Ferroelectric Devices

Kenji Uchino

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9781351834278
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Optics & Light

Updating its bestselling predecessor, Ferroelectric Devices, Second Edition assesses the last decade of developments—and setbacks—in the commercialization of ferroelectricity. Field pioneer and esteemed author Uchino provides insight into why this relatively nascent and interdisciplinary process has failed so far without a systematic accumulation of fundamental knowledge regarding materials and device development.

Filling the informational void, this collection of information reviews state-of-the-art research and development trends reflecting nano and optical technologies, environmental regulation, and alternative energy sources. Like the first edition, which became a standard in the field, this volume provides a general introduction to ferroelectrics with theoretical background. It then addresses practical design and device manufacturing, including recently developed processes and applications. Updating old data with a forecast of future developments, the text analyzes improvements to original ferroelectric devices to aid the design process of new ones.

The second edition includes new sections on:

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• Pb-free piezoelectrics

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• Size effect on ferroelectricity

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• Electrocaloric devices

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• Micro mass sensor

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• Piezoelectric energy harvesting

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• Light valves and scanners

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• Multi-ferroic devices, including magneto-electric sensors

Uchino provides a general introduction to the theoretical background of ferroelectric devices, practical materials, device designs, drive/control techniques, and typical applications. He presents frequently asked questions from students, lab demonstrations for practical understanding, and "check point" quizzes and model solutions to monitor understanding.

After a thorough exploration of ferroelectric devices and their past, this book looks to the industry's future, assessing market size and remaining reliability/lifetime issues. The author also unveils his strategy for developing "best-selling" ferroelectric devices.

1	General View of Ferroelectrics

Let us start with the “smartness” of a material. Table 1.1 lists the various effects relating the input (electric field, magnetic field, stress, heat, and light) with the output (charge/current, magnetization, strain, temperature, and light). Conducting and elastic materials, which generate current and strain outputs, respectively, for the input voltage or stress (well-known phenomena), are sometimes called “trivial” materials. On the other hand, pyroelectric and piezoelectric materials, which generate an electric field with the input of heat and stress (unexpected phenomena), respectively, are called “smart” materials. These off-diagonal couplings have corresponding converse effects, the electrocaloric and converse piezoelectric effects, and both “sensing” and “actuating” functions can be realized in the same materials. “Intelligent” materials must possess a “drive/control” or “processing” function which is adaptive to changes in environmental conditions, in addition to actuator and sensing functions. Ferroelectric materials exhibit most of these effects with the exception of the magnetic phenomena. Thus, ferroelectrics are said to be very “smart” materials.

Ferroelectrics are utilized in various devices such as high-permittivity dielectrics, pyroelectric sensors, piezoelectric devices, electro-optic devices, and positive temperature coefficient (PTC) of resistivity components. However, ferroelectric devices often fail to be commercialized in areas of application where competitive materials exist. Light sensors, for example, typically are manufactured from semi-conductive materials which are superior to ferroelectrics in response speed and sensitivity. Magnetic devices are much more popular for memory applications, and liquid crystals are typically used for optical displays. One reason for this is due to the lack of systematic and comprehensive compilation of knowledge on ferroelectric materials. In this chapter, we will learn the fundamentals of ferroelectricity.

1.1 CRYSTAL STRUCTURE AND FERROELECTRICITY

In the so-called dielectric materials, the constituent atoms are considered to be ionized to a certain degree and are either positively or negatively charged. In such ionic crystals, when an electric field is applied, cations are attracted to the cathode and anions to the anode due to electrostatic interaction. The electron clouds also deform, causing electric dipoles. This phenomenon is known as electric polarization of the dielectric, and the polarization is expressed quantitatively as the sum of the electric dipoles per unit volume (C/m²). Figure 1.1 shows schematically the origin of the electric polarization. There are three primary contributions: electronic, ionic, and dipole reorientation-related. The degree ...