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Huami Liang - One of the best experts on this subject based on the ideXlab platform.
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surface plasmon resonance instrument as a refractometer for liquids and Ultrathin Films
Sensors and Actuators B-chemical, 2010Co-Authors: Huami Liang, Heini Miranto, Niko Granqvis, Janusz W Sadowski, Tapani Viitala, Ochu Wang, Marjo YliperttulaAbstract:Abstract A surface plasmon resonance (SPR) setup in Kretschmann configuration is being utilized as a refractometer for both liquids as well as Ultrathin Films. The SPR signal detection technology used is based on a goniometer approach providing a wide angular scan range which facilitates highly accurate liquid and gas phase measurements. Attention was paid to improve sample handling and preparation. In order to avoid cross-contamination between measurements an easily removable and exchangeable molded PDMS flow cell was used during the measurements. By careful choice of components for liquid handling the dead volume of the system could be reduced down to some microliters. The angular change and thus the refractive index for sucrose, ethylene glycol (EG) and ethanol solutions with different concentrations, the thickness and refractive index of deposited Langmuir-Blodgett (LB) Films, and the interaction kinetics between a biotin containing self-assembled monolayer (SAM) and streptavidin were determined. The measured refractive indices of sucrose, EG and ethanol solutions corresponded well with literature values. LB Films were characterized by measuring the complete SPR curve in an angular scan range from 40 to 78°. A two-color SPR approach combined with two-media measurements was successfully employed for simultaneous and unambiguous determination of both refractive index and thickness of stearic acid monolayers. The thickness obtained for the stearic acid monolayer was 2.66 nm, and the refractive indices at 635 and 670 nm were 1.5800 and 1.4138, respectively. The developed sensor-plate holder enabled functionalization of the SPR gold chip outside the instrument, therefore making the sample handling more flexible. The affinity constant obtained for the streptavidin–biotin interaction was 1.01 × 10 −8 M. The total angle SPR method used in this study clearly shows its potential to be used as a refractometer for both liquids and Ultrathin Films, as well as for traditional liquid phase biomolecular kinetic studies.
Avner Rothschild - One of the best experts on this subject based on the ideXlab platform.
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resonant light trapping in Ultrathin Films for water splitting
Nature Materials, 2013Co-Authors: Hen Dotan, Ofer Kfir, Elad Sharlin, Oshri Blank, Moran Gross, Irina Dumchin, Guy Ankonina, Avner RothschildAbstract:Semiconductor photoelectrodes for solar hydrogen production by water photoelectrolysis require stable and abundant visible-light absorbers such as iron oxide. Although this material suffers from poor transport properties for efficient charge-carrier generation and collection, these drawbacks can now be addressed by using resonant light trapping in Ultrathin Films designed as optical cavities.
L. Bellaiche - One of the best experts on this subject based on the ideXlab platform.
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Diffuse phase transitions in ferroelectric Ultrathin Films from first principles
Physical Review B: Condensed Matter and Materials Physics, 2010Co-Authors: S. Bin-omran, I. Kornev, I. Ponomarev, L. BellaicheAbstract:A first-principles-derived scheme is developed and used to investigate the diffuse character of the paraelectric-to-ferroelectric transition in Ultrathin Films made of BaTiO3, and to reveal its dependency on mechanical and electrical boundary conditions, as well as on thickness. It is found that such diffuse character does not require the presence of defects to occur, unlike commonly believed, but rather can originate from surface-induced dipolar inhomogeneities in defect-free Films.
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Domain evolution of BaTi O3 Ultrathin Films under an electric field A first-principles study
Physical Review B: Condensed Matter and Materials Physics, 2007Co-Authors: B.-k. Lai, I. Ponomareva, I.a. Kornev, L. Bellaiche, G.j. SalamoAbstract:A first-principles-derived method is used to study the morphology and electric-field-induced evolution of stripe nanodomains in (001) BaTi O3 (BTO) Ultrathin Films, and to compare them with those in (001) Pb (Zr,Ti) O3 (PZT) Ultrathin Films. The BaTi O3 systems exhibit 180° periodic stripe domains at null electric field, as in PZT Ultrathin Films. However, the stripes alternate along [1-10] in BTO systems versus [010] in PZT systems, and no in-plane surface dipoles occur in BTO Ultrathin Films (unlike in PZT materials). Moreover, the evolution of the 180° stripe domains in the BaTi O3 systems, when applying and increasing an electric field along [001], involves four regions region I for which the magnitude of the "down" dipoles (i.e., those that are antiparallel to the electric field) is reduced, while the domain walls do not move; region II in which some local down dipoles adjacent to domain walls switch their direction, resulting in zigzagged domain walls-with the overall stripe periodicity being unchanged; region III in which nanobubbles are created, then contract along [110] and finally collapse; and region IV which is associated with a single monodomain. Such evolution differs from that of PZT Ultrathin Films for which neither region I nor zigzagged domain walls exist, and for which the bubbles contract along [100]. Discussion about such differences is provided. © 2007 The American Physical Society.
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Properties of ferroelectric Ultrathin Films from first principles
2007Co-Authors: I.a. Kornev, L. BellaicheAbstract:Advances in first-principles computational approaches have, over the past ten years, made possible the investigation of basic physical properties of simple ferroelectric systems. Recently, first-principles techniques also proved to be powerful methods for predicting finite-temperature properties of solid solutions in great details. Consequently, bulk perovskites are rather well understood nowadays. On the other hand, one task still remains to be accomplished by ab-initio methods, that is, an accurate description and a deep understanding of ferroelectric nanostructures. Despite the fact that nanometer scale ferroelectric materials have gained widespread interest both technologically and scientifically (partly because of novel effects arising in connection with the reduction of their spatial extension), first-principles- based calculations on ferroelectric nanostructures are rather scarce. For instance, the precise effects of the substrate, growth orientation, surface termination, boundary conditions and thickness on the finite-temperature ferroelectric properties of Ultrathin Films are not well established, since their full understandings require (i) microscopic insights on nanoscale behavior that are quite difficult to access and analyze via experimental probes, and (ii) the development of new computational schemes. One may also wonder how some striking features exhibited by some bulk materials evolve in the corresponding thin Films. A typical example of such feature is the morphotropic phase boundary of various solid solutions, where unusual low-symmetry phases associated with a composition-induced rotation of the spontaneous polarization and an enhancement of dielectric and piezoelectric responses were recently discovered. In this paper, recent findings resulting from the development and use of numerical first-principles-based tools on ferroelectric Ultrathin Films are discussed © 2007 Springer Science+Business Media LLC.
Douglas Mills - One of the best experts on this subject based on the ideXlab platform.
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extrinsic contributions to the ferromagnetic resonance response of Ultrathin Films
Physical Review B, 1999Co-Authors: Rodrigo Arias, Douglas MillsAbstract:We develop a theory of the extrinsic contributions to the ferromagnetic resonance linewidth and frequency shift of Ultrathin Films. The basic mechanism is two magnon scattering by defects at surfaces and interfaces. In the presence of dipolar couplings between spins in the film, one realizes short wavelength spin waves degenerate with the ferromagnetic resonance (FMR) mode, provided the magnetization is parallel to the film surfaces. Defects on the surface or interface thus scatter the FMR mode into such short wavelength spin waves, producing a dephasing contribution to the linewidth, and a frequency shift of the resonance field. The mechanism described here is inoperative when the magnetization is perpendicular to the film.
S P Lau - One of the best experts on this subject based on the ideXlab platform.
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field effect transistors based on amorphous black phosphorus Ultrathin Films by pulsed laser deposition
Advanced Materials, 2015Co-Authors: Zhibin Yang, Jianhua Hao, Shuoguo Yuan, Shenghuang Lin, Hei Man Yau, Jiyan Dai, S P LauAbstract:Amorphous black phosphorus (a-BP) Ultrathin Films are deposited by pulsed laser deposition. a-BP field-effect trans-istors, exhibiting high carrier mobility and moderate on/off current ratio, are demonstrated. Thickness dependence of the bandgap, mobility, and on/off ratio are observed. These results offer not only a new nanoscale member in the BP family, but also a new opportunity to develop nano-electronic devices.