Molecular-based Magnetoresistance Devices at Room Temperature
[eng] In this doctoral thesis a series of computational and experimental studies of molecular magnetoresistance devices at room temperature is presented. This sort of devices is included in the molecular electronics framework with the objective of studying molecular systems to build up molecular dev...
| Author: | |
|---|---|
| Format: | Doctoral thesis |
| Status: | Published version |
| Publication date: | 2021 |
| Country: | España |
| Institution: | Universidad de Barcelona |
| Repository: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/180411 |
| Online Access: | https://hdl.handle.net/2445/180411 http://hdl.handle.net/10803/672545 |
| Access Level: | Open access |
| Keyword: | Nanociència Electrònica molecular Magnetoresistència Transport d'electrons Teoria del transport Espintrònica Nanoscience Molecular electronics Magnetoresistance Electron transport Transport theory Spintronics |
| _version_ | 1878739974500646912 |
|---|---|
| author | Martín Rodríguez, Alejandro |
| author_browse | Martín Rodríguez, Alejandro |
| author_facet | Martín Rodríguez, Alejandro |
| author_role | author |
| collection | Dipòsit Digital de la UB |
| description | [eng] In this doctoral thesis a series of computational and experimental studies of molecular magnetoresistance devices at room temperature is presented. This sort of devices is included in the molecular electronics framework with the objective of studying molecular systems to build up molecular devices. Particularly, molecular systems with unpaired electrons are potential candidates to mimic and miniaturizing nowadays spin valves, widely employed in magnetic memories, besides adding new functionalities through chemical modification. Finding out functional candidates at room temperature is crucial to the posterior application on electronic devices. The first chapter introduces common molecular electronics phenomenology and the most used experimental techniques. Landauer’s formalism is explained in detail along with Green’s function formalism, which permits to describe the electron as a traveling wave from one electrode to the other via an applied bias. Different electronic structure and quantum transport codes employed to perform theoretical calculations are discussed. In the second chapter, a supramolecular landscape of CoII-5,15-diphenylporphyrin (CoDPP) and CoII-Porphyrin (CoP) is proposed to explain the high conductance signatures observed in STM- Break Junction experiments when both gold electrodes are functionalised with pyridine-4-yl- metanthiol (PyrMT) and 4-mercaptopyridine (PyrT). Afterwards, the discussion is expanded to CoII, NiII, CuII and ZnII metallodiphenylporphyrins to explore the magnetoresistance of these systems in the third chapter. Theoretical calculations allow understanding qualitatively the observed magnetoresistance on CoII and CuII metalloporphyrins. The fourth chapter leaves unimolecular devices and tackles, in two collaborations, the computational study of molecular monolayer junctions. The first contribution was in collaboration with Dr. Monakhov’s group (IOM, Leipzig), in which the monolayer junction CuLn(L·SMe)2(OOCMe)2(NO3)] (Ln = Gd, Tb, Dy i Y, x = 0.75-1) is studied employing an eutectic gallium and indium electrode (EGaIn). The experimental current independence of the lanthanide is corroborated in the computational study. A second collaboration with Dr. Nijhuis (NUS, Singapore) and Dr. Harding (Walailak University) studies the first FeIII spin crossover system at room temperature: [FeIII(qsal-I)2]NTf2 (qsal-I = 4-iodo-2-[(8- quinolylimino)methyl]phenolate). In this study an explicit model of EGaIn electrode is included to explain the observed conductance according to the FeIII spin state. The fifth chapter faces, both computational and experimentally, the building of spintronic devices based on Hofmann-type clathrate monolayers {CoII(PyrT)2Pt(CN)4} (PyrT = 4- mercaptopyridine). In the experimental section, the synthesis and characterisation of the monolayer using XPS, ellipsometry, AFM and C-AFM images is explained. Preliminary results about conductance at the molecular level were obtained in blinking STM experiments. The theoretical study permits the understanding of the observed conductance signatures and gives a qualitative explanation to the observed magnetoresistance. The last chapter goes back to unimolecular nanojunctions to study the thermoelectric properties of magnetic complexes. In this chapter, VII, FeII, CoII and NiII metallocenes, GdIII and EuII sandwich compounds and CoII and FeII complexes of the form [MII(SCN)2+x(py)4-x] (x = 0-2, py = pyridine) are theoretically explored to find out common characteristics for potential candidates to future experiments. |
| eu_rights_str_mv | openAccess |
| format | doctoralThesis |
| id | ES_cb6a93e0646f1cdd97f4de983c8f388c |
| institution | Universidad de Barcelona |
| instname_str | Universidad de Barcelona |
| network_acronym_str | ES |
| network_name_str | España |
| oai_identifier_str | oai:diposit.ub.edu:2445/180411 |
| publishDate | 2021 |
| publishDateSort | 2021 |
| publisher | Universitat de Barcelona |
| publisherStr | Universitat de Barcelona |
| reponame_str | Dipòsit Digital de la UB |
| spelling | Molecular-based Magnetoresistance Devices at Room Temperature Martín Rodríguez, Alejandro Nanociència Electrònica molecular Magnetoresistència Transport d'electrons Teoria del transport Espintrònica Nanoscience Molecular electronics Magnetoresistance Electron transport Transport theory Spintronics [eng] In this doctoral thesis a series of computational and experimental studies of molecular magnetoresistance devices at room temperature is presented. This sort of devices is included in the molecular electronics framework with the objective of studying molecular systems to build up molecular devices. Particularly, molecular systems with unpaired electrons are potential candidates to mimic and miniaturizing nowadays spin valves, widely employed in magnetic memories, besides adding new functionalities through chemical modification. Finding out functional candidates at room temperature is crucial to the posterior application on electronic devices. The first chapter introduces common molecular electronics phenomenology and the most used experimental techniques. Landauer’s formalism is explained in detail along with Green’s function formalism, which permits to describe the electron as a traveling wave from one electrode to the other via an applied bias. Different electronic structure and quantum transport codes employed to perform theoretical calculations are discussed. In the second chapter, a supramolecular landscape of CoII-5,15-diphenylporphyrin (CoDPP) and CoII-Porphyrin (CoP) is proposed to explain the high conductance signatures observed in STM- Break Junction experiments when both gold electrodes are functionalised with pyridine-4-yl- metanthiol (PyrMT) and 4-mercaptopyridine (PyrT). Afterwards, the discussion is expanded to CoII, NiII, CuII and ZnII metallodiphenylporphyrins to explore the magnetoresistance of these systems in the third chapter. Theoretical calculations allow understanding qualitatively the observed magnetoresistance on CoII and CuII metalloporphyrins. The fourth chapter leaves unimolecular devices and tackles, in two collaborations, the computational study of molecular monolayer junctions. The first contribution was in collaboration with Dr. Monakhov’s group (IOM, Leipzig), in which the monolayer junction CuLn(L·SMe)2(OOCMe)2(NO3)] (Ln = Gd, Tb, Dy i Y, x = 0.75-1) is studied employing an eutectic gallium and indium electrode (EGaIn). The experimental current independence of the lanthanide is corroborated in the computational study. A second collaboration with Dr. Nijhuis (NUS, Singapore) and Dr. Harding (Walailak University) studies the first FeIII spin crossover system at room temperature: [FeIII(qsal-I)2]NTf2 (qsal-I = 4-iodo-2-[(8- quinolylimino)methyl]phenolate). In this study an explicit model of EGaIn electrode is included to explain the observed conductance according to the FeIII spin state. The fifth chapter faces, both computational and experimentally, the building of spintronic devices based on Hofmann-type clathrate monolayers {CoII(PyrT)2Pt(CN)4} (PyrT = 4- mercaptopyridine). In the experimental section, the synthesis and characterisation of the monolayer using XPS, ellipsometry, AFM and C-AFM images is explained. Preliminary results about conductance at the molecular level were obtained in blinking STM experiments. The theoretical study permits the understanding of the observed conductance signatures and gives a qualitative explanation to the observed magnetoresistance. The last chapter goes back to unimolecular nanojunctions to study the thermoelectric properties of magnetic complexes. In this chapter, VII, FeII, CoII and NiII metallocenes, GdIII and EuII sandwich compounds and CoII and FeII complexes of the form [MII(SCN)2+x(py)4-x] (x = 0-2, py = pyridine) are theoretically explored to find out common characteristics for potential candidates to future experiments. [cat] En aquesta tesi doctoral es presenta una sèrie d’estudis computacionals i experimentals sobre dispositius moleculars magnetoresistents a temperatura ambient. Aquesta mena de dispositius s’engloben dins de l’electrònica molecular, que té com a objectiu l’estudi de sistemes moleculars per l’elaboració de components electrònics. Particularment, els sistemes moleculars amb electrons desaparellats són candidats potencials a mimetitzar i miniaturitzar les actuals vàlvules d’espí, àmpliament emprades en memòries magnètiques, a més de poder afegir noves funcionalitats a través de la modificació química d’aquests dispositius. Trobar candidats funcionals a temperatura ambient és crucial per a la posterior aplicació en dispositius electrònics. En el primer capítol s’introdueix la fenomenologia típica de l’electrònica molecular i les tècniques experimentals més emprades en el seu estudi. S’explica en profunditat el formalisme de Landauer en conjunció amb el formalisme de Green, que permet la descripció de l’electró com a una ona viatjant d’un elèctrode a un altre per mitjà d’una diferència de voltatge. Es discuteixen diferents codis d’estructura electrònica i de transport quàntic que s’utilitzen per realitzar càlculs teòrics. En el segon capítol, es proposen, a través de càlculs computacionals, diferents interaccions supramoleculars de la CoII-5,15-difenilporfirina (CoDPP) i CoII-porfirina (CoP) per explicar les altes conductàncies observades en experiments STM-Break Junction quan els elèctrodes d’or es funcionalitzen amb piridina-4-yl-metantiol (PyrMT) i 4-mercaptopiridina (PyrT). Posteriorment, la discussió s’amplia a les metal·lodifenilporfirines de CoII, NiII, CuII i ZnII per explorar la magnetoresistència d’aquests sistemes en el capítol tercer. Els càlculs teòrics permeten comprendre qualitativament la magnetoresistència observada en les metal·loporfirines de CoII i CuII. El quart capítol abandona els dispositius unimoleculars i aborda, en dues col·laboracions, l’estudi computacional de juntes moleculars monocapa. La primera col·laboració es va dur a terme amb el grup del Dr. Monakhov (IOM, Leipzig), en la qual s’estudia la junta monocapa [CuLn(L·SMe)2(OOCMe)2(NO3)] (Ln = Gd, Tb, Dy i Y, x = 0.75-1) mitjançant un elèctrode eutèctic de gal·li i indi (EGaIn). La independència experimental de la corrent respecte del lantànid queda corroborada en l’estudi computacional. Una segona col·laboració amb el Dr. Nijhuis (NUS, Singapur) i el Dr. Harding (Walailak University) estudia el primer sistema de FeIII amb propietats de transició d’espí a temperatura ambient: [FeIII(qsal-I)2]NTf2 (qsal-I = 4-iodo-2- [(8-quinolilimino)metilfenolat). En aquest estudi s’inclou un model explícit de l’elèctrode EGaIn que explica la conductància observada segons l’estat d’espín del FeIII. El cinquè capítol afronta, tant experimental com teòricament, la formació de dispositius espintrònics basats en monocapes de tipus clatrat de Hofmann {CoII(PyrT)2Pt(CN)4} (PyrT = 4- mercaptopiridina). En la secció experimental, s’explica la síntesi i caracterització de la monocapa mitjançant XPS, elipsometria i imatges AFM i C-AFM. Resultats preliminars de la conductància a nivell molecular s’obtenen mitjançant experiments de blinking STM. L’estudi teòric permet entendre les senyals de conductància observades i, a més, explicar de manera qualitativa la magnetoresistència observada. En l’últim capítol es retorna a les nanojuntes unimoleculars per estudiar les propietats termoelèctriques de complexos magnètics. En aquest capítol s’exploren teòricament metal·locens de VII, FeII, CoII i NiII, compostos tipus sandvitx de GdIII i EuII i complexos de CoII i FeII de la mena [MII(SCN)2+x(py)4-x] (x = 0-2, py = piridina) per trobar característiques comunes a potencials candidats per futurs experiments. Universitat de Barcelona https://hdl.handle.net/2445/180411 http://hdl.handle.net/10803/672545 |
| spellingShingle | Molecular-based Magnetoresistance Devices at Room Temperature Martín Rodríguez, Alejandro Nanociència Electrònica molecular Magnetoresistència Transport d'electrons Teoria del transport Espintrònica Nanoscience Molecular electronics Magnetoresistance Electron transport Transport theory Spintronics |
| status_str | publishedVersion |
| title | Molecular-based Magnetoresistance Devices at Room Temperature |
| title_full | Molecular-based Magnetoresistance Devices at Room Temperature |
| title_fullStr | Molecular-based Magnetoresistance Devices at Room Temperature |
| title_full_unstemmed | Molecular-based Magnetoresistance Devices at Room Temperature |
| title_short | Molecular-based Magnetoresistance Devices at Room Temperature |
| title_sort | Molecular-based Magnetoresistance Devices at Room Temperature |
| topic | Nanociència Electrònica molecular Magnetoresistència Transport d'electrons Teoria del transport Espintrònica Nanoscience Molecular electronics Magnetoresistance Electron transport Transport theory Spintronics |
| topic_facet | Nanociència Electrònica molecular Magnetoresistència Transport d'electrons Teoria del transport Espintrònica Nanoscience Molecular electronics Magnetoresistance Electron transport Transport theory Spintronics |
| url | https://hdl.handle.net/2445/180411 http://hdl.handle.net/10803/672545 |