$ as a predicted half-metal. The spin-resolved valence band HAXPES spectra clearly exhibited the difference in the majority and minority spin states in the bulk region of a 30-nm-thick ${\mathrm{Co}}_{2}\mathrm{MnSi}(001)$ thin film buried under a MgO(2 nm) layer at both temperatures of 21 and 300 K. As expected from the half-metallicity in ${\mathrm{Co}}_{2}\mathrm{MnSi}$, we found that the majority (minority) spin spectrum shows a metallic Fermi edge (a band gap), leading the high spin polarization of \ensuremath{\sim}90% at around the Fermi level at a temperature of 21 K. The spin-resolved HAXPES experiments revealed that the half-metallicity of ${\mathrm{Co}}_{2}\mathrm{MnSi}$ in the bulk region is independent on the temperature up to 300 K. The experiments also revealed the slight changes in the majority spin spectral shapes and the shift of the valence band maximum of the minority spin states with temperature. By comparing the experimental results with the first-principles calculations at a finite temperature obtained by the disordered local moment method, it is suggested that the slight changes in the majority and minority spin HAXPES spectra of ${\mathrm{Co}}_{2}\mathrm{MnSi}$ with temperature is mainly caused by the temperature-dependent Co $3d$ electronic states. It is also suggested that the conduction band minimum of the minority spin states is located sufficiently above the Fermi level at temperature up to 300 K.

Hydrothermal Synthesis of Non-noble Hybrid Cu2S Decorated Nickel Foam and Its Enhanced Electrocatalytic Activity for Direct Aluminum Fuel Cell Application

Recycling of aluminum metal from scrap materials demands a high processing temperature, which releases several toxic gases to the environment. In contrast, aluminum metal is known as the cleanest and cheapest source for hydrogen production because of its 3+ oxidation state and spontaneous exothermic reaction with water molecules. In this work, we report the hydrothermal synthesis of hybrid Cu2S decorated on nickel foam (NF) for direct aluminum fuel cell application. The hybrid structure of the Cu2S nanoflake- and nanosphere-based catalyst distributed on the three-dimensional (3D) skeletal NF is revealed via detailed structural analysis. The Cu2S/NF-8 catalyst electrode exhibits a maximum mass activity of 106.7 mA/mg at an overpotential of 0.8 V (vs Hg/HgO) for a 40 mg Al source. The high mass activity of the optimized Cu2S/NF-8 catalyst electrode is attributed to the hybrid Cu2S structure, which facilitates improved electrocatalytic activity via its point defects and metallic edges. Likewise, the high electrical conductivity, chemical stability, and rapid charge transfer at the electrode with a short diffusion path are because of the arrangements of the hybrid Cu2S on the NF substrate. The stability and real-time performance of the Cu2S/NF-8 catalyst electrode is successfully studied via chronoamperometry in the presence of an Al ball and a scrap aluminum source. The electrode exhibits a capacity retention of ∼60% (for 7000 s; Al ball) and ∼35% (for 100000 s; scrap Al). This proves the Cu2S/NF-8 catalyst electrode as a promising platform for aluminum source-based fuel cell applications.

Ab Initio Properties of Hybrid Cove-Edged Graphene Nanoribbons as Metallic Electrodes for Peptide Sequencing via Transverse Tunneling Current.

Recently synthesized metallic cove-edged graphene nanoribbons are considered for use as one-dimensional (1D) electrodes for ideal atomistically resolved recognition of amino acids. To this purpose a narrow nanogap device is considered, and the transversal tunneling current flowing across it is calculated during the translocation of a model Gly homopeptide using the nonequilibrium Green function scheme, based on density functional theory. We show that the signal collected from the metallic spin states is characterized by a double peak per residue in analogy with the results obtained with 1D graphene nanoribbon template electrodes. The presented results pave the way for experimentally feasible atomistically resolved tunneling current recognition using metallic edge engineered graphene electrodes obtained by bottom-up fabrication strategies.

An Edge Detection Method Based on Local Gradient Estimation: Application to High-Temperature Metallic Droplet Images

Edge detection is a fundamental step in many computer vision systems, particularly in image segmentation and feature detection. There are a lot of algorithms for detecting edges of objects in images. This paper proposes a method based on local gradient estimation to detect metallic droplet image edges and compare the results to a contour line obtained from the active contour model of the same images, and to results from crowdsourcing to identify droplet edges at specific points. The studied images were taken at high temperatures, which makes the segmentation process particularly difficult. The comparison between the three methods shows that the proposed method is more accurate than the active contour method, especially at the point of contact between the droplet and the base. It is also shown that the reliability of the data from the crowdsourcing is as good as the edge points obtained from the local gradient estimation method.

TCAD study of high breakdown voltage AlGaN/GaN HEMTs with embedded passivation layer

The breakdown characteristics of AlGaN/GaN high-electron-mobility transistors are one of the most important parameters for practical applications when used as power devices. In this study, the relationship between the relative permittivity of the passivation layers and the breakdown voltages in the off state was investigated in detail using TCAD simulations. An embedded double-passivation layer was proposed to enhance the breakdown voltage of the devices. This device structure was realized using an additional step of etching and opening holes on the edge of the gate metal, followed by the deposition of the embedded passivation films. The extracted electric field shows that this embedded passivation layer not only can improve the breakdown characteristics of the device like using a single high-k passivation film but also presents as the function of the ‘Metal Field Plate’, additionally resulting in the enlarged breakdown voltage. Further theoretical simulations indicated that the greater the difference between the dielectric constants of the high/low passivation materials, the higher the breakdown voltage can be obtained.

(Invited, Digital Presentation) Exploring the Potential and Limits of Gallium Oxide Electronics: In-Situ Dielectrics, Heterointegration and High-k Field Plates

The intrinsic properties of beta phase Gallium Oxide such as the high breakdown field strength makes it a very attractive material for next generation electronics. Rapid progress has been made over the last few years in pushing the performance of Gallium Oxide-based vertical Schottky diodes and lateral field effect transistors and impressive figure of merit has been reported. However, the device performance is farther from the expected performance based on intrinsic properties. Exploration of the intrinsic potential is rather limited by several factors such as the quality of dielectrics and dielectric/semiconductor interfaces, electric field management challenges due to the lack of p-type material, to name a few. In this work, we will highlight a few approaches to tackle some of these challenges.(1) In-situ dielectrics: High quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. We report in situ metal–organic chemical vapor deposition of Al2O3 on β-Ga2O3 as a potentially better alternative to the most commonly used atomic layer deposition (ALD) [1]. The growth of Al2O3 is performed in the same reactor as Ga2O3 using trimethylaluminum and O2 as precursors without breaking the vacuum at a growth temperature of 600 °C. The fast and slow near interface traps at the Al2O3/β-Ga2O3 interface are identified and quantified using stressed capacitance–voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (Dit) are measured using ultraviolet-assisted CV technique. The average Dit for the MOSCAP is determined to be 6.4 × 1011 cm−2eV−1. The conduction band offset of the Al2O3/ Ga2O3 interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al2O3/Ga2O3 interface. The current–voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV cm−1.(2) Field management using High-K field Plate: We report a vertical (001) β-Ga2O3 field-plated (FP) Schottky barrier diode (SBD) with a novel extreme permittivity dielectric field oxide [2] . A thin drift layer of 1.7μm was used to enable a punch-through (PT) field profile and very low differential specific on-resistance (Ron-sp) of 0.32 mΩ-cm2. The extreme permittivity field plate oxide facilitated the lateral spread of the electric field profile beyond the field plate edge and enabled a breakdown voltage (Vbr) of 687 V. The edge termination efficiency increases from 13.2%for non-field plated structure to 61% for high permittivity field plate structure. The high permittivity field plated SBD demonstrated a record high Baliga's figure of merit (BFOM) of 1.47 GW/cm2 showing the potential of Ga2O3 power devices for multi-kilovolt class applications.(3) p-type III-nitride/Ga2O3 integration for field management: This work presents the simulation and analysis of a novel Ga 2 O 3 vertical Schottky diode with three different guard ring (GR) configurations to reduce the peak electric field at the metal edges [3]. Highly doped p-type GaN, p-type nonpolar AlGaN, and polarization-doped graded p-AlGaN are simulated and analyzed as the GR material, which forms a heterojunction with the Ga 2 O 3 drift layer. GR with nonpolar graded p-AlGaN with a bandgap larger than Ga 2 O 3 is found to show the best performance in terms of screening the electric field at the metal edges. The proposed GR configuration is also compared with a reported Ga 2 O 3 Schottky diode with no GR and a structure with high-resistive nitrogen-doped GR. The optimized design is predicted to have a breakdown voltage as high as 6.2 kV and a specific ON-resistance of 3.55 mΩ-cm 2, which leads to an excellent power figure of merit of 10.8 GW/cm 2.The approaches discussed here can offer a pathway towards understanding the true potential and limitations of Gallium Oxide for extreme electric field devices. We acknowledge funding support from NSF (DMR-1931652) and the AFOSR MURI program (FA9550-18-1-0507).

Band Polarization Effect on the Kondo State in a Zigzag Silicene Nanoribbon.

Using the Numerical Renormalization Group method, we study the properties of a quantum impurity coupled to a zigzag silicene nanoribbon (ZSNR) that is subjected to the action of a magnetic field applied in a generic direction. We propose a simulation of what a scanning tunneling microscope will see when investigating the Kondo peak of a magnetic impurity coupled to the metallic edge of this topologically non-trivial nanoribbon. This system is subjected to an external magnetic field that polarizes the host much more strongly than the impurity. Thus, we are indirectly analyzing the ZSNR polarization through the STM analysis of the fate of the Kondo state subjected to the influence of the polarized conduction electron band. Our numerical simulations demonstrate that the spin-orbit-coupling-generated band polarization anisotropy is strong enough to have a qualitative effect on the Kondo peak for magnetic fields applied along different directions, suggesting that this contrast could be experimentally detected.

Relativistic Orbital-Optimized Density Functional Theory for Accurate Core-Level Spectroscopy.

Core-level spectra of 1s electrons of elements heavier than Ne show significant relativistic effects. We combine advances in orbital-optimized density functional theory (OO-DFT) with the spin-free exact two-component (X2C) model for scalar relativistic effects to study K-edge spectra of third period elements. OO-DFT/X2C is found to be quite accurate at predicting energies, yielding a ∼0.5 eV root-mean-square error versus experiment with the modern SCAN (and related) functionals. This marks a significant improvement over the >50 eV deviations that are typical for the popular time-dependent DFT (TDDFT) approach. Consequently, experimental spectra are quite well reproduced by OO-DFT/X2C, sans empirical shifts for alignment. OO-DFT/X2C combines high accuracy with ground state DFT cost and is thus a promising route for computing core-level spectra of third period elements. We also explored K and L edges of 3d transition metals to identify limitations of the OO-DFT/X2C approach in modeling the spectra of heavier atoms.

Dissimilar welding of Inconel 713 superalloy and AISI 4140 steel using Nd:YAG pulse laser: An investigation on the microstructure and mechanical properties

In the present research, welding of Inconel 713 superalloy and high strength AISI 4140 steel was successfully implemented by using pulsed Nd:YAG laser. The effect of heat input on the microstructural and mechanical properties of the weld was studied to find the best conditions for achieving a high quality weld. The microstructure characteristics of different weld regions including weld metal and heat affected zone were examined using the optical and scanning electron microscopies. It was observed that a columnar dendritic structure was formed at the edge of weld metal due to higher gradient temperature, while the reduction of gradient at the center of weld metal produced a cellular dendritic structure. The increase of heat input encouraged the formation of coarse dendritic structure which resulted in a reduction in the hardness of weld metal. The HAZ of 4140 steel side showed the maximum hardness for different values of heat inputs due to formation of martensitic microstructure, while the hardness in HAZ of Inconel 713 side was not showed a significant change. The higher value of heat input led to the segregation of Nb, Mo and Ti elements in the inter-dendritic regions and formation of brittle laves phase which resulted in a reduction in the tensile strength. However, the weld joint indicated a maximum tensile strength of 1068 MPa at lower heat input (1875 J/mm). The fracture surface of the tensile specimens showed a brittle fracture in the weld metal at different heat inputs.

Highly Transparent and Polarization-Maintained Terahertz Plasmonic Metamaterials Based on Metal-Wire-Woven Hole Arrays: Fundamentals and Characterization of Transmission Spectral Peaks.

Metal-hole-supported terahertz (THz) waves through the structure of a metal-wire-woven hole array (MWW-HA) present high-frequency-passed transmittance spectra of one plasmonic metamaterial with artificial plasmonic frequencies, which are inversely proportional to metal-hole widths. For the transmitted THz waves of MWW-HA, transverse-electric (TE) and transverse-magnetic (TM) waveguide modes mix within a symmetric metal-hole boundary. THz resonance waves transversely crossing the holes of MWW-HA are experimentally characterized with spectral peaks in the frequency range of 0.1–2 THz that are correlated with aperture sizes, unit-cell-hole widths, metal-wire thicknesses, and wire-bending angles. The metal-hole-transported resonance waves of MWW-HA are dominated by TE waveguide modes instead of TM ones because a hole width of MWW-HA is approximate to the half wavelength of a resonance wave. The round metal edges of the woven metal wires can minimize the effective optical length of a thick metal hole to transmit THz resonance waves, thereby resulting the smallest rotation angle of linear polarization and high transmittance up to 0.94. An MWW-HA structure is therefore reliable for supporting metal-hole resonance waves with low resistance, whereas a metal-slab-perforated hole array cannot achieve the same result.

Manipulating edge current spin polarization in zigzag MoS2 nanoribbons

The electronic structure and quantum transport of a zigzag monolayer molybdenum disulfide (MoS2) nanoribbon are investigated using a six-band tight-binding model. For metallic edge modes, considering both an intrinsic spin–orbit coupling and local exchange field effects, spin degeneracy and spin inversion symmetry are broken and spin selective transport is possible. Our model is a three-terminal field effect transistor with a circular-shaped gate voltage in the middle of scattering region. One terminal measures the top edge current and the other measures the bottom edge current separately. By controlling the circular gate voltage, each terminal can detect a totally spin-polarized edge current. The radius of the circular gate and the strength of the exchange field are important, because the former determines the size of the channel in both S-terminated (top) and Mo-terminated (bottom) edges and the latter is strongly related to unbalancing of the density of spin states. The results presented here suggest that it should be possible to construct spin filters using implanted MoS2 nanoribbons.

Lower Limits of Contact Resistance in Phosphorene Nanodevices with Edge Contacts.

Edge contacts are promising for improving carrier injection and contact resistance in devices based on two-dimensional (2D) materials, among which monolayer black phosphorus (BP), or phosphorene, is especially attractive for device applications. Cutting BP into phosphorene nanoribbons (PNRs) widens the design space for BP devices and enables high-density device integration. However, little is known about contact resistance (RC) in PNRs with edge contacts, although RC is the main performance limiter for 2D material devices. Atomistic quantum transport simulations are employed to explore the impact of attaching metal edge contacts (MECs) on the electronic and transport properties and contact resistance of PNRs. We demonstrate that PNR length downscaling increases RC to 192 Ω µm in 5.2 nm-long PNRs due to strong metallization effects, while width downscaling decreases the RC to 19 Ω µm in 0.5 nm-wide PNRs. These findings illustrate the limitations on PNR downscaling and reveal opportunities in the minimization of RC by device sizing. Moreover, we prove the existence of optimum metals for edge contacts in terms of minimum metallization effects that further decrease RC by ~30%, resulting in lower intrinsic quantum limits to RC of ~90 Ω µm in phosphorene and ~14 Ω µm in ultra-narrow PNRs.

Near-field strong plasmonic resonances in Bi1.5Sb0.5Te1.8Se1.2 topological insulator film

Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They exhibit various novel electronic and optical properties that make them highly promising electronic, spintronic, and optoelectronic materials. Our report confirms that the topological insulator Bi1.5Sb0.5Te1.8Se1.2 (BSTS) is also an effective plasmonic material in the visible and near-infrared range. A BSTS film can effectively control transmission and reflection characteristics by changing the period of the hole array. This study determined that a strong resonant surface plasmonic mode at the resonance peak can confine approximately 80% of the electromagnetic field energy is demonstrated. Higher-order (second- and third-order) resonance peaks were also found, which is critical for controlling electromagnetic waves and research into new optoelectronic devices.