Browsing by Author "Zhong, Chaorong"

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Electrical polarization induced by atomically engineered compositional gradient in complex oxide solid solution
(2019-04-12)
Wu, Ping-Chun
;
Huang, Rong
;
Hsieh, Ying-Hui
;
Wang, Bo
;
Yen, Min
Control of inhomogeneity in materials in order to avoid unexpected effects to the system remains a challenge. In this study, we seek to engineer inhomogeneity in materials and anticipate new properties. Through precise control of composition at the atomic scale, an electrical polarization is induced in the composition-graded LaAIO(3)-SrTiO3 solid solution epitaxially deposited on NdGaO3 substrates. By tailoring the direction of compositional gradient, the relationship between structure and electrical polarization is simulated via phase-field modeling and revealed by a combination of scanning transmission electron microscopy and scanning probe microscopy. The analysis of the results indicates that the induced polarization is due to the flexoelectric effect in the compositional gradient system. The results of this study provide a new pathway for obtaining a new material genome. Moreover, by a suitable design of the new genome, that is, by using different combinations of compositional gradient geometries, local conduction can be obtained and manipulated, providing a new approach to obtain the desired properties.
High Mobilities in Layered InSe Transistors with Indium-Encapsulation-Induced Surface Charge Doping
(2018-11-02)
Li, Mengjiao
;
Lin, Che-Yi
;
Yang, Shih-Hsien
;
Chang, Yuan-Ming
;
Chang, Jen-Kuei
Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field-effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm(2) V-1 s(-1) at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron-doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low-frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature-dependent mobility. Finally, the flexible functionalities of the logic-circuit applications, for instance, inverter and not-and (NAND)/not-or (NOR) gates, are determined with these surface-doping InSe FETs, which establish a paradigm for 2D-based materials to overcome the bottleneck in the development of electronic devices.