Investigation of novel ferroelectrics and their electrical and optical applicaitons
Notice bibliographique
Résumé
Ferroelectrics are considered essential components in a wide spectrum of electrical and optical applications, including but not limited to ferroelectric random access memory (FeRAM), piezoelectric transducers, and optical waveguides and modulators, owing to their remarkable ferroelectric, piezoelectric, and electro-optic properties. The research presented in this thesis provides a comprehensive investigation, including theoretical principles, fabrication technology, performance optimization, and electrical/optical applications, of two innovative ferroelectric materials, namely, Nd-doped bismuth titanate (BNdT) and bismuth ferrite (BFO). We start by describing the fabrication procedure, and then study the dependence of ferroelectric properties on various fabrication parameters. By varying the post annealing temperature and tuning the elemental constituents, ferroelectrics with optimized performance parameters are demonstrated in our work. Then, we further our study into the optical characterization, and provide a systematic investigation of BNdT optical properties for the first time. Optical parameters including the optical transmittance, refractive index, extinction coefficient, and optical band gap energy, are examined and their correlation with different fabrication variables and microstructure properties is studied both experimentally and theoretically. In the third part of this thesis, by introducing the optimized BNdT ferroelectric thin film as a seeding layer for the BFO, we report the first room temperature (RT) ferroelectric measurement of pure BFO.We further advance our study by investigating the photovoltaic nature of multiferroic BFO, and report enhanced photovoltaic performance of the BFO material in a graphene/polycrystalline BFO/Pt heterojunction structure for the first time. The unique properties of the graphene electrode lead to a short circuit current density of 61 μA/cm2 and an open circuit voltage of 0.52 V in the heterojunction. These values are much higher than the results previously reported in the literature. A theoretical model that takes into consideration the ferroelectric polarization, interface states, and energy band bending effect, is constructed to describe the ferroelectric photovoltaic effect and carrier transport behaviour for the first time. Key photovoltaic parameters, such as conversion efficiency, illumination intensity response, ON/OFF characteristics, minority carrier lifetime, and external quantum efficiency (EQE), are investigated through both theory and measurements. Finally, to improve the existing photovoltaic performance of the graphene/polycrystalline BFO/Pt heterojunction, two independent chemical and physical routines, are processed and compared. It can be seen that the photocurrent density exhibits a significant improvement from 61 μA/cm2 to 8.67 mA/cm2 (~150 fold) after HNO3 treatment, while a considerable enhancement of ~5 fold is seen with QDs filling/sensitizing. An optical application of a photosensitive detector and an electrical application of a tunable switch are also demonstrated as two interesting applications of the BFO photovoltaic effect. Research in the field of novel ferroelectrics continues to thrive, and a number of interesting theoretical and application studies are currently underway. The results achieved in this thesis may provide a useful understanding of the principles and properties of two such ferroelectrics, and can serve as assistance in future research perspectives.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».