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Investigation of the Electrochromic Properties of V2O5 Thin Films Investigation of the electrochromic properties of V2O5 thin films deposited by sputtering : comparison of High Power Impulse Magnetron Sputtering (HiPIMS) vs conventional Radio Frequency Magnetron Sputtering (RFMS) Giljoo Song To cite this version: Giljoo Song. Investigation of the electrochromic properties of V2O5 thin films deposited by sputtering : comparison of High Power Impulse Magnetron Sputtering (HiPIMS) vs conventional Radio Frequency Magnetron Sputtering (RFMS). Material chemistry. Université de Bordeaux, 2019. English. NNT : 2019BORD0062. tel-03221282 HAL Id: tel-03221282 https://tel.archives-ouvertes.fr/tel-03221282 Submitted on 8 May 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSE PRÉSENTÉE POUR OBTENIR LE GRADE DE DOCTEUR DE L’UNIVERSITÉ DE BORDEAUX ÉCOLE DOCTORALE SPÉCIALITÉ : PHYSICO-CHIMIE DE LA MATIÈRE CONDENSÉE Giljoo SONG Investigation of the electrochromic properties of V2O5 thin films deposited by sputtering : comparison of High Power Impulse Magnetron Sputtering (HiPIMS) vs conventional Radio Frequency Magnetron Sputtering (RFMS) Sous la direction de : Aline Rougier Soutenance prévue le 7 Mai 2019 Membres du jury : Mme. BADDOUR Rita, Directrice de Recherche, CNRS-ICMPE, Thiais Rapportrice M. KIM Jongwook, Maitre de Conférences, Ecole Polytechnique, Palaiseau Examinateur Mme. LEE Caroline Sunyong, Professeure, Université de Hanyang, Corée du sud Examinatrice M. MAGLIONE, Mario, Directeur de Recherche, CNRS-ICMCB, Pessac Directeur M. PIERSON, Jean-François, Professeur, Université de Lorraine, Nancy Rapporteur Mme. ROUGIER, Aline, Directrice de Recherche, CNRS-ICMCB, Pessac Directrice de thèse Acknowledgments First of all, I would like to express my sincere gratitude to Dr. Mario Maglione, Director of ICMCB-CNRS, for welcoming me at ICMCB and also providing a great scientific environment. Many thanks to my supervisor Dr. Aline ROUGIER for wonderful guidance. There is no doubt that she did teach me based on not only their great scientific knowledge but also their sincere care and love. I would like to thank all the jury members for their efforts to review and judge this work. I would like to thank very much to my company SK Hynix and Hyunyul PARK, Sungmin HWANG, Ilyoung LIM in SK Hynix for great support and help. My deep gratitude to my dear friends for the support and encouragements, Khawla ZRIKEM, Shian GUAN, Romain FUTSCH, Dr. Issam MJEJRI and Dr. Mathias DA ROCHA. I am thankful to all the following people from the ICMCB and PLACAMAT for the help, experiments they did or the effective discussions: Lionel TEULE-GAY and Dominique MICHAU, Sonia BUFFIÉRE, Eric LEBRAUD, Christine LABRUGERE, Alexandre FARGUES and Nicola PENIN. My deep gratitude to Hyungjin PARK and his family, Dr. Eungjang LEE, Dr. Kayoung KIM and Dr. Daehoon PARK for their encouragements during my Ph.D. period. Finally, this thesis is dedicated to my wife Youngeun and to my daughter, Hyojin and Hyowon and to my parents and parents-in-law. Caractérisation des propriétés électrochromes de couches minces de V2O5 déposées par pulvérisation cathodique : comparaison de la méthode HiPIMS et de la méthode RFMS Les matériaux et dispositifs électrochromes sont capables de modifier leurs propriétés optiques sous l’application d’une tension. De plus en plus présents dans notre vie quotidienne, leur domaine d’application s’étend des rétroviseurs automobiles (Première commercialisation fin des années 80 par Gentex sur une technologie à base de viologènes pour une production aujourd’hui de plus de 80 Millions par an), aux fenêtres intelligentes (bâtiments, toits de voiture, augmentation prévue de 13%/ans, soit un coût de $2.6 billions en 2020 pour les vitrages) à l’affichage. Parmi les différents matériaux électrochromes, les oxydes de métaux de transition ont suscité un vif intérêt suite aux travaux de Deb à la fin des années 60, montrant la commutation réversible de couches minces d’oxyde de tungstène WO3. WO3, de coloration cathodique, reste aujourd’hui l’état de l’art des matériaux électrochromes, il est communément associé à l’oxyde de nickel NiO dans les dispositifs commercialisés. Toutefois l’association de ces deux oxydes souffre de certaines limitations telles qu’une incompatibilité acido-basique. L’oxyde de Vanadium, V2O5, est un candidat de choix pour substituer NiO. Ce travail de thèse, dédié à la comparaison des propriétés électrochromes de couches minces de V2O5 déposées par pulvérisation cathodique utilisant la méthode conventionnelle et la méthode HiPIMS (High Power Impulse Magnetron Sputtering) est divisé en quatre grandes parties. La première partie, découpée en trois chapitres, précise l’état de l’art des matériaux et dispositifs électrochromes avec des détails concernant les applications actuelles (Chapt. 1), introduit les caractéristiques notamment structurales de l’oxyde étudié V2O5 (Chapt. 2) et se conclut par une description de la technique de dépôt utilisée, la pulvérisation cathodique (Chapt. 3). Les résultats expérimentaux font l’objet des trois parties suivantes et concernent dans un premier temps, la caractérisation physico-chimique et les propriétés électrochromes (Electrochimique et optique) des couches minces V2O5. La partie C s’attache plus précisément à la compréhension du mécanisme électrochrome mis en jeu, tandis que l’intégration des couches de V2O5 en dispositifs complets est rapportée dans la dernière partie. La première étape de ce travail de thèse a consisté en l’optimisation des paramètres de dépôt. Majoritairement trois paramètres ont été étudiés : la puissance, la pression totale et la pression partielle en oxygène à partir de l’utilisation de deux cibles, du Vanadium métallique V, et de l’oxyde V2O5. La détermination des conditions optimums a été effectuée en caractérisant électrochimiquement et optiquement les films déposés. Visuellement, les films frais de dépôt sont de couleur orange. Les conditions de dépôt sélectionnées sont regroupées dans le tableau I. Tableau I : Conditions de dépôt de films VxOy, Puissance, Pression totale et Pression partielle en oxygène, à partir d’une cible métallique ou d’une cible d’oxyde. Cible V Cible V2O5 Puissance (W) 200 150 PTot (Pa) 2 2 PO2 (%) (Pa) 20 2 La caractérisation structurale des films, menée en diffraction des rayons X en configuration en angle rasant montre des films cristallisés en symétrie orthorhombique (G.E. Pmmn) pour les films déposés à partir d’une cible métallique, tandis qu’ils sont amorphes à partir d’une cible d’oxyde (Fig. 1a). Les clichés de microscopie électronique à balayage mettent en évidence des états de surface assez perturbés (Fig. 1b). Figure 1 : a) Diffractogrammes de Rayons X des films V2O5 déposés à partir d’une cible métallique (Bleu) et d’une cible oxyde (V2O5), b) Morphologie associée. G V targetG V2O5 target 1 ੇG 1 ੇG La caractérisation électrochimique des films a été menée par voltampérométrie cyclique pour l’évaluation de la durabilité et par chronoampérométrie pour l’évaluation de la cinétique. Les films ont été cyclés en cellule à trois électrodes en milieu électrolyte lithié et sodé suivant la chaîne électrochimique V2O5/Li (Na) électrolyte /Pt vs ECS (Fig. 2). La signature des voltampérogrammes montre la présence de deux pics réversibles en milieu lithié tandis que la forme du voltampérogramme est beaucoup plus écrasée en milieu sodé. Toutefois, dans les deux milieux, les films commutent de façon réversible d’orange à vert et bleu en cyclage. Ce multichromisme, propre à l’oxyde V2O5, est associé à une modulation en transmittance de l’ordre de 40 % à 450 nm avec un déplacement du seuil de transmittance vers les plus faibles longueurs d’onde en réduction. Figure 2 : Voltampérogrammes en cellule à trois électrodes, V2O5/Li (Na) electrolyte /Pt vs ECS pour une vitesse de balayage de 10 mV/s et transmittances associées dans les 4 états (frais de dépôt, réduit à 0.2 V et -1 V et oxydé à 1 V). (a, c) correspondent aux films déposés à partir d’une cible métallique et (b, d) aux films déposés à partir d’une cible oxyde. Des caractéristiques électrochromes similaires, pour les films déposés à partir d’une cible oxyde sont observées, avec toutefois une tenue en cyclage beaucoup plus faible associée à une « dé-cohésion » des films très rapide. Afin de pallier à cette durabilité limitée reliée majoritairement à une morphologie de mauvaise qualité, des films ont été déposés par HiPIMS. Cette méthode ayant été mise en place pour la première fois au laboratoire, un travail d’optimisation a dû être mené. Amorphes et denses, les films déposés par HiPIMS dans des conditions optimisées de durée de pulsation de 45 μs et un taux de répétition de 1200 Hz adoptent un comportement électrochrome très proche des films déposés de façon conventionnelle. Toutefois, ils montrent une meilleure durabilité associée à une morpholgie qui évolue peu en cyclage (Fig. 3). Figure 3 : Capacité en cyclage pour les cellules V2O5/Li (Na) electrolyte /Pt vs ECS (Electrode au Calomel Saturé) à partir de films V2O5 déposés à partir d’une cible métallique, d’une cible d’oxyde ou par la méthode HiPIMS ; Evolution des morphologies associées. La détermination du mécanisme électrochrome fait l’objet de la partie C. Cette étude a été menée sur les films cristallisés déposés à partir d’une cible métallique. Avant de débuter les caractérisations ex-situ sur les films réduits leur effet mémoire a été évalué par comparaison des transmittances optiques après réduction à 0,2 V et -1,0 V pour 120 s et après une période d’un mois sans potentiel appliqué. Dans ces conditions, aucune modification des propriétés optiques n’est enregistrée.
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