http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Shedding light on nanoscale ferroelectrics
Jan Seidel,Lukas M. Eng 한국물리학회 2014 Current Applied Physics Vol.14 No.8
Light matter interactions in nanoscale ferroelectric materials have received growing interest over the last years due to new developments in scientific instrumentation and novel materials that allow for the study of so far scarcely investigated and/or hidden nanoscale phenomena. Here we provide an overview of these developments and investigations that have been carried out over a broad range of frequencies spanning from the X-ray to the THz regime. Of interest are the physical quantities and fingerprints stemming from nanoscale regions in ferroelectrics, including domain walls, upon light illumination.
Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO3 thin films
Heo, Yooun,Hong Lee, Jin,Xie, Lin,Pan, Xiaoqing,Yang, Chan-Ho,Seidel, Jan Nature Publishing Group 2016 NPG Asia Materials Vol.8 No.-
<P>Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic-rhombohedral (O-R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phases using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R-O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Therefore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.</P>
Doping BiFeO<sub>3</sub>: approaches and enhanced functionality
Yang, Chan-Ho,Kan, Daisuke,Takeuchi, Ichiro,Nagarajan, Valanoor,Seidel, Jan The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.46
<P>BiFeO<SUB>3</SUB> is one of the most studied multiferroic materials. Both its magnetic and ferroelectric properties can be influenced by doping. A large body of work on the doped material has been presented in the past couple of years. In this paper we provide a perspective on general doping concepts and their impact on the material's functionality.</P> <P>Graphic Abstract</P><P>This paper provides a perspective on general doping concepts of multiferroic BiFeO<SUB>3</SUB> and their impact on the material's functionality. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp43082g'> </P>
Out-of-plane three-stable-state ferroelectric switching: Finding the missing middle states
Lee, Jin Hong,Chu, Kanghyun,Kim, Kwang-Eun,Seidel, Jan,Yang, Chan-Ho American Physical Society 2016 Physical Review B Vol.93 No.11
<P>By realizing a nonvolatile third intermediate ferroelectric state through anisotropicmisfit strain, we demonstrate electrical switching among three stable out-of-plane polarizations in bismuth ferrite thin films grown on (110)(pc)-oriented gadolinium scandate substrates (where pc stands for pseudocubic) by the use of an asymmetric external electric field at the step edge of a bottom electrode. We employ phenomenological Landau theory, in conjunction with electrical poling experiments using piezoresponse force microscopy, to understand the role of anisotropic misfit strain and an in-plane electric field in stabilization of multiple ferroelectric states and their competition. Our finding provides a useful insight into multistep ferroelectric switching in rhombohedral ferroelectrics.</P>
신소정,안명현,김진철,김문용,Ghaida Alosaimi,김도형,하나영,Jan Seidel,박노창,윤재성,김종현 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
In this work, we report on the design principles of high-power perovskite solar cells (PSCs) for low-intensity indoor light applications, with a particular focus on the electron transport layers (ETLs). It was found that the mechanism of power generation of PSCs under low-intensity LED and halogen lights is surprisingly different compared to the 1 Sun standard test condition (STC). Based on the systemic characterization of the ideality factor, charge recombination, trap density, and charge-separation, it was revealed that interfacial charge traps or defects at the electron transport layer/perovskite have a critical impact on the resulting power density of PSC under weak light conditions. Thus, using the suggested principle, we succeeded in demonstrating high-performance PSCs by employing an organic ETL, yielding maximum power densities.
Impact of Isovalent and Aliovalent Doping on Mechanical Properties of Mixed Phase BiFeO<sub>3</sub>
Heo, Yooun,Hu, Songbai,Sharma, Pankaj,Kim, Kwang-Eun,Jang, Byung-Kweon,Cazorla, Claudio,Yang, Chan-Ho,Seidel, Jan American Chemical Society 2017 ACS NANO Vol.11 No.3
<P>In this study, we report the effect of doping in morphotropic BiFeO3 (BFO) thin films on mechanical properties, revealing variations in the elasticity across the competing phases and their boundaries. Spectroscopic force-distance (F-D) curves and force mapping images by AFM are used to characterize the structure and elastic properties of three BFO thin-film candidates (pure-BFO, Ca-doped BFO, La-doped BFO). We show that softening behavior is observed in isovalent La-doped BFO, whereas hardening is seen in aliovalent Ca-doped BFO. Furthermore, quantitative F-D measurements are extended to show threshold strengths for phase transitions, revealing their dependence on doping in the system. First-principles simulation methods are also employed to understand the observed mechanical properties in pure and doped BFO thin films and to provide microscopic insight on them. These results provide key insight into doping as an effective control parameter to tune nanomechanical properties and suggest an alternative framework to control coupled ferroic functionalities at the nanoscale.</P>