Supervisor’s Foreword As an important ferroelectric material, Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) solid solutions combined the advantages of relaxor ferroelectric PMN and ferroelectric PT predictably. With the modi?ed Bridgman technique, large-size and high-quality PMN-PT single crystals have been successfully grown. The single crystals with the composition near the morphotropic phase boundary (MPB) exhibit ultra high piezoelectric constant of *2500 pC/N and large electromechanical coupling coef?cient up to 0.9. In recent years, piezoelectric devices based on the PMN-PT single crystals have received much attention and made a revolution in the elec- tromechanical transduction area. In contrast, the applications related to their excellent ferroelectric and pyroelectric properties of this multifunctional materials are still not mature enough. Therefore, further investigation on extending their ferroelectric and pyroelectric applications is highly desirable. 　The main aim of this doctoral thesis is to explore the applications of ferroelectric materials such as PMN-PT single crystals in information technology. Several prototype devices have been designed and fabricated which are responsible for the collection, processing and storage of the information data. For example, an optothermal ?eld effect transistor (FET) based on the pyroelectric PMN-PT single crystal and MoS2 single-layer ?lm is introduced in Chap. 2. Infrared light can be used as the input signal instead of the gate voltage to realize remote controlling of the channel current. In Chap. 3, a new photodetector with ultra-wide spectral response in the ultraviolet to terahertz band has been achieved by using the high pyroelectric coef?cient of PMN-PT single crystals. The detecting performance is improved through domain engineering and structural optimization of the device. To use the mechanical energy in the environment as the energy source for information writing, a self-powered ferroelectric memory system is demonstrated in Chap. 4. The data can be written in the PMN-PT-based FET by tapping a triboelectric nanogenerator. 　The research was carried out at Department of Chemistry in Tsinghua University with the cooperation from Department of Applied Physics in The Hong Kong Polytechnic University, Department of Physics in Tsinghua University and Institute of Microelectronics in Tsinghua University. The research contents in this thesis are VIII Supervisor’s Foreword not only in the frontiers of ferroelectric materials, but also at the multidisciplinary highly cross-cutting edge. Some excited results and design ideas are expected to drive ferroelectric materials to play an important role in a wide range of applications. Beijing, China Assoc. Prof. Qingfeng Yan January 2020

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