Substrate-enhanced and subsurface infrared near-field spectroscopy of organic layers

112 p.La nano-espectroscopía infrarroja, basada en espectroscopía de transformada de Fourier de campo cercano (nano-FTIR), es una herramienta potente que permite la identificación química de materiales con una resolución espacial nanométrica. Sin embargo, hay muchas preguntas abiertas y desafíos relacionados con la técnica nano-FTIR. Por un lado, detectar una capa molecular de espesor nanométrico depositada sobre un sustrato estándar utilizado en espectroscopía infrarroja (como CaF2) es complicado debido a las débiles señales de nano-FTIR. Por otro lado, la capacidad de la utilización de la técnica nano-FTIR para analizar materiales subsuperficiales es un terreno que ha sido poco explorado. En esta tesis se demuestra, en primer lugar, que hay un aumento significativo en la señal al colocar la capa molecular sobre sustratos altamente reflectantes como el silicio o el oro.Además, se observa que hay un aumento en la señal al explotar el mecanismo de acoplamiento entre la punta y los polaritones del sustrato, y por iluminar la punta con polaritones de superficie. El aumento en la señal es alrededor de dos órdenes de magnitud sobre un sustrato de cuarzo fonón-polaritónico, en comparación a la señal obtenida sobre el sustrato de CaF2. En segundo lugar, se presenta la espectroscopía nano-FTIR de capas orgánicas subsuperficiales, en la que se observa que los espectros nano-FTIR de capas superficiales delgadas difieren de los espectros de las capas subsuperficiales del mismo material orgánico. Asimismo, se estudia la correlación de las diferentes características de los picos obtenidos por nano-FTIR, y se establece una metodología simple y robusta capaz de distinguir capas superficiales de capas subsuperficiales. Los resultados obtenidos son fundamentalmente importantes para impulsar la espectroscopía nano-FTIR hacia la detección rutinaria de monocapas y moléculas individuales y, además, para la interpretación de los espectros nano-FTIR de muestras multicapa, en particular para evitar que los cambios en los picos espectrales inducidos por la geometría se expliquen mediante efectos químicos.-Infrared nanospectroscopy based on Fourier transform infrared near-field spectroscopy (nano-FTIR) is an emerging nanoanalytical tool with large application potential for label-free chemical characterization of organic and inorganic composite surfaces. However, there are many open questions and challenges related to nano-FTIR. On the one hand, the detection of thin organic layers is still challenged by weak nano-FTIR signals, when the organic layer is placed on standard substrates such as CaF2. On the other hand, the potential capability of nano-FTIR for subsurface material analysis is still largely unexplored terrain. In this thesis, it is first demonstrated that a significant enhancement of the nano-FTIR signal from a thin organic layer is obtained by placing the organic layer on highly reflecting substrates such as silicon or gold. An even further signal enhancement is demonstrated by exploiting polariton-resonant tip-substrate coupling and surface polariton illumination of the nano-FTIIR probing tip. A signal enhancement of up to nearly two orders of magnitude is achieved on a polaritonic quartz substrate, as compared to the standard IR substrate CaF2. Secondly, it is demonstrated that nano-FTIR spectroscopy of subsurface organic layers is possible, revealing that nano-FTIR spectra from thin surface layers differ from that of subsurface layers of the same material. Furthermore, various peak characteristics are studied and a simple and robust method for distinguishing surface from subsurface layers is established, without the need of theoretical modelling. The obtained results are critically important for boosting the sensitivity of nano-FTIR to ultra-thin organic layers and for interpreting nano-FTIR spectra of multilayer samples, particularly to avoid that geometry-induced spectral peak shifts are explained by chemical effects.CICnanoGUNE:nanoscience cooperative research cente

Substrate-enhanced and subsurface infrared near-field spectroscopy of organic layers

112 p.La nano-espectroscopía infrarroja, basada en espectroscopía de transformada de Fourier de campo cercano (nano-FTIR), es una herramienta potente que permite la identificación química de materiales con una resolución espacial nanométrica. Sin embargo, hay muchas preguntas abiertas y desafíos relacionados con la técnica nano-FTIR. Por un lado, detectar una capa molecular de espesor nanométrico depositada sobre un sustrato estándar utilizado en espectroscopía infrarroja (como CaF2) es complicado debido a las débiles señales de nano-FTIR. Por otro lado, la capacidad de la utilización de la técnica nano-FTIR para analizar materiales subsuperficiales es un terreno que ha sido poco explorado. En esta tesis se demuestra, en primer lugar, que hay un aumento significativo en la señal al colocar la capa molecular sobre sustratos altamente reflectantes como el silicio o el oro.Además, se observa que hay un aumento en la señal al explotar el mecanismo de acoplamiento entre la punta y los polaritones del sustrato, y por iluminar la punta con polaritones de superficie. El aumento en la señal es alrededor de dos órdenes de magnitud sobre un sustrato de cuarzo fonón-polaritónico, en comparación a la señal obtenida sobre el sustrato de CaF2. En segundo lugar, se presenta la espectroscopía nano-FTIR de capas orgánicas subsuperficiales, en la que se observa que los espectros nano-FTIR de capas superficiales delgadas difieren de los espectros de las capas subsuperficiales del mismo material orgánico. Asimismo, se estudia la correlación de las diferentes características de los picos obtenidos por nano-FTIR, y se establece una metodología simple y robusta capaz de distinguir capas superficiales de capas subsuperficiales. Los resultados obtenidos son fundamentalmente importantes para impulsar la espectroscopía nano-FTIR hacia la detección rutinaria de monocapas y moléculas individuales y, además, para la interpretación de los espectros nano-FTIR de muestras multicapa, en particular para evitar que los cambios en los picos espectrales inducidos por la geometría se expliquen mediante efectos químicos.-Infrared nanospectroscopy based on Fourier transform infrared near-field spectroscopy (nano-FTIR) is an emerging nanoanalytical tool with large application potential for label-free chemical characterization of organic and inorganic composite surfaces. However, there are many open questions and challenges related to nano-FTIR. On the one hand, the detection of thin organic layers is still challenged by weak nano-FTIR signals, when the organic layer is placed on standard substrates such as CaF2. On the other hand, the potential capability of nano-FTIR for subsurface material analysis is still largely unexplored terrain. In this thesis, it is first demonstrated that a significant enhancement of the nano-FTIR signal from a thin organic layer is obtained by placing the organic layer on highly reflecting substrates such as silicon or gold. An even further signal enhancement is demonstrated by exploiting polariton-resonant tip-substrate coupling and surface polariton illumination of the nano-FTIIR probing tip. A signal enhancement of up to nearly two orders of magnitude is achieved on a polaritonic quartz substrate, as compared to the standard IR substrate CaF2. Secondly, it is demonstrated that nano-FTIR spectroscopy of subsurface organic layers is possible, revealing that nano-FTIR spectra from thin surface layers differ from that of subsurface layers of the same material. Furthermore, various peak characteristics are studied and a simple and robust method for distinguishing surface from subsurface layers is established, without the need of theoretical modelling. The obtained results are critically important for boosting the sensitivity of nano-FTIR to ultra-thin organic layers and for interpreting nano-FTIR spectra of multilayer samples, particularly to avoid that geometry-induced spectral peak shifts are explained by chemical effects.CICnanoGUNE:nanoscience cooperative research cente

Subsurface chemical nanoidentification by nano-FTIR spectroscopy

Nano-FTIR spectroscopy allows chemical characterization of composite surfaces, but its capability in subsurface analysis is not much explored. The authors show that spectra from thin surface layers differ from those of subsurface layers of the same organic material, and establish a method for distinguishing them in experiments

Solvent-structured PEDOT:PSS surfaces: fabrication strategies and nanoscale properties

We present the preparation of nanostructured conducting PEDOT:PSS thin films by solvent vapor annealing (SVA), using the low boiling point solvent tetrahydrofuran (THF). An Atomic Force Microscopy (AFM) study allowed the observation of distinct nanostructure development as a function of solvent exposure time. Moreover, the nanostructures’ physical properties were evaluated by nanomechanical, nanoelectrical, and nano-FTIR measurements. In this way, we were able to differentiate the local response of the developed phases and to identify their chemical nature. The combination of these techniques allowed to demonstrate that exposure to THF is a facile method to effectively and selectively modify the surface nanostructure of PEDOT:PSS, and thereafter its final properties. Moreover, our nanoscale studies provided evidence about the molecular rearrangements that PEDOT:PSS suffers during nanostructure fabrication, a fundamental fact in order to expand the potential applications of this polymer in thermoelectric and optoelectronic devices

A multi-sensor traffic scene dataset with omnidirectional video

The development of vehicles that perceive their environment, in particular those using computer vision, indispensably requires large databases of sensor recordings obtained from real cars driven in realistic traffic situations. These datasets should be time shaped for enabling synchronization of sensor data from different sources. Furthermore, full surround environment perception requires high frame rates of synchronized omnidirectional video data to prevent information loss at any speeds. This paper describes an experimental setup and software environment for recording such synchronized multi-sensor data streams and storing them in a new open source format. The dataset consists of sequences recorded in various environments from a car equipped with an omnidirectional multi-camera, height sensors, an IMU, a velocity sensor, and a GPS. The software environment for reading these data sets will be provided to the public, together with a collection of long multi-sensor and multi-camera data streams stored in the developed format

Solvent-structured PEDOT:PSS surfaces: Fabrication strategies and nanoscale properties

We present the preparation of nanostructured conducting PEDOT:PSS thin films by solvent vapor annealing (SVA), using the low boiling point solvent tetrahydrofuran (THF). An Atomic Force Microscopy (AFM) study allowed the observation of distinct nanostructure development as a function of solvent exposure time. Moreover, the nanostructures’ physical properties were evaluated by nanomechanical, nanoelectrical, and nanoinfrared (nano-FTIR) measurements. In this way, we were able to differentiate the local response of the developed phases and to identify their chemical nature. The combination of these techniques allowed to demonstrate that exposure to THF is a facile method to effectively and selectively modify the surface nanostructure of PEDOT:PSS, and thereafter its final properties. Moreover, our nanoscale studies provided evidence about the molecular rearrangements that PEDOT:PSS suffers during nanostructure fabrication, a fundamental fact in order to expand the potential applications of this polymer in thermoelectric and optoelectronic devices.M. S., A. A. and D. E. M-T, acknowledge funding from the Basque Government (projects codes: IT-1175-19 and IT-1566-22) and the Spanish Ministry of Science and Innovation (MCIU/AEI/FEDER; EU. Code: PID2019-104650GB-C21). R. H. and L. M., acknowledge funding from the Spanish Ministry of Science and Innovation (projects codes: RTI2018-094830-B-100 and MDM-2016-0618 of the Maria de Maeztu Units of Excellence Program) and from the Basque Government (projects codes: IT1164-19).Peer reviewe

Percolating superconductivity in air-stable organic-ion intercalated MoS2

When doped into a certain range of charge carrier concentrations, MoS2 departs from its pristine semiconducting character to become a strongly correlated material characterized by exotic phenomena such as charge density waves or superconductivity. However, the required doping levels are typically achieved using ionic-liquid gating or air-sensitive alkali-ion intercalation, which are not compatible with standard device fabrication processes. Here, the emergence of superconductivity and a charge density wave phase in air-stable organic cation intercalated MoS2 crystals are reported. By selecting two different molecular guests, it is shown that these correlated electronic phases depend dramatically on the intercalated cation, demonstrating the potential of organic ion intercalation to finely tune the properties of 2D materials. Moreover, it is found that a fully developed zero-resistance state is not reached in few-nm-thick flakes, indicating the presence of 3D superconductive paths that are severed by the mechanical exfoliation. This behavior is ascribed to an inhomogeneous charge carrier distribution, which is probed at the nanoscale using scanning near-field optical microscopy. The results establish organic-ion intercalated MoS2 as a platform to study the emergence and modulation of correlated electronic phases.This work was supported by “la Caixa” Foundation (ID 100010434), under the agreement LCF/BQ/PI19/11690017, by the Spanish Ministerio de Ciencia e Innovación under Projects PID2019-108153GA-I00, PID2021-128004NB-C21, PID2021-123949OB-I00, PID2021-122511OB-I00. This work was also supported by the FLAG-ERA grant MULTISPIN, by the Spanish MCIN/AEI with grant number PCI2021-122038-2A. B.M.-G. thanks Gipuzkoa Council (Spain) in the frame of the Gipuzkoa Fellows Program. This work was supported by CEX2020-001038-M/AEI/10.13039/501100011033 under the Maria de Maeztu Units of Excellence Program. I.N. acknowledges financial support by the German Research Foundation (DFG) under project no. 467576442. The authors also thank SGIker Medidas Magneticas Gipuzkoa (UPV/EHU/ERDF, EU) for the technical and human support.Peer reviewe

The Medicago truncatula reference accession A17 has an aberrant chromosomal configuration

• Medicago truncatula (barrel medic) has emerged as a model legume and accession A17 is the reference genotype selected for the sequencing of the genome. In the present study we compare the A17 chromosomal configuration with that of other accessions by examining pollen viability and genetic maps of intraspecific hybrids. • Hybrids derived from crosses between M. truncatula accessions, representative of the large genetic variation within the germplasm collection, were evaluated for pollen viability using Alexander's stain. Genetic maps were generated for the following crosses: SA27063 × SA3054 (n = 94), SA27063 × A17 (n = 92), A17 × Borung (n = 99) and A17 × A20 (n = 69). • All F 1 individuals derived from crosses involving A17 showed 50% pollen viability or less. Examination of the recombination frequencies between markers of chromosomes 4 and 8 revealed an apparent genetic linkage between the lower arms of these chromosomes in genetic maps derived from A17. • Semisterility and unexpected linkage relationship are both good indicators of a reciprocal translocation. The implications of the A17 distinctive chromosomal rearrangement on studies of genetic mapping, genome sequencing and synteny between species are discussed