La fotónica de silicio es actualmente la tecnología mejor posicionada para reemplazar las conexiones electrónicas tanto dentro de los mismos chips, como entre ellos mismos, con el fin de mejorar su rendimiento. Las principales ventajas de la tecnología fotónica de silicio residen en su bajo coste y en su compatibilidad con las actuales técnicas de fabricación desarrolladas por la industria microelectrónica. Dicha compatibilidad permitiría fabricar tanto chips ópticos como chips híbridos que incluyan componentes ópticos y electrónicos. Los moduladores y los conmutadores optoelectrónicos resultan dispositivos fundamentales en aplicaciones de telecomunicaciones. Las principales funciones de los conmutadores y moduladores optoelectrónicos son el enrutamiento y la transmisión de datos de alta velocidad. Esta tesis aborda el diseño y la optimización de la parte eléctrica y óptica (en menor medida) con el fin de optimizar el rendimiento de tales dispositivos desde el punto de vista optoelectrónico. Además, también se tratará la introducción de nuevos materiales compatibles con el silicio y sus procesos de fabricación, como el dióxido de vanadio o el titanato de bario con el fin de demostrar sus propiedades y aplicarlas a los dispositivos optoelectrónicos con el fin de mejorar su rendimiento. / Silicon photonics is nowadays the most promising technology to replace electrical inter- and intra-connections of the chips, increasing the performance in this way. The main advantages of silicon photonics technology lie on its low cost and its compatibility with the fabrications processes of microelectronics industry developed during years which allows the mass production of silicon photonics chips as well hybrid electronic and photonic devices in the same chip. Optoelectronics switches and modulators are key building blocks in photonic devices for tele/datacom applications. Such switches and modulators are devices which provides routing functionalities and the transmission of high speed data respectively. The work of this thesis delves with the design and optimization of silicon based switches and modulators spotlighting the electrical elements. Additionally, the work of this theses deals with the introduction of new silicon-compatible materials as vanadium dioxide and barium titanate, with the aim of demonstrating its functionalities and develop high-performance optoelectronic devices. / La fotònica de silici és actualment la tecnologia millor posicionada per a reemplaçar les connexions electròniques tant dins del propis xips, com entre ells mateixos, amb la finalitat de millorar el seu rendiment. Els principals avantatges de la tecnologia fotònica de silici resideixen en el seu baix cost i en la seua compatibilitat amb les actuals tècniques de fabricació desenvolupades per la indústria microelectrònica. Aquesta compatibilitat permetria fabricar tant xips òptics com a xips híbrids que incloguen components òptics i electrònics. Els moduladors i els commutadors optoelectrònics resulten dispositius fonamentals en aplicacions de telecomunicacions. Les principals funcions dels commutadors i moduladors optoelectrònics són l'encaminament i la transmissió de dades d'alta velocitat. Aquesta tesi aborda el disseny i l'optimització de la part elèctrica i òptica (en menor mesura) amb la finalitat d'optimitzar el rendiment de tals dispositius des del punt de vista optoelectrònic. A més, també es tractarà la introducció de nous materials compatibles amb el silici i els seus processos de fabricació, com el diòxid de vanadi o el titanato de bari amb la finalitat de demostrar les seues propietats i aplicar-les als dispositius optoelectrònics amb la finalitat de millorar el seu rendiment. / Rosa Escutia, Á. (2018). High-efficient electrodes for novel optoelectronic devices in silicon photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/110364 / TESIS

<p>U poslednjih nekoliko decenija, feroelektrici su prepoznati kao dobri kandidati<br />za &scaron;irok spektar primene. Barijum titanat je jedan od najče&scaron;će istraživanih<br />perovskitnih materijala usled tipičnog feroelektričnog pona&scaron;anja na sobnoj<br />temperaturi, sa histerezisnom zavisnosti između polarizacije i električnog polja.<br />Specifična svojstva BaTiO₃ čine ovaj materijal veoma korisnim u proizvodnji<br />kondenzatora, memorija, senzora i dr. Pored toga, paraelektrična faza BaTiO₃<br />ima primenu u proizvodnji mikrotalasnih tunabilnih uređaja. BaTiO₃ pokazuje<br />paralaketrično pona&scaron;anje iznad Kirijeve temperature (120&deg;C) i veliki je izazov<br />modifikovati materijal da bude paraelektričan na sobnoj temperaturi. Delimičnom<br />supstitucijom Ba²⁺ ili Ti⁴⁺ jona, jonima Sr²⁺ ili Zr⁴⁺, respektivno, snižava<br />se Kirijeva temperatura i dolazi do pomeranja fazne transformacije feroelektri<br />čno/paraelektrično na niže temperature. Monolitna keramika na bazi bazi<br />BaTiO₃ je često istraživana kako bi se ispitale promene u strukturi i svojstvima<br />uzrokovane dodatkom dopanata, međutim ne postoji praktična primena ovih<br />materijala u mikrotalasnim tunabilnim tehnologijama. S druge strane, u trendu<br />sveop&scaron;te minijaturizacije elektronskih komponenti, tanki filmovi su prepoznati<br />kao dobri kandidati za proizvodnju tunabilnih uređaja. Jedan od ciljeva ovog<br />istraživanja bio je ispitivanje strukturnih i funkcinalnih svojstava tankih filmova na<br />bazi barijum titanata, BaTiO₃, Ba_1-xSr_xTiO₃ (x=0,1, 0,2, 0,3 i 0,4) i BaTi_1-xZr_xO₃<br />(x=0,1 i 0,2), pripremljenih hemijskom depozicijom iz tečne faze. Metalne<br />soli BaCO₃, C₄H₆O₄Sr i ZrOCl₂ H₂O i Ti(OCH₂CH₂CH₂CH₃)₄ rastvorene su<br />odvojeno u kiseloj sredini i pome&scaron;ane u transparentne solove. Inkdžet &scaron;tampa<br />i spin tehnika kor&scaron;ćene su za depoziciju funkcionalnih filmova na bazi BaTiO₃.<br />Nakon deponovanja, pripremljeni filmovi su termički tretirani na različitim<br />temperaturama do 1000&deg;C. U zavisnosti od koncentracije pripremljeni su filmovi<br />debljine od 100 do 700 nm,sa veličinom zrna od nekoliko desetina nanometara. Strukturna karakterizacija potvrdila je promene u strukturi BaTiO₃ tankih filmova<br />sa dodatkom Sr²⁺ i Zr⁴⁺. Tetragonalna (feroelektrična) faza BaTiO₃ je potvrđena<br />rentgenostrukturnom analizom i Ramanovom spektroskopijom. S druge strane,<br />smanjenje tetragonalnosti je primećeno kod dopiranih uzoraka. Promene u<br />funkcionalnosti dopiranih BaTiO₃ filmova analizirane su na osnovu dielektričnih<br />i feroelektričnih merenja. Izvr&scaron;ene analize su potvrdile feroelektrično pona&scaron;anje<br />kod BaTiO₃, dok se feroelektrični odgovor u tankim filmovima smanjuje sa<br />dopiranjem. Priprema elektroda specifičnih geometrija pogodnih za tunabilna<br />merenja različitim tehnikama depozicije bio je drugi cilj istraživanja. Tehnika spaterovanja u kombinaciji sa laserskim uklanjanjem, inkdžet &scaron;tampa i fotolitografija<br />su kori&scaron;ćene za pripremu kružnih i koplanarnih elektroda na povr&scaron;ini barijum<br />titanatnih tankih filmova. Uticaj procesnih parametara svake od pomenutih<br />metoda na dimenzionalnu preciznost pripremljenih elektroda je bio predmet istraživanja<br />u okviru teze. Odabrani laser se pokazao kao neprikladan za pripremu<br />elektroda na pripremljenim barijum titanatnim tankim filmovima. Inkdžet &scaron;tampa<br />se pokazala kao korisna u pripremi elektroda mikrometarskih fimenzija, dok je za<br />pripremu sofisticiranijih geometrija fotolitografija pokazala najbolje performanse.</p> / <p>In past few decades, ferroelectrics are recognized as good candidates for wide<br />range of applications. Barium titanate is one of the most investigated perovskite<br />materials due to typical ferroelectric behavior at room temperature, with hysteresis<br />dependence of the polarization and electric field. Specified properties<br />of BaTiO₃ make this material useful in production of capacitors, memories,<br />sensors, etc. Nevertheless, paraelectric phase of BaTiO₃ may have application<br />in production of microwave tunable devices. Barium titanate shows paraelectric<br />behavior at temperatures above the Currie temperature (120 &deg;C) and it is great<br />challenge to make material paraelectric at room temperature. Partial substitution<br />of Ba²⁺ or Ti⁴⁺ ions, by Sr²⁺ or Zr⁴⁺, respectively, decreases the Currie temperature<br />of barium titanate and moves phase transition ferroelectric/paraelectric<br />to lower temperatures. Bulk BaTiO₃was often investigated in order to improve<br />structure and functionality by addition of dopant, but do not have practical<br />application in microwave tunable technologies. On the other hand, with the<br />trend of overall miniaturization of electronic devices, thin films are recognized<br />as good candidates for production of tunable devices. One of the aims in this<br />research was investigation of structural and functional properties of barium<br />titanate based thin films, BaTiO₃, Ba_1-xSrxTiO₃ (x=0,1, 0,2, 0,3 i 0,4) and<br />BaTi_1-xZrxO₃ (x=0,1 i 0,2), prepared by chemical solution deposition. Metal<br />salts of BaCO₃, C₄H₆O₄Sr and ZrOCl₂ H₂O and Ti(OCH₂CH₂CH₂CH₃)₄were<br />separetly disolved in acetic environment and mixed in clear transparent sols.<br />Inkjet printing and spin coating were used for deposition of functional BaTiO3<br />based fims. After deposition prepared films were thermally treated at different<br />temperatures up to 1000 &deg;C. In dependence of sol concentration thickness of<br />obtained films is from 100 to 700 nm and grain size is few tens of nanometers. Structural characterization confirmed changes in structure of barium titanate thin<br />films by addition of Sr^₂₊ i Zr⁴⁺. Tetragonal (ferroelectric) phase of BaTiO₃ is<br />confirmed by X-ray diffraction and Raman spectroscopy. On the other hand, decreasing<br />of tetragonality was noticed in doped samples. Changes in functionality<br />of doped BaTiO₃ thin films were analyzed by dielectric and ferroelectric measurements.<br />Performed analysis confirmed ferroelectric behavior of barium titanate<br />thin films, and decrease in ferroelectric answer of doped films. Investigation of<br />possibility of complex shaped electrodes preparation,suitable for tunability measurements, by different deposition techniques was the second goal of this research.<br />Sputtering technique in combination with laser removal, inkjet printing and photolithography were used for preparation of complex circular and coplanar electrodes<br />on the surface of barium titanate based thin films. Influence of processing<br />parameters for the each of mentioned technique on dimensional precision of prepared<br />electrodes was investigated. Selected laser was not appropriate for production<br />of electrodes on prepared barium titanate based thin films. Inkjet printing<br />was useful for production of electrodes in micrometer range, but for more sophisticated<br />geometries photolithography shows the best performance.</p>

Methods for reliability assessment and a deep understanding of degradation mechanisms are important for product and process development. In this work, reliability under electrical stress of a state-of-the-art integrated low-temperature PVD PZT Film stack is discussed. DC and AC lifetime under electric stress are investigated experimentally over wide ranges of temperature and applied electric field. Empirical Weibull analysis and comparison of the obtained Weibull slope is used to evaluate suitable acceleration ranges for empirical testing. Changes of the Weibull slope above a temperature of 150 °C and gradual change over voltage acceleration in the range of 100 kV/cm to 200 kV/cm were found. This indicates that accelerated lifetime testing in the temperature range below 150 °C is possible and caution is required for voltage acceleration. The results of this study are also published in Ref. (a). Closing the literature gap, time to breakdown data under unipolar AC electric stress is presented. Comparison with results obtained under DC electric stress reveals that the DC degradation mechanism still dominates under unipolar AC load. This observation was found to hold over tested AC frequency, DC offset, and temperature ranges. As consequence, AC lifetime can be predicted based on DC time to breakdown experiments (b). To enhance the physical understanding of degradation and breakdown, variation of the leakage current over time during electrical load is analyzed. An enhanced physical model for leakage current degradation is proposed and degradation kinetics are studied experimentally. For the first time, more than one defect species being active and manifesting in leakage current degradation of perovskite oxides are proposed and experimental evidence is presented to substantiate the hypotheses. Model predictions and experimental results are found to be in excellent agreement. The proposed characterization method allows for characterization of contributing defect types by associated charge and true activation energy (c). Based on experimental observations, a direct connection between leakage current degradation mechanism and time dependent dielectric breakdown (TDDB) mechanism is proposed and formulated in a physical model. For the first time, kinetics of leakage current degradation and TDDB are successfully linked, using new evaluation methods for the experimental data obtained under DC and AC electrical stress. This pioneering connection between leakage current and breakdown ultimately leads to the fundament of a comprehensive HALT model. Fundamental implications of the new findings on reliability testing of high-k dielectrics are discussed. / Methoden zur Zuverlässigkeitsbewertung und ein tiefes Verständnis der Degradationsmechanismen sind wichtig für die Produkt- und Prozessentwicklung. In dieser Arbeit wird die Zuverlässigkeit eines auf dem Stand der Technik befindlichen integrierten niedertemperatur PVD PZT Dünnschichtstapels unter elektrischer Last diskutiert. Lebenszeit unter Gleichstrom- (DC) und Wechselstromlast (AC) werden experimentell über weite Bereiche der Temperatur und angelegter Feldstärke untersucht. Empirische Weibull Analyse und Vergleich der erhaltenen Weibull-Module werden verwendet, um Beschleunigungsbereiche für empirische Testverfahren zu bewerten. Eine Veränderung der Weibull-Module oberhalb von 150 °C und eine graduelle Veränderung für Spannungsbeschleunigung im Bereich von 100 kV/cm bis 200 kV/cm wurden festgestellt. Dies weist darauf hin, dass beschleunigte Lebenszeittests im Temperaturbereich unterhalb von 150 °C möglich sind, Spannungsbeschleunigung jedoch mit hoher Vorsicht zu bewerten ist. Die Ergebnisse dieser Untersuchung sind ebenfalls in Ref. (a) veröffentlicht. Durch die Präsentation von Durchbruchzeiten unter unipolarer AC-Belastung wird eine Forschungslücke geschlossen. Ein Vergleich mit Ergebnissen, die unter Gleichstrombelastung erhoben wurden zeigt, dass Degradationsmechanismen, die unter DC aktiv sind unter unipolarer AC-Belastung das Durchbruchverhalten weiterhin dominieren. Diese Beobachtung hat Bestand über die untersuchten Bereiche von AC-Frequenz, DC-Versatz und Temperatur. Daraus folgt, dass Lebenszeit unter AC-Belastung durch Experimente unter DC vorhergesagt werden kann (b). Um das physikalische Verständins von Degradation und Durchbruch zu erweitern, wird die Veränderung des Leckstroms über elektrischer Belastungszeit analysiert. Ein erweitertes physikalisches Modell für die Leckstromdegradation wird vorgeschlagen und die Degradationskinetik wird experimentell untersucht. Zum ersten Mal, werden mehr als zwei aktive Defektarten, die sich in der Leckstromdegradation von Perowskit Oxiden abzeichnen eingebracht und durch experimentelle Befunde untermauert. Modellvorhersagen und experimentelle Ergebnisse zeigen eine exzellente Übereinstimmung. Die vorgeschlagene Charakterisierungsmethode erlaubt die Charakterisierung der beteiligten Defektarten über zugeordneter Ladung und wahrer Aktivierungsenergie (c). Basierend auf experimentellen Beobachtungen wird ein direkter Zusammenhang zwischen Leckstromdegradation und zeitabhängigem dielektrischen Durchbruchmechanismus (TDDB) vorgeschlagen und in einem physikalischen Modell abgebildet. Zum ersten Mal werden die Kinetik hinter Leckstromdegradation und TDDB über neue Auswerteverfahren der erhobenen experimentellen Daten unter DC- und AC-Belastung erfolgreich verknüpft. Dieser wegweisende Zusammenhang zwischen Leckstromdegradation und Durchbruch legt das Fundament zu einer verständnisbasierten stark beschleunigten Grenzlastprüfung. Grundlegende Auswirkungen der neuen Ergebnisse auf Zuverlässigkeitstestmethoden von high-k Dielektrika werden diskutiert.

Litiumjon-batterier har blivit väldigt populära för tillämpning i fordon. Den här teknologin har fler olika kemier att erbjuda som kontinuerligt förbättras. Litium-titanat-oxid-batterier använder (LTO) LTO som anod och erbjuder långt cyklingsliv samt minskar risk för SEI-bildning och litiumplätering.  Det här examensarbetet siktade på att undersöka om LTO-batterier kan användas som startbatterier i kommersiella fordon. Metodologin inkluderade två motorstart försök med en kommersiell 12s1p LTO-modul, laddnings/urladdningtester med en kommersiell LTO-cell med nominell spänning 2.3V samt överurladdningstester med byggda pouchceller. Materialet för pouchceller extraherades från en kommersiell LTO-cell och sedan studerades med SEM-EDX före och efter överurladdningstesterna. Resultatet visade att LTO-batterier kan användas som startbatterier i en diesel V8 motor även vid 39%SoC. Dessutom visade simuleringar att LTO-batterier kan användas inom Kinetic Energy Recovery System (KERS) tillämpning och behålla 60% SoC efter 500 laddning/urladdnings cykler. Resultaten från både KERS och motorstarterna visade att LTO är en lovande kandidat för ersättning av blybatterier. Laddnings/urladdnings tester visade att en kommersiell 12s1p LTO modul kan maximalt uppnå 73%SoC när den laddas med fordon-liknande strömmar. Däremot var SoC oberoende av laddningsström. Överurladdningstester med pouchceller visade att det är relativt ofarligt att urladda LTO 0.4V under spänningsgränsen utan stora ökningar i impedans eller stor kapacitetsförlust. Största förluster kopplades till åldring av NMC-baserade positiva elektroden. / Lithium ion batteries have become quite popular in vehicle applications in the past few decades. This technology offers multiple chemistries to choose from, that are continuously studied and improved. Lithium-titanate-oxide (LTO) batteries use LTO material as an anode, providing long cycling life, as well as essentially eliminating risk for SEI formation and lithium plating.  This Master thesis project aimed to investigate how well LTO-based lithium-ion batteries can perform in Start Ignition Lighting (SLI) application in commercial vehicles. The methodology included two engine crank tests with a commercial 12s1p LTO module, charge/discharge tests on a commercial LTO cell with nominal voltage 2.3V, as well as overdischarge cycling tests on assembled pouch cells. The materials for the pouch cells were extracted from a commercial LTO cell and later analysed with SEM-EDX before and after overdischarge tests. The results demonstrated that LTO-based Li-ion batteries can be successfully start a diesel V8 engine even at 39% SoC. Furthermore, when simulating an urban vehicle with an implemented Kinetic Energy Recovery System (KERS) application, a commercial cell LTO cell achieved and retained around 60\%SoC throughout 500 charge/discharge cycles. Combined results from KERS and engine start tests imply that LTO is a strong candidate for replacing lead-acid in these applications. Charge/discharge tests showed that commercial 12s1p LTO cell can maximum reach around 73%SoC when charged in a vehicle-like way. However, this maximum SoC limit was more or less independent of applied charging current. Furthermore, electrochemical overdischarge tests on the pouch cells demonstrated that it is relatively safe to overdischarge the cell 0.4V below the specified safety limit without significant rise in impedance or capacity fade. Major performance losses were attributed to the aging of the NMC-based positive electrode.

Ferroic materials play an increasingly important role in novel (nano-)electronic applications. Recently, research on domain walls (DWs) received a big boost by the discovery of DW conductivity in bismuth ferrite (BiFeO3 ) and lead zirconate titanate (Pb(Zrx Ti1−x )O3) ferroic thin films. These achievements open a realistic and unique perspective to reproducibly engineer conductive paths and nanocontacts of sub-nanometer dimensions into wide-bandgap materials. The possibility to control and induce conductive DWs in insulating templates is a key step towards future innovative nanoelectronic devices [1]. This work focuses on the investigation of the charge transport along conductive DWs in ferroelectric single crystals. In the first part, the photo-induced electronic DC and AC charge transport along such DWs in lithium niobate (LNO) single crystals is examined. The DC conductivity of the bulk and DWs is investigated locally using piezoresponse force microscopy (PFM) and conductive AFM (c-AFM). It is shown that super-bandgap illumination (λ ≤ 310 nm) in combination with (partially) charged 180° DWs increases the DC conductivity of the DWs up to three orders of magnitude compared to the bulk. The DW conductivity is proportional to the charge of the DW given by its inclination angle α with respect to the polar axis. The latter can be increased by doping the crystal with magnesium (0 to 7 mol %) or reduced by sample annealing. The AC conductivity is investigated locally utilizing nanoimpedance microscopy (NIM) and macroscopic impedance measurements. Again, super-bandgap illumination increases the AC conductivity of the DWs. Frequency-dependent measurements are performed to determine an equivalent circuit describing the domains and DWs in a model system. The mixed conduction model for hopping transport in LNO is used to analyze the frequency-dependent complex permittivity. Both, the AC and DC results are then used to establish a model describing the transport along the conductive DW through the insulating domain matrix material. In the last part, the knowledge obtained for LNO is applied to study DWs in lithium tantalate (LTO), barium titanate (BTO) and barium calcium titanate (BCT) single crystals. Under super-bandgap illumination, conductive DWs are found in LTO and BCT as well, whereas a domain-specific conductivity is observed in BTO.

Ferroic materials play an increasingly important role in novel (nano-)electronic applications. Recently, research on domain walls (DWs) received a big boost by the discovery of DW conductivity in bismuth ferrite (BiFeO3 ) and lead zirconate titanate (Pb(Zrx Ti1−x )O3) ferroic thin films. These achievements open a realistic and unique perspective to reproducibly engineer conductive paths and nanocontacts of sub-nanometer dimensions into wide-bandgap materials. The possibility to control and induce conductive DWs in insulating templates is a key step towards future innovative nanoelectronic devices [1]. This work focuses on the investigation of the charge transport along conductive DWs in ferroelectric single crystals. In the first part, the photo-induced electronic DC and AC charge transport along such DWs in lithium niobate (LNO) single crystals is examined. The DC conductivity of the bulk and DWs is investigated locally using piezoresponse force microscopy (PFM) and conductive AFM (c-AFM). It is shown that super-bandgap illumination (λ ≤ 310 nm) in combination with (partially) charged 180° DWs increases the DC conductivity of the DWs up to three orders of magnitude compared to the bulk. The DW conductivity is proportional to the charge of the DW given by its inclination angle α with respect to the polar axis. The latter can be increased by doping the crystal with magnesium (0 to 7 mol %) or reduced by sample annealing. The AC conductivity is investigated locally utilizing nanoimpedance microscopy (NIM) and macroscopic impedance measurements. Again, super-bandgap illumination increases the AC conductivity of the DWs. Frequency-dependent measurements are performed to determine an equivalent circuit describing the domains and DWs in a model system. The mixed conduction model for hopping transport in LNO is used to analyze the frequency-dependent complex permittivity. Both, the AC and DC results are then used to establish a model describing the transport along the conductive DW through the insulating domain matrix material. In the last part, the knowledge obtained for LNO is applied to study DWs in lithium tantalate (LTO), barium titanate (BTO) and barium calcium titanate (BCT) single crystals. Under super-bandgap illumination, conductive DWs are found in LTO and BCT as well, whereas a domain-specific conductivity is observed in BTO.