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Seminarios y Eventos

Seminars and Events

Tesis Doctorales


26 July 2021, 17:00 h. Saln de Actos

Novel Developments and Applications of
Bimodal Atomic Force Microscopy and 3D-AFM

Simone Benaglia
ForceTool group


Supervisor(s): Ricardo Garcia

Understanding surface and interfacial properties of materials is fundamental to employ them for novel applications. The Atomic Force Microscope is one of the most versatile tools for that purpose. Among the different AFM techniques developed so far, dynamic modes stand out for their flexibility. Dynamic AFM methods consist of an oscillatory excitation of the AFM cantilever [1]. Recently, novel advanced dynamic AFM techniques have been developed with three general purposes: (i) higher sensitivity, (ii) faster acquisition time, (iii) ability to analyse material properties not accessible before. In particular, bimodal AFM and 3D-AFM are the advanced dynamic methods of interest. Bimodal AFM is a multifrequency AFM technique based on the simultaneous excitation of two eigeinmodes of the AFM cantilever. Here, it is shown how it can be applied to unravel different types of elastic and viscoelastic properties of soft matters at the nanoscale. The reliability of the technique was verified on test samples; then, bimodal AFM was applied to understand the mechanical behaviour of organic electronic materials. 3D-AFM is a volume AFM technique that allows to obtain an atomic resolution of a three-dimensional space. In particular, it can be used to visualize the solid-liquid interface (SLIs) of a variety of liquids on surfaces of different nature with sub-nm resolution. 3D-AFM was employed to map the particular behaviour that hydrophobic layered materials have in contact with water. Moreover, the technique was used to visualise the SLI of highly concentrated solutions in contact with charged surfaces




20 July 2021, 10:30 h. online

ENHANCING THE PERFORMANCE OF CARBON/CARBON SUPERCAPACITORS VIA AQUEOUS SOLVENT-IN-SALT ELECTROLYTES

Xuejun Lu
Bioinspired Materials Group


Supervisor(s): Prof. Francisco del Monte & Dra. Mara Concepcin Gutirrez

This Thesis is devoted to study various combinations of new aqueous electrolytes not only in terms of selection and synthesis of salts and solvents but also interaction mechanisms. The so-called aqueous eutectic-in-salt (AEIS), bi-solvent in zwitterionic-based protic ionic liquids (BS-in-ZPIL) and tri-solvent-in-salt (TSIS) have been exhaustively studied and efforts have been taken to demonstrate the formation and evolution of the different concentrated solvation species and electrochemically active hydrogen bond complex structures following by techniques (such as Raman and NMR spectroscopies, and MD simulations) with the aim of developing low cost and excellently functional electrolytes,. Ultimately, this essay is dedicated to present the high attractiveness of designing new and low-cost aqueous electrolytes that offered an improved performance.

Link




14 July 2021, 12:00 h. Saln de Actos

Caracterizacin fsica y lser de monocristales de granates desordenados tipo Ca3(NbGa)5012 dopados con Yb+3

Jorge Omar lvarez Prez


Supervisor(s): Carlos Zaldo

Se aborda un estudio detallado de las propiedades fsicas de los granates de Calcio-Niobio-Galio (CNGG) y de las propiedades espectroscpicas y lser del Yb3+ en este tipo de monocristales que, mediante el empleo de una metodologa diferente a la encontrada en la literatura, puede ayudar a optimizar el rendimiento lser




07 July 2021, 11:00 h. Saln de Actos

Orbital Selective Spin-Fluctuations physics in iron-based superconductors

Raquel Fernndez Martn
Universidad Autnoma de Madrid (UAM)


Supervisor(s): Beln Valenzuela Requena y Laura Fanfarillo

There is no temperature below absolute zero. Researchers have tried to reach this lower limit and this has led to the discovery of new physical phenomena, e.g. superconductivity, which understanding is still unknown. Since its discovery, hundreds of new superconductors have been found. In this Thesis we focus on the family of iron-based superconductors (IBS). Although the crystallographic and electronic structures are very similar in these materials, they present a very different phenomenology. The development of a theory that can explain the complex phenomenology of IBS within a common framework is one of the most important theoretical challenges in the field.

This Thesis shows how the diverse phenomenology of various families of IBS can be understood within a common framework: the Orbital Selective Spin Fluctuations scenario. Thanks to the orbital selectivity of the magnetic excitations of the system, a spin-orbital interplay arises in the magnetic susceptibility, superconducting gaps and velocity and the scattering rate in the nematic phase of IBS. This model has been extensively used to study the phenomenology of FeSe and 122 systems. The generalization to a five-pockets model, also performed in this Thesis, put the basis to exploit this model to analyze more IBS compounds.

Beyond IBS, orbital selectivity might also appear in other compounds in which the multiorbital character has a significant role to play. Without doubt, there are numerous avenues where orbital selectivity may play an important role, leaving many possibilities to be explored.




29 April 2021, 11:00 h.

Estudio del efecto del desorden en las propiedades fotnicas de materiales autoensamblados.

Jose ngel Pariente
ICMM-CSIC


Supervisor(s): Ceferino Lpez
lvaro Blanco

Enlace
Cdigo de acceso: 168538

Esta tesis doctoral trata sobre la explotacin de las propiedades fotnicas de sistemas autoensamblados con el fin de caracterizar dos fenmenos fsicos fundamentales: las transiciones de fase y la introduccin de desorden en materiales nanoestructurados.




23 April 2021, 11:00 h. Sala de Seminarios, 182

Dinmica resuelta en tiempo de una nica pared de dominio y procesos de imanacin en microhilos magnticos

Esther Calle Ramrez
Instituto de Magnetismo Aplicado Salvador Velayos


Supervisor(s): Rafael Prez del Real
Manuel Vzquez Villalabeitia

El control del desplazamiento de paredes de dominio a lo largo de nanoestructuras magnticas es un tema que ha cobrado inters en los ltimos aos por su importancia para el desarrollo de nuevos dispositivos espintrnicos y memorias, en los cuales la velocidad de operacin est determinada por la velocidad de propagacin de estas paredes.
Los microhilos magnticos estudiados en esta tesis son materiales amorfos que poseen una estructura muy particular de dominios, relacionada con la elevada anisotropa magnetoelstica que se induce durante su proceso de fabricacin y que hace posible el estudio de la dinmica de propagacin de una nica pared.
Esta tesis se ha centrado en el estudio y control de la dinmica resuelta en tiempo de la pared de dominio en microhilos altamente magnetostrictivos. Usando el efecto Mateucci intrnseco que presentan microhilos amorfos de magnetostriccin positiva, se ha desarrollado un mtodo de medida de la velocidad de la pared con resolucin temporal que ha permitido identificar los procesos de nucleacin, aceleracin y propagacin de la pared bajo la aplicacin de un campo constante. Asimismo, se ha inducido el frenado local de la pared de dominio y estudiado el movimiento de paredes inyectadas en el microhilo bajo la aplicacin combinada de un campo de propagacin uniforme y un campo local no homogneo, obteniendo que para campos mnimos del orden del campo de friccin se produce un atrapamiento estocstico de la pared que ha sido atribuido al carcter dinmico del campo de friccin. El estudio del movimiento alterno de la pared ha puesto de manifiesto la importancia de su inercia, determinando la existencia de un rango de frecuencias crtico por encima del cual la pared oscila sin llegar a detenerse, como cabra esperar por efecto de la friccin. Por ltimo, se ha puesto de manifiesto la capacidad de emplear una corriente elctrica aplicada al microhilo para inducir y controlar el movimiento de la pared de dominio, a partir de la interaccin entre el campo Oersted generado por la corriente en el interior del hilo y la componente azimutal de la imanacin.





22 April 2021, 11:00 h. online

Studies on secondary electron emission induced charging in dielectric materials: Novel methods and applications for space and plasma technologies

Leandro Olano Garca
Universidad Autnoma de Madrid


Supervisor(s): Isabel Montero y Mara Eugenia Dvila

Link




26 March 2021, 11:00 h. Saln de Actos

Fenomenos de orden-desorden en oxidos con estructura tpo rutilo y su aplicacin como soportes en catalizadores heterogneos

Jon Canca Ruiz
Universidad Autnoma de Madrid


Supervisor(s): Fernando Agull Rueda y Jorge Hernndez






17 December 2020, 11:00 h. online

Design and development of biomaterials for spinal cord injury repair (Diseo y desarrollo de biomateriales para la reparacin de la mdula espinal lesionada)

Ana Domnguez Bajo
Instituto de Ciencia de Materiales de Madrid, CSIC


Supervisor(s): Dra. M. Concepcin Serrano Lpez-Terradas y Dra. Elisa Lpez Dolado

Actualmente no existe ningn tratamiento eficaz para la lesin medular, caracterizada principalmente por el dao de los axones neuronales y la creacin de un entorno inhibitorio para la regeneracin. En esta tesis, hemos investigado dos plataformas diferentes capaces de actuar como interfaces neurales. Por un lado, hemos estudiado la biocompatibilidad in vitro de nanohilos metlicos que funcionarn como nanoelectrodos dentro de un dispositivo capaz de actuar como bypass en la lesin. Estos nanohilos metlicos se han fabricado por electrodeposicin de nquel (Ni) u oro (Au) sobre una base plana y flexible de Au, dispuestos verticalmente sobre ella. Por otro lado, dos tipos de plataformas 3D fabricadas a partir de xido de grafeno reducido se han implantado crnicamente en un modelo de hemiseccin de la mdula espinal cervical en rata. Los implantes han consistido en una espuma altamente porosa y microfibras integradas en un hidrogel de gelatina. Con respecto a los electrodos metlicos, la composicin qumica y la nanotopografa modulan el comportamiento de las clulas neurales in vitro. Con respecto a los biomateriales de grafeno, ambos implantes han promovido la estabilizacin del tejido espinal lesionado, as como la presencia de estructuras neuronales acompaadas de vasos sanguneos en la lesin. Adems, las espumas de grafeno reducen el dao perilesional y no causan efectos adversos por compresin ni traccin. En conclusin, estos resultados demuestran el potencial de estas plataformas como interfaces neurales para la reparacin de la mdula espinal lesionada.




11 December 2020, 10:00 h. online

Straintronic photodetectors based on 2D materials

Patricia Gant Pinar
Universidad Autnoma Madrid


Supervisor(s): Andrs Castellanos Gmez and Riccardo Frisenda

Since the first fabrication of a transistor in 1947, electronics is been improving its performance by adding more elements to the electronic devices. In order to maintain the level of improvement, the size of their components decreased, which have led to difficulties during the last years. Some strategies to continue the enhancement of electronics can be the study of new materials like 2D semiconductors or including more tuning knobs in the components to increase the functionality of each component. The different options for increasing the responses of the components include the control of different properties (degrees of freedom) of the device through control the valey or spin polarization or applying external deformations leading to valleytronics, spintronics, straintronics respectively.
This thesis develops a proof-of-concept straintronic device, which would proof the viability of this technique to keep the electronic progress. Thus, this device is fabricated with a new semiconductor, which allows us to fabricate this type of device unlike silicon (Si). This new material is a 2D semiconductor from the transition metal dichalcogenides (TMDCs) family, MoS2. Due to the special characteristics of 2D materials, the techniques used for studying and manipulating them are different from the common methods used in 3D semiconductor industry.
We fabricate several MoS2 simple photodetector devices which can be strained. These photodetectors show an optoelectrical response to the strain.
The new design will allow to have components with higher functionalities and the use of 2D materials solve some of the issues lately found in the electronics industry.




04 December 2020, 16:00 h. Saln de Actos

Two-dimensional III-VIA semiconductors and their applications in optoelectronic devices

Qinghua Zhao
Universidad Autnoma Madrid


Supervisor(s): Andrs Castellanos-Gmez y Riccardo Frisenda

Two-dimensional (2D) semiconductors, initialed by the isolation of graphene in 2004, have drawn a great research interest thanks to their remarkable mechanical, electrical, optical, and optoelectronic properties. Their layered structure, originating from the strong in-plane covalent bonds and weak out-of-plane van der Waals interactions, allows such materials being stable with atomically thin geometry. Thanks to the ultrathin nature and dangling-bond-free surface, various advanced heterostructures-based devices with superior performance have been demonstrated without being hampered by their lattice mismatch, which make them as promising candidates for future nano-electronic and optoelectronic applications. As novel 2D members from III VIA semiconducting group, Gallium selenide (GaSe) and Indium selenide (InSe), are barely explored but recently both reach exciting promise in theory achievements and application research. Thanks to their unique electron band structures and strong light-matter interactions, they both are sensitive to external stimuli, which can be advantageous for certain applications but also brings drawbacks for others, thus motivates the goal of this thesis that exploring how the environment, light and strain play roles on the properties of these materials.
This thesis demonstrates the great promise of 2D III-VIA semiconducting materials, especially GaSe and InSe, for future electrical and optoelectronic applications. These results, on the one hand, reveal the important role of traps induced by defects in tailoring the properties of devices based on 2D materials, on the other hand, show the reliability of electronic and optoelectronic properties of van der Waals Schottky contacts, which are both attractive for different applications, such as strain engineering and flexible electronics.




01 December 2020, 11:00 h. Online

Sntesis y Procesado Avanzados de los Nuevos Sistemas Y1-xBixMnO3 y Y1-xBixMn1-xFexO3 Diseados para Presentar Multiferroicidad:Estudio Estructural, Propiedades ferroicas

Jose ngel Quintana Cilleruelo

Universidad Internacional Menndez Pelayo


Supervisor(s): Prof. Dra. Mara Alicia Castro Lozano & Dr. Miguel Alguer Gimnez

La memoria de esta Tesis Doctoral presenta el trabajo de investigacin que describe por primera vez la sntesis de dos sistemas binarios completos con frmulas generales Y1-xBixMn1-xFexO3 (YMnO3 BiFeO3; YMBF) y Y1-xBixMnO3 (YMnO3 BiMnO3; YMBM) por un mtodo mecanoqumico, as como su optimizacin utilizando dos molinos planetarios de distintas caractersticas. Tambin se presenta la caracterizacin estructural de ambos sistemas, el estudio de sus propiedades magnticas y el procesado de materiales cermicos densos pertenecientes al sistema YMBF junto con su caracterizacin elctrica.




30 October 2020, 11:00 h. Online

Reactividad qumica del para-aminofenol en superficies metlicas. Nuevos mecanismos de sntesis sobre superficies

Nerea Ruiz del Arbol Lasagabaster
Universidad Autonoma de Madrid


Supervisor(s): Jose Angel Martn Gago y Paqui Lpez Fagndez






     

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