• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.330-342
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• 2020

Since the original report on ferroelectricity in Si-doped HfO2 in 2011, fluorite-structured ferroelectrics have attracted increasing interest due to their scalability, established deposition techniques including atomic layer deposition, and compatibility with the complementary-metal-oxide-semiconductor technology. Especially, the emerging fluorite-structured ferroelectrics are considered promising for the next-generation semiconductor devices such as storage class memories, memory-logic hybrid devices, and neuromorphic computing devices. For achieving the practical semiconductor devices, understanding polarization switching kinetics in fluorite-structured ferroelectrics is an urgent task. To understand the polarization switching kinetics and domain dynamics in this emerging ferroelectric materials, various classical models such as Kolmogorov-Avrami-Ishibashi model, nucleation limited switching model, inhomogeneous field mechanism model, and Du-Chen model have been applied to the fluorite-structured ferroelectrics. However, the polarization switching kinetics of fluorite-structured ferroelectrics are reported to be strongly affected by various nonideal factors such as nanoscale polymorphism, strong effect of defects such as oxygen vacancies and residual impurities, and polycrystallinity with a weak texture. Moreover, some important parameters for polarization switching kinetics and domain dynamics including activation field, domain wall velocity, and switching time distribution have been reported quantitatively different from conventional ferroelectrics such as perovskite-structured ferroelectrics. In this focused review, therefore, the polarization switching kinetics of fluorite-structured ferroelectrics are comprehensively reviewed based on the available literature.

• Journal of the Korean institute of surface engineering
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• v.53 no.4
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• pp.169-181
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• 2020

The ferroelectricity in emerging fluorite-structure oxides such as HfO₂ and ZrO₂ has attracted increasing interest since 2011. Different from conventional ferroelectrics, the fluorite-structure ferroelectrics could be reliably scaled down below 10 nm thickness with established atomic layer deposition technique. However, defects such as carbon, hydrogen, and nitrogen atoms in fluorite-structure ferroelectrics are reported to strongly affect the nanoscale polymorphism and resulting ferroelectricity. The characteristic nanoscale polymorphism and resulting ferroelectricity in fluorite-structure oxides have been reported to be influenced by defect concentration. Moreover, the conduction of charge carriers through fluorite-structure ferroelectrics is affected by impurities. In this review, the origin and effects of various kinds of defects are reviewed based on existing literature.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.480-488
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• 2020

The electrocaloric effect can be observed in pyroelectric materials based on conversion between electrical and thermal energy, and can be utilized for the future environment-friendly refrigeration technology. Especially, a strong electrocaloric effect is expected in materials in which field-induced phase transition can be achieved. Emerging fluorite-structure ferroelectrics such as doped hafnia and zirconia, first discovered in 2011, are considered the most promising materials for next-generation semiconductor devices. Besides application of fluorite-structure ferroelectrics for semiconductor devices based on their scalability and CMOS-compatibility, field-induced phase transition has been suggested as another interesting phenomenon for various energy-related applications such as solid-state cooling with electrocaloric effect as well as energy conversion/storage and IR/piezoelectric sensors. Especially, their giant electrocaloric effect is considered promising for solid-state-cooling. However, the electrocaloric effect of fluorite-structure oxides based on field-induced phase transition has not been reviewed to date. In this review, therefore, the electrocaloric effect accompanied by field-induced phase transition in fluorite-structure ferroelectrics is comprehensively reviewed from fundamentals to potential applications.

• Journal of the Korean Ceramic Society
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• v.38 no.7
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• pp.667-671
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• 2001

Sawyer-tower 회로를 이용한 강유전 이력곡선의 측정과정에서의 주요 오차 원인을 살펴보고 이에 대한 대안을 제시해 보았다. 강유전체 시편에 존재하는 직류 누설성분에 의해 잔류분극과 항전계는 과대평가될 수 있는 위험성이 항상 있음을 알 수 있었으며 이러한 오차의 보정에 대하여 논의하였다. 또한 강유전 이력곡선의 측정에서 측정하는 시간이 증가되면서 시편의 발열로 인해서 시편의 온도가 증가하게 되어 잔류분극 값과 항전계 값이 감소하는 경향으로 나타남을 관찰하였고, 그 대책을 제안하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.562-566
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• 2001

The effects of MnO$_2$ addition on the properties in Pb(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ relaxor ferroelectrics were studied in the phase transition temperature range from -4$0^{\circ}C$ to 11$0^{\circ}C$. Specimens were made via solid state processing method. Dielectric properties, piezoelctric properties, electric-field-induced strain were examined to clarify the effect of MnO$_2$ addition in 0.9MN-0.1PT. As the amount of MnO$_2$ increases, the maximum dielectric constant and the dielectric loss decreases. Q$_{m}$ increased by increasing the doping contents of Mn. When 0.5wt% MnO$_2$ was doped, Q$_{m}$ increased from 95 to 480. The electric-filed-induced strain and polarization decreases as the amount of MnO$_2$ increases. From the experimental results, it was suggested that Mn behaves as an ferroelectric domain pinning element.ent.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.99-104
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• 2020

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO₂) have led to the expectation that HfO₂ could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO₂ thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO₂-based MFM capacitors by applying various ferroelectric switching characteristics models.

• Journal of the Korean institute of surface engineering
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• v.55 no.5
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• pp.247-260
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• 2022

Since the first report on ferroelectricity in Si-doped hafnia (HfO2), this emerging ferroelectrics have been considered promising for the next-generation semiconductor devices with their characteristic nonvolatile data storage. The robust ferroelectricity in the sub-10-nm thickness regime has been proven by numerous research groups. However, extending their scalability below the 5 nm thickness with low temperature processes compatible with the back-end-of-line technology. In this review, therefore, the current status, technical issues, and their potential solutions of atomic layer deposition (ALD) of HfO₂-based ferroelectrics are comprehensively reviewed. Several technical issues in the physical scaling of the ferroelectric thin films and potential solutions including advanced ALD techniques including discrete feeding ALD, atomic layer etching, and area selective ALD are introduced.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.109.2-109.2
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• 2007

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.157-161
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• 2001

The observe relaxation phenomena and freezing behavior in Pb(Mg/sub ⅓/Nb/sub ⅔/O₃, relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated. The temperature dependence of the dielectric properties obtained using the low electric-field of 1 V/w was investigated. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Filcher relation, a close agreement between the experimental data and equation was observed. The freezing temperature could be consistently calculated by the various methods.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1206-1210
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• 2003

Effect of transverse electric field on crack kinking in ferroelectric ceramics subjected to purely electric loading is investigated. It is shown that the shape and size of the domain switching zone depends strongly on the direction of the applied electric field as well as the ratio of the transverse electric field to the coercive electric field. Under small-scale conditions, mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectrics is also discussed.