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A realistic topological p-n junction at the Bi2Se3 （0001） surface based on planar twin boundary defects

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Nano Research 2017年第5期10卷 1784-1793页

作者： Hugo Aramberri M. Carmen Munoz Jorge I. Cerda Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) Cantoblanco Madrid 28049 Spain

We propose a realistic topological p-n junction （TPNJ） by matching two Bi2Se3 （0001） slabs with opposite arrangements of planar twin boundary defects. The atomistic modeling of such a device leads to dislocation defects in the hexagonal lattice in several quintuple layers. Nevertheless, total energy calculations reveal that the interface relaxes, yielding a smooth geometrical transition that preserves the nearest-neighbors fcc-type geometry throughout these defect layers. The electronic, magnetic, and transport properties of the junction have then been calculated at the ab initio level under open boundary conditions, i.e., employing a thin-film geometry that is infinite along the electron transport direction. Indeed, a p-n junction is obtained with a built-in potential as large as 350 meV. The calculations further reveal the spin texture across the interface with unprecedented detail. As the main result, we obtain non-negligible transmission probabilities around the F point, which involve an electron spin-flip process while crossing the interface.

关键词： topological insulators,p-n junctions,spintronics,electronic devices,twin boundaries

Strain engineering in single-,bi-and tri-layer MoS_(2),MoSe_(2),WS_(2)and WSe_(2)

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Nano Research 2021年第6期14卷 1698-1703页

作者： Felix Carrascoso Hao Li Riccardo Frisenda Andres Castellanos-Gomez Materials Science Factory Instituto de Ciencia de Materiales de MadridConsejo Superior de Investigaciones Cientificas28049MadridSpain

Strain is a powerful tool to modify the optical properties of semiconducting transition metal dichalcogenides like MoS_(2),MoSe_(2),WS_(2) and WSe_(2).In this work we provide a thorough description of the technical details to perform uniaxial strain measurements on these two-dimensional semiconductors and we provide a straightforward calibration method to determine the amount of applied strain with high accuracy.We then employ reflectance spectroscopy to analyze the strain tunability of the electronic properties of single-,bi-and tri-layer MoS_(2),MoSe_(2),WS_(2) and WSe_(2).Finally,we quantify the flake-to-flake variability by analyzing 15 different single-layer MoS_(2) flakes.

关键词： two-dimensional(2D)materials transition metal dichalcogenides strain engineering band gap differential reflectance

Nanomechanical hydrodynamic force sensing using suspended microfluidic channels

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微系统与纳米工程(英文) 2023年第3期9卷 95-102页

作者： Alberto Martín-Pérez Daniel Ramos Optomechanics Lab Instituto de Ciencia de Materiales de Madrid(ICMMCSIC)3 Sor Juana Inés de la Cruz(Madrid)E-28049 MadridSpain

Microfluidics has demonstrated high versatility in the analysis of in-flow particles and can even achieve mechanical properties measurements of biological cells by applying hydrodynamic forces.However,there is currently no available technique that enables the direct measurement and tracking of these hydrodynamic forces acting on a flowing particle.In this work,we introduce a novel method for the direct measurement of the hydrodynamic force actuating on an in-flow particle based on the analysis of the induced resonance changes of suspended microchannel resonators(SMRs).This hydrodynamic force sensitivity depends on the device used;therefore,we considered the geometry and materials to advance this dependency on the SMR resonance frequency.

关键词： hydrodynamic applying flow

The effect of rippling on the mechanical properties of graphene

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Nano Materials Science 2022年第1期4卷 18-26页

作者： Guillermo Lopez-Polin Cristina Gomez-Navarro Julio Gomez-Herrero Instituto de Ciencia de Materiales de Madrid CSICMadrid E 28049Spain departamento de Física de La Materia Condensada Universidad Autónoma de MadridMadridE-28049Spain IFIMAC Condensed Matter Physics Center(IFIMAC).Universidad Autónoma de madrid MadridE-28049Spain

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very bendable.Consequently, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient(TEC) of free-standing graphene.We also observed an increase of the Young's modulus with global applied strain and with the introduction of small density defects that we attributed to the decrease of rippling. Here, we will focus on a surprising feature observed in the data: the experiments consistently indicate that only the rippling with wavelengths between 5 and 10 nm influences the mechanics of graphene. The rippling responsible of the negative TEC and anomalous elasticity is thought to be dynamic, i.e. flexural phonons. However, flexural phonons with these wavelengths should have minor effects on the mechanics of graphene, therefore other mechanisms must be considered to address our observations. We propose static ripples as one of the key elements to correctly understand the thermomechanics of graphene and suggest that rippling arises naturally due to a competition of symmetry breaking and anharmonic fluctuations.

关键词： Graphene Mechanical properties Atomic force microscopy defects Ripples Stmain

Towards efficient strain engineering of 2D materials:A four-points bending approach for compressive strain

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Nano Research 2024年第6期17卷 5317-5325页

作者： Hao Li Félix Carrascoso Ana Borrás Gloria P.Moreno Francisco J.Aparicio Ángel Barranco Andrés Castellanos Gómez Campus de Cantoblanco Instituto de Ciencia de Materiales de MadridC.Sor Juana Inés de la Cruz328049 MadridSpain Nanotechnology on Surfaces and Plasma Lab Instituto de Ciencia de Materiales de Sevilla(CSIC-Universidad de Sevilla).C/Americo Vespucio 49E-41092 SevilleSpain departamento de Física Aplicada I Escuela Politécnica SuperiorUniversidad de Sevillac/Virgen deÁfrica 7E-41011 SevilleSpain

Strain engineering,as a powerful strategy to tune the optical and electrical properties of two-dimensional(2D)materials by deforming their crystal lattice,has attracted significant interest in recent years.2D materials can sustain ultra-high strains,even up to 10%,due to the lack of dangling bonds on their surface,making them ideal brittle solids.This remarkable mechanical resilience,together with a strong strain-tunable band structure,endows 2D materials with a broad optical and electrical response upon strain.However,strain engineering based on 2D materials is restricted by their nanoscale and strain quantification troubles.In this study,we have modified a homebuilt three-points bending apparatus to transform it into a four-points bending apparatus that allows for the application of both compressive and tensile strains on 2D materials.This approach allows for the efficient and reproducible construction of a strain system and minimizes the buckling effect caused by the van der Waals interaction by adamantane encapsulation strategy.Our results demonstrate the feasibility of introducing compressive strain on 2D materials and the potential for tuning their optical and physical properties through this approach.

关键词： uniaxial compressive strain polymer encapsulation differential reflectance spectroscopy exciton tunability

The complex Maxwell stress tensor theorem:The imaginary stress tensor and the reactive strength of orbital momentum.A novel scenery underlying electromagnetic optical forces

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Light(Science & Applications) 2022年第11期11卷 2655-2675页

作者： Manuel Nieto-Vesperinas Xiaohao Xu Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Cintificas.Campus de CantoblancoMadrid 28049Spain State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi'an 710119China Institute of Nanophotonics Jinan UniversityGuangzhou 511443China

We uncover the existence of a universal phenomenon concerning the electromagnetic optical force exerted by light or other electromagnetic waves on a distribution of charges and currents in general,and of particles in particular.This conveys the appearence of underlying reactive quantities that hinder radiation pressure and currently observed timeaveraged forces.This constitutes a novel paradigm of the mechanical effciency of light on matter,and completes the landscape of the optical,and generally electromagnetic,force in photonics and classical electrodynamics;widening our understanding in the design of both llumination and particles in optical manipulation without the need of increasing the illuminating power,and thus lowering dissipation and heating.We show that this may be accomplished through the minimization of what we establish as the reactive strength of orbital(or canonical)momentum,which plays against the optical force a role analogous to that of the reactive power versus the radiation effciency of an antenna.This long time overlooked quantity,important for current progress of optical manipulation,and that stems from the complex Maxwell theorem of conservation of complex momentum that we put forward,as well as its alternating flow associated to the imaginary part of the complex Maxwell stress tensor,conform the imaginary Lorentz force that we introduce in this work,and that like the reactive strength of orbital momentum,is antagonistic to the well-known time-averaged force;thus making this reactive Lorentz force indirectly observable near wavelengths at which the time-averaged force is lowered.The Minkowski and Abraham momenta are also addressed.

关键词： imaginary tensor orbital

Laser trimming for lithography-free fabrications of MoS_(2)devices

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Nano Research 2023年第4期16卷 5042-5046页

作者： Yong Xie OnurÇakıroğlu Wenshuai Hu Kexin He Sergio Puebla Thomas Pucher Qinghua Zhao Xiaohua Ma Carmen Munuera Andres Castellanos-Gomez Key Laboratory of Wide Band-Gap Semiconductor Technology School of Advanced Materials and NanotechnologyXidian UniversityXi’an 710071China Materials Science Factory Instituto de Ciencia de Materiales de MadridConsejo Superior de Investigaciones Científicas28049 MadridSpain

Single-layer MoS_(2)produced by mechanical exfoliation is usually connected to thicker and multilayer regions.We show a facile laser trimming method to insulate single-layer MoS_(2)regions from thicker ones.We demonstrate,through electrical characterization,that the laser trimming method can be used to pattern single-layer MoS_(2)channels with regular geometry and electrically disconnected from the thicker areas.Scanning photocurrent microscope further confirms that in the as-deposited flake(connected to a multilayer area)most of the photocurrent is being generated in the thicker flake region.After laser trimming,scanning photocurrent microscopy shows how only the single-layer MoS_(2)region contributes to the photocurrent generation.The presented method is a direct-write and lithography-free(no need of resist or wet chemicals)alternative to reactive ion etching process to pattern the flakes that can be easily adopted by many research groups fabricating devices with MoS_(2) and similar twodimensional materials.

关键词： 2D materials transition metal dichalcogenides laser trimming differential reflectance

Pyrenetetraone-based covalent organic framework as an effective electrocatalyst for oxygen reduction reaction

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Nano Research 2022年第5期15卷 3907-3912页

作者： Paloma Garcia-Arroyo Emiliano Martinez-Perinan Jorge J.Cabrera-Trujillo Elena Salagre Enrique G.Michel Jose I.Martinez Encarnacion Lorenzo Jose L.Segura departamento de Quimica Organica I Facultad de CC.QuimicasUniversidad Complutense de Madrid28040 MadridSpain departamento de Quimica Analitica y Analisis Instrumental Facultad de CienciasUniversidad Autónoma de Madrid28049 MadridSpain departamento de Fisica de la Materia Condensada Universidad Autónoma de Madrid28049 MadridSpain Condensed Matter Physics Center(IFIMAC) Universidad Autónoma de Madrid28049 MadridSpain departamento de Nanoestructuras SuperficiesRecubrimientos y Astrofisica MolecularInstituto de Ciencia de Materiales de Madrid(ICMMCSIC)28049 MadridSpain instituto Madrileno de Estudios Avanzados en Nanociencia(IMdeA-Nanociencia) 28049 MadridSpain Institute for Advanced Research in Chemical Sciences(IAdChem) Universidad Autonoma de Madrid28049 MadridSpain

A novel porous and crystalline two-dimensional(2D)electrochemically active covalent organic framework(COF)based on ortho-quinone units has been prepared as an innovative approach towards the development of organic cathode materials with multiple redox sites as an efficient electrocatalyst for the oxygen reduction reaction(ORR).In contrast with most of the previously reported COFs as electrocatalysts for the ORR,the electrocatalytic application of this material towards ORR has been investigated without adding any metal or conductive supporting material and avoiding any additional carbonization step.Additionally,the electrochemical properties of the COF material have been compared with two analogue amorphous frameworks with similar chemical composition,which points out the important role of the enhanced crystallinity and porosity of the COF network in its superior performance as an electrocatalyst towards ORR.

关键词： electrocatalysis oxygen reduction reaction metal free pyrenetetraone covalent organic framework

Ca-based materials derived from calcined cigarette butts for CO_(2)capture and thermochemical energy storage

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Journal of Environmental Sciences 2024年第6期140卷 230-241页

作者： Nabil Amghar Virginia Moreno Pedro E.Sánchez-Jiménez Antonio Perejón Luis A.Pérez-Maqueda instituto de ciencia de materiales de Sevilla C.S.I.C.-Universidad de SevillaC.Américo Vespucio4941092 SevillaSpain instituto de Tecnología de materiales(ITM) Universitat Politècnica de València(UPV)Plaza Ferrándiz y Carbonell 1AlcoyAlicante 03801Spain departamento de Química Inorgánica Facultad de QuímicaUniversidad de Sevilla41012 SevillaSpain

Cigarette butts(CBs)are one of the most common types of litter in the world.Due to the toxic substances they contain,the waste generated poses a harmful risk to the environment,and therefore there is an urgent need for alternative solutions to landfill storage.Thus,this work presents a possible revalorization of this waste material,which implies interesting environmental benefits.CBs were used as sacrificial templates for the preparation of CaO-based materials by impregnation with calcium and magnesium nitrates followed by flaming combustion.These materials presented enhanced porosity for their use in the Calcium Looping process applied either to thermochemical energy storage or CO_(2)capture applications.The influence of the concentration of Ca and Mg in the impregnating solutions on the multicycle reactivity of the samples was studied.An improved multicycle performance was obtained in terms of conversion for both applications.

关键词： Cigarette butts Calcium-Looping CO_(2)Capture Thermochemical energy storage