Ferroelectricity of Nanometer-thick Bilayer Thin Films of Zirconia and Hafnia
Date Issued
2016
Date
2016
Author(s)
Lu, Yu-Wei
Abstract
Recently, HfO2-based system was reported to have ferroelectricity. Doped-HfO2, binary Hf1-xZrxO2 and undoped-HfO2 film on TiN electrode have ferroelectricity in particular experimental condition. The high-pressure orthorhombic phase having noncntrosymmetric Pbc21 space group, which is induced by encapsulation of TiN electrode, has been claimed as the origin of ferroelectricity in HfO2. Although simple application based on ferroelectric HfO2-based system has been made, the mechanism forming ferroelectric HfO2 is not fully understood. In the present study, ferroelectric characteristics of ZrO2, HfO2, and bilayer ZrO2/HfO2 film fabricated by ALD on Pt/Ti/SiO2/Si substrate has been measured and determined in this study. The mechanism by which ZrO2 and HfO2 form a ferroelectric phase and the factors influencing the phase transition are explained by combining the results of structural information, characteristic hysteresis loop, chemical analysis and phase diagram. With knowing the mechanism forming ferroelectric HfO2 and antiferroelectric ZrO2, it is believed that the two material systems have potential to be used as new lead-free ferroelectric material in near future.
Subjects
Hafnia
Zirconia
Ferroelectricity
Bilayer thin films
Type
thesis
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