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Hydrothermal Epitaxy of Functional Perovskite Thin Films

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Hydrothermal Epitaxy of Functional Perovskite Thin Films/ Ivan Alejandro Velasco-Davalos.
Author:	Velasco-Davalos, Ivan Alejandro,
Description:	1 electronic resource (123 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
Contained By:	Dissertations Abstracts International84-11B.
Subject:	Physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30450614
ISBN:	9798379462499

Hydrothermal Epitaxy of Functional Perovskite Thin Films
Velasco-Davalos, Ivan Alejandro,

Hydrothermal Epitaxy of Functional Perovskite Thin Films [electronic resource] /Ivan Alejandro Velasco-Davalos. - 1 electronic resource (123 pages)

Source: Dissertations Abstracts International, Volume: 84-11, Section: B.

Functional oxides and their thin film epitaxy have become increasingly requested and further improvement in the existing technologies of information storage and energy harvesting heavily depends on the performance of such heterostructures at the nanoscale. Ferroelectric materials show a spontaneous electric polarization, which can be switched repeatedly by applying an external electric field. Since the discovery of ferroelectric BaTiO3 as the first oxide ferroelectric, the period prior to 1988 was mainly restricted to modelling ferroelectric phase transitions and discovering new ones. However, the focus has been significantly changed in the nineties, when thin films were developed and integrated into semiconductors at the nanoscale. This down scaling and bi-stable polarization of ferroelectrics were attractive in memory devices through ferroelectric random access memory, smart cards etc., and in tunable microwave devices through phase shifters, delay lines, resonators etc., apart from the conventional capacitor applications. Similarly, work on multiferroic can be traced back to pioneering research in the 1950s and 1960s, but there has been a recent resurgence of interest driven by long-term technological aspirations. For more than a decade, BaTiO3, being a magnetic and a strong ferroelectric material at room temperature, has been renowned as a multiferroic materials that addresses a range of possible applications that no other material class exhibits so far. Out of many possible options, photovoltaic applications are being extensively considered due to the relatively low band-gap (~2.5 eV). These two material systems, BaTiO3 and BaTiO3 are widely considered as the model systems for ferroelectric and multiferroic properties and hence epitaxial thin film growth on lattice matched SrTiO3 substrates by an inexpensive hydrothermal method are considered in this thesis.One of the main requirements of producing high quality epitaxial thin films on SrTiO3 substrates is the single termination of its surface. To this effect, a novel microwave-assisted hydrothermal etching was successfully applied to the surface preparation of pure and Nb-doped BaTiO3 single crystals with (100), (110) and (111) orientations. Without the possibility of fluorine contaminations from the Teflon liner and by avoiding the etching chemistry involved with HF widely used, the surface structure appears perfect within the limitations of the in-plane and out-of-plane miscut angles. These results indicate that the utilization of this method, without any corrosive chemicals during the preparation steps, to achieve atomically flat surface with single chemical termination of BaTiO3 substrates is feasible and compatible with batch processing. This technique is inexpensive, fast, safe, environmentally benign, compatible with batch processes, and showed remarkable reproducibility. Further, this method does not need an ultra-high vacuum environment and long annealing time at high temperatures. The possibility to reduce the etching time significantly avoids the formation of etch pits and holes on the substrate surface.The hydrothermal technique is shown to be a feasible way to obtain good crystalline quality thin films of BaTiO3 and BiFeO3. This method is an inexpensive alternative technique, which is defined as any chemical reaction in presence of aqueous solvents conducted at autogenous pressure, which corresponds to the vapor pressure above room temperature and below the critical point, generally lower than 370 °C for water, in a closed system. As for the synthesis of the thin films, two hydrothermal technique modes were employed; conventional hydrothermal for BaTiO3 and microwave assisted hydrothermal for BiFeO3.

English

ISBN: 9798379462499Subjects--Topical Terms:

564049
Physics.

Hydrothermal Epitaxy of Functional Perovskite Thin Films
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520 # $a Functional oxides and their thin film epitaxy have become increasingly requested and further improvement in the existing technologies of information storage and energy harvesting heavily depends on the performance of such heterostructures at the nanoscale. Ferroelectric materials show a spontaneous electric polarization, which can be switched repeatedly by applying an external electric field. Since the discovery of ferroelectric BaTiO3 as the first oxide ferroelectric, the period prior to 1988 was mainly restricted to modelling ferroelectric phase transitions and discovering new ones. However, the focus has been significantly changed in the nineties, when thin films were developed and integrated into semiconductors at the nanoscale. This down scaling and bi-stable polarization of ferroelectrics were attractive in memory devices through ferroelectric random access memory, smart cards etc., and in tunable microwave devices through phase shifters, delay lines, resonators etc., apart from the conventional capacitor applications. Similarly, work on multiferroic can be traced back to pioneering research in the 1950s and 1960s, but there has been a recent resurgence of interest driven by long-term technological aspirations. For more than a decade, BaTiO3, being a magnetic and a strong ferroelectric material at room temperature, has been renowned as a multiferroic materials that addresses a range of possible applications that no other material class exhibits so far. Out of many possible options, photovoltaic applications are being extensively considered due to the relatively low band-gap (~2.5 eV). These two material systems, BaTiO3 and BaTiO3 are widely considered as the model systems for ferroelectric and multiferroic properties and hence epitaxial thin film growth on lattice matched SrTiO3 substrates by an inexpensive hydrothermal method are considered in this thesis.One of the main requirements of producing high quality epitaxial thin films on SrTiO3 substrates is the single termination of its surface. To this effect, a novel microwave-assisted hydrothermal etching was successfully applied to the surface preparation of pure and Nb-doped BaTiO3 single crystals with (100), (110) and (111) orientations. Without the possibility of fluorine contaminations from the Teflon liner and by avoiding the etching chemistry involved with HF widely used, the surface structure appears perfect within the limitations of the in-plane and out-of-plane miscut angles. These results indicate that the utilization of this method, without any corrosive chemicals during the preparation steps, to achieve atomically flat surface with single chemical termination of BaTiO3 substrates is feasible and compatible with batch processing. This technique is inexpensive, fast, safe, environmentally benign, compatible with batch processes, and showed remarkable reproducibility. Further, this method does not need an ultra-high vacuum environment and long annealing time at high temperatures. The possibility to reduce the etching time significantly avoids the formation of etch pits and holes on the substrate surface.The hydrothermal technique is shown to be a feasible way to obtain good crystalline quality thin films of BaTiO3 and BiFeO3. This method is an inexpensive alternative technique, which is defined as any chemical reaction in presence of aqueous solvents conducted at autogenous pressure, which corresponds to the vapor pressure above room temperature and below the critical point, generally lower than 370 °C for water, in a closed system. As for the synthesis of the thin films, two hydrothermal technique modes were employed; conventional hydrothermal for BaTiO3 and microwave assisted hydrothermal for BiFeO3.
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650 # 4 $a Point defects. $3 1372701
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