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Tesi en modalitat de compendi de publicacions. Aplicat embargament des de la data de defensa fins el 7/1/2022, This work develops a novel capacitor device based on the use of nanotechnology. The device starts from the exiting metal-insulator-metal (MIM) concept, but instead of a continuous insulator layer, dielectric nanoparticles are used. Nanoparticles are mainly of silicon oxide (silica) and polystyrene (PS) and the diameter values are 255nm and 295nm respectively. The nanoparticles contribute to a very high surface to volume ratio and are easily available at low cost. The deposition technique developed in this work is the electrospray, which is a bottom-up fabrication technology that allows batch processing and achieves a good compromise between large area and low deposition time. With the objective of increasing the deposit surface, the electrospray set-up has been tuned to allow deposition areas from 1cm2 to 25cm2. The fabricated devices, the so called nanoparticles metal insulator metal (NP-MIM) capacitors, offer higher capacitance values than a similar conventional capacitor with a continuous insulator layer. In the case of silica NP-MIMs, a factor as high as 1000 of capacitance enhancement is achieved, whereas polystyrene NP-MIMs has capacitance gain of 11. In addition, silica NP-MIMs show capacitive behaviours in a certain frequency range which depends on the humidity and thickness of the nanoparticles layer, while polystyrene MIMs always maintain their capacitive behaviour. The fabricated devices have been characterized by scanning electron microscopy (SEM) measurements complemented with focusing ion beam (FIB) drilling to characterise the topography of the NP-MIMs. The devices have also been characterized by impedance spectroscopy measurements, at different temperatures and humidifies. The origin of the enhanced capacitance is associated in part to humidity in the nanoparticles interfaces. A circuital model based on distributed elements has been developed to fit and predict the electrical behaviour of the NP-MIMs. In summary, this thesis shows the design, fabrica, Este trabajo desarrolla un novedoso dispositivo condensador basado en el uso de la nanotecnología. El dispositivo parte del concepto existente de metal-aislador-metal (MIM), pero en lugar de una capa aislante continua, se utilizan nanopartículas dieléctricas. Las nanopartículas son principalmente de óxido de silicio (sílice) y poliestireno (PS) y los valores de diámetro son 255nm y 295nm respectivamente. Las nanopartículas contribuyen a una alta relación superficie/volumen y están fácilmente disponibles a bajo costo. La técnica de depósito desarrollada en este trabajo es el electrospray, que es una tecnología de fabricación ascendente (bottom-up) que permite el procesamiento por lotes y logra un buen compromiso entre una gran superficie y un bajo tiempo de depósito. Con el objetivo de aumentar la superficie de depósito, la configuración de electrospray ha sido ajustada para permitir áreas de depósito de 1cm2 a 25cm2. El dispositivo fabricado, los llamados condensadores de metal aislante de nanopartículas (NP-MIM) ofrecen valores de capacitancia más altos que un condensador convencional similar con una capa aislante continua. En el caso de los NP-MIM de sílice, se alcanza un factor de hasta 1000 de mejora de la capacidad, mientras que los NP-MIM de poliestireno tienen una ganancia de capacidad de 11. Además, los NP-MIM de sílice muestran comportamientos capacitivos en un cierto rango de frecuencias que depende de la humedad y el grosor de la capa de nanopartículas, mientras que los MIM de poliestireno siempre mantienen su comportamiento capacitivo. Los dispositivos fabricados se han caracterizado por mediciones de microscopía electrónica de barrido (SEM) complementadas con perforaciones de haz de iones de enfoque (FIB) para caracterizar la topografía de los NP-MIMs. Los dispositivos también se han caracterizado por mediciones de espectroscopia de impedancia, a diferentes temperaturas y humedades. El origen de la capacitancia aumentada está asociado en parte a la hume, Postprint (published version)

© <2020>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, The objective of this paper is to present a charge trapping control method for MIM capacitors in whichthe dielectric is made of electrospray-deposited silica nanoparticles. The influence of the bias voltage onthe impedance spectra of the devices is analyzed, as well as the main conduction mechanisms along thestructure. The control method allows to monitor and control the long term drifts in the impedance ofthese devices, which are a result of the applied bias voltages., This work was supported by the Spanish Ministry MINECO un-der project RTI2018-098728-B-C33, by the European Space Agencyunder project ESA AO/1e8876/17/NL/CRS and by SENESCYT of therepublic of Ecuador under agreement 2016-AR5G8871, Peer Reviewed, Postprint (author's final draft)

© <2020> Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, Impedance spectroscopy differences between colloidal 295-nm silica and 300-nm polystyrene nanoparticles in deionized water are analyzed in this work. Using two different two-electrode measurement setups, designed for this application, impedance spectroscopy measurements performed directly in the colloidal suspensions with same nanoparticles size, shape and concentration, are fitted using Randles circuit models. The parameter analysis allows to identify the suspension response, the electrode-suspension interfaces response and nanoparticle double layer response. The first measurement system consists of a two aluminum wire electrodes characterized in a frequency range from 0.1Hz to 100 kHz while the second system was two square stainless steel electrodes characterized from 0.1Hz to 5 MHz. According to the results, polystyrene nanoparticles suspension presents higher conductivity and higher values of capacitance than silica suspension. It is revealed that as the nanoparticle concentration decreases, the suspension conductivity decreases for both colloidal suspensions. On the other hand, the electrode polarization effect contributed with high impedance and capacitance values, but showed a contrary behavior with the variation of the nanoparticles concentration. These differences found mainly arise because of the hydrophilic and hydrophobic nature of the silica and polystyrene nanoparticle surfaces., Peer Reviewed, Postprint (author's final draft)

In this study, a metal-insulator-metal capacitor structure is fabricated using polystyrene nanoparticles. Impedance spectroscopy is used to evaluate the performance of this capacitor in which we found a significant magnitude increment in capacitance and loss tangent compared with an equivalent ideal capacitor with continuous polystyrene layer and same geometry. Capacitance values up to 11.7 and loss tangent values up to 387 (at 0.1 Hz) larger than the expected for a continuous polystyrene MIM capacitor are achieved. The capacitor shows a good stable capacitive behaviour in the frequency range from 0.1 Hz to 100 kHz at room temperature, 30 °C, 40 °C and 50 °C without an effective relaxation process. Nyquist, capacitance, loss tangent and normalized powers curves are analysed by modified Randles model. Also, a slight decrease in the capacitance value at 50 °C is observed, which that may be attributed to space charge localized at the nanoparticles interface and that are affected by the temperature changes., Peer Reviewed, Postprint (author's final draft)

© <2018> Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, Mass production of ordered nanostructures with enhanced optical properties such as colloidal crystals for applications such as solar cells or organic light emitted diodes demands low-cost and large-scale manufacturing techniques. In order to enlarge the deposition area of colloidal crystals, this paper presents the results of two different approaches that use the electrospray technique. Areas as large as 25¿cm2 have been achieved by using an array of needles, whereas up to 7.5¿cm2 areas were achieved by using an additional focusing electrode placed on the same plane as the needle nozzle. COMSOL simulations have been used as a guide for the set up design. The ordered deposition of the nanoparticles has been assessed by reflectance measurements and SEM/FIB observations., Peer Reviewed, Postprint (author's final draft)

Electrospray is used for a device that employs electricity to disperse a liquid or for the fine aerosol resulting from this process. Our group has recently developed a novel way of electrospraying 3D ordered nanostructures (figure 1) (patent number P201131081). Applications in colloidal crystals and photovoltaics have been already tested, but there is a wide range of applications in fabricating novel electronic devices, like the nano-based ultracapacitors, nano-MOSFETs and other surface patterned devices. In this work a supercacacitor device based on the deposition of nanop, Realization/ Investigation of a novel interdigitated capacitor and its efficiency from a nanoparticle deposit (SiO2) and/or an electrolytic gel model., Realización/ Investigación de un nuevo modelo de condensador interdigitado y su eficiencia a partir de un depósito de nanopartículas (SiO2) y/o un modelo de gel electrolítico., Realització/Investigació d'un nou model de condensador interdigital juntament amb el rendiment d'aquest amb un depòsit de nanopartícules (Si02) i/o un model de gel electrolític.

In this study, we have fabricated metal-insulator-metal (MIM) capacitors where the insulator layer is made of 255¿nm diameter silica nanospheres. The MIM devices have been characterized and modeled by electrochemical impedance spectroscopy (EIS) and charge-discharge transients. Fitting the results with modified Randles models agreed well with three constant phase elements, three leakage resistors, and a Warburg element. According to the results of the fitting of the charge-discharge measurements and of the modified Randles model, values of real capacitances up to thousand times larger than the theoretical capacitance of a similar capacitor with a continuous layer dielectric are found. These unexpected high capacitances seemed to be related to the ability of the nanospheres to trap electric charges due to surface hydroxyl groups that are originated by the adsorption of water molecules, thereby indicating that the environmental humidity plays a role. This has been ascertained by measurements at several temperatures above the ambient and the resulting capacitance decreases as temperatures increases. Furthermore, active and reactive parts of the complex power have been measured showing capacitive or resistive behavior depending on the frequency. These results suggest that this novel MIM device based on nanospheres may be a new baseline technology for supercapacitor technology., Peer Reviewed, Postprint (author's final draft)

The Electrospray technique allows the formation of small droplets from aqueous solutions that may contain nanoparticles of different materials in suspension, leading to the deposition of layers of the nanoparticles. The geometry of the nozzle and the electric field lines from the tip to substrate are key parameters to concentrate the jet of nanodroplets to enhance the deposition control. This work examines the introduction and effect of a guard ring placed at a specific distance from the nozzle. We have been able to make observations with a CCD camera of the fast formation of the Taylor cone with a long elongated jet of deionized water when both the guard ring and substrate are connected to ground. Main results show that the guard ring allows to concentrate the spray jet, reduces the voltage required to shape the cone and reduce the dispersion of the deposit., Peer Reviewed, Postprint (published version)

An electrospray technique has been used to deposit SiO2 nanoparticles as insulator layer of a metal-insulator-metal device. Impedance spectroscopy measurements show that a 4.4 factor increase in capacitance is achieved compared to a continuous dielectric layer of the same permittivity and dimensions., Peer Reviewed, Postprint (published version)

Anglès: Nowadays there is an interesting grown of the manipulation of matter at the nanometric scale in order to develop new Nano-devices and to make use of theirs nanometric properties. The research group of Micro and Nano Technologies (MNT) of UPC has developed a technique for depositing Nano-particles, called electrospray, is being applied to the manufacture of Nanophotonic devices. In this project the electrospray technique is used to deposit Nano-particles of dielectric materials and manufacture a Metal- Insulator -Metal (MIM) device. The capacitors fabricated in this project, consist of a metal layer deposited by sputtering, a layer of Nano-particles of insulating material deposited by electrospray and another metal layer deposited by thermal evaporation. The matter used for Nano-particles is silicon oxide nanospheres, the metal is aluminum. Work areas will be of the order of 7x10-6 m2 and thicknesses of the order of 10 microns. By electron microscope (SEM -FIB) of the CRNE lab, pictures are taken once manufactured devices. Measures are made on function of frequency of capacity, equivalent series resistance, impedance, phase; the Nyquist plot is also obtained to analyze the behavior of the MIM devices and contrast with some capacitors in the literature. The results indicated capacitance density of 0.2mF/cm2 to 1kHz and 0V dc bias. This project aims to analyze the interesting features arising from the use of nano-spheres for the performance of the insulation. Preliminary evidence suggests that the effect of using these nanospheres causes an increase of several orders of magnitude expected capacity, suggesting that these new devices are promising for use as "supercapacitors"., Castellà: Actualmente existe un gran auge por el interés de la manipulación de la materia a escala nanométrica con la intención de desarrollar nuevos nano-dispositivos y aprovechar las propiedades nanométricas del material. El grupo de investigación de Micro y Nano Tecnologías (MNT) de la UPC ha desarrollado recientemente una técnica para depositar nano-partículas, llamada Electrospray, se está aplicando a la fabricación de dispositivos Nanofotónicos. En este proyecto se utiliza la técnica Electrospray para depositar nano-partículas de materiales dieléctricos y fabricar un nuevo dispositivo Metal-Aislante-Metal (MIM). Los condensadores fabricados en este proyecto, constarán de una capa de metal depositada por Pulverización Catódica, una capa de nano-partículas de material aislante depositada por Electrospray y otra capa de metal depositada por Evaporación térmica. El material usado para las nano-partículas es óxido de silicio (del orden de 250nm), el metal es aluminio. Las áreas de trabajo serán del orden de 7x10-6 m2 y los espesores del orden de 10 micrómetros. Mediante el microscopio electrónico (SEM-FIB) del laboratorio de CRNE se han tomado imágenes una vez fabricado los dispositivos. Se han realizado medidas en función de frecuencia de capacidad, resistencia serie equivalente, impedancia, fase; también ha obtenido el diagrama de Nyquist para analizar el comportamiento del MIM y contrastar los dispositivos con algunos existentes en la literatura. Los resultados indicaron densidad capacitiva de 0.2mF/cm2 a frecuencias de 1kHz y 0V de polarización. En este proyecto se pretende analizar las interesantes características que se derivan de la utilización de nano-esferas para la realización del aislante. Pruebas preliminares sugieren que el efecto de utilizar estas nano-esferas provoca un aumento de varios órdenes de magnitud la capacidad esperada, sugiriendo que estos nuevos dispositivos son prometedores en su utilización como “supercondensadores”., Català:Actualment hi ha un gran auge per l'interès de la manipulació de la matèria a escala nanomètrica amb la intenció de desenvolupar nous nano- dispositius i aprofitant les propietats nanomètriques del material. El grup de recerca de Micro i Nano Tecnologies ( MNT ) de la UPC ha desenvolupat recentment una tècnica per dipositar nano - partícules, anomenada Electrospray, s'està aplicant a la fabricació de dispositius nanofotònics. En aquest projecte s'utilitza la tècnica Electrospray per dipositar nano-partícules de materials dielèctrics i fabricar un nou dispositiu Metall-Aïllant-Metall ( MIM ) . Els condensadors fabricats en aquest projecte, constaran d'una capa de metall dipositada per Polvorització catòdica, una capa de nano-partícules de material aïllant dipositada per Electrospray i una altra capa de metall dipositada per Evaporació tèrmica. El material usat per a les nano- partícules és òxid de silici, el metall és alumini. Les àrees de treball seran de l'ordre de 7x10 -6 m2 i els gruixos de l'ordre de 10 micròmetres. Mitjançant el microscopi electrònic ( SEM - FIB ) del laboratori de CRNE s'han pres imatges un cop fabricat els dispositius. S'han realitzat mesures en funció de freqüència de capacitat, resistència sèrie equivalent, impedància, fase, també ha obtingut el diagrama de Nyquist per analitzar el comportament del MIM i contrastar els dispositius amb alguns existents a la literatura. Els resultats van indicar densitat capacitiva de 0.2mF/cm2 a freqüències de 1kHz i 0V de polarització. En aquest projecte es pretén analitzar les interessants característiques que es deriven de la utilització de nano-esferes per a la realització de l'aïllant. Proves preliminars suggereixen que l'efecte d'utilitzar aquestes nano- esferes provoca un augment de diversos ordres de magnitud la capacitat esperada, suggerint que aquests nous dispositius són prometedors en la seva utilització com "supercondensadores".