AC bolometer theory is built on the established matrix formalism for quantum calorimeters and bolometers. The bolometer is represented by a 3
×
3 matrix with complex valued parameters. The ...bolometer matrix is used to model the behavior of the devices including the response to signal and noise, feedback, pulse response times, stability, and bolometer impedance. The effects of a current dependent bolometer impedance are included. The matrix simplifies theoretical computations of AC devices, including demodulation and the interactions between signals at different frequencies. This theory is applied to measurements of bolometers, each consisting of a kinetic inductance device suspended on a silicon nitride membrane. These measurements and analysis facilitate the optimization of the design and performance of these novel AC bolometers.
Using a set of scanning probe microscopy techniques, we demonstrate the reproducible tunneling electroresistance effect on nanometer-thick epitaxial BaTiO3 single-crystalline thin films on SrRuO3 ...bottom electrodes. Correlation between ferroelectric and electronic transport properties is established by direct nanoscale visualization and control of polarization and tunneling current. The obtained results show a change in resistance by about 2 orders of magnitude upon polarization reversal on a lateral scale of 20 nm at room temperature. These results are promising for employing ferroelectric tunnel junctions in nonvolatile memory and logic devices.
Minor histocompatibility antigens (mHags) are polymorphic peptides presented to T lymphocytes restricted by the MHC molecule. It has been reported that disparities of mHags are a potential risk ...factor for GVHD after hematopoietic SCT (HSCT). Here we observed allelic frequencies of HA-1, -2 and -8 in 139 Korean healthy individuals using PCR-sequence-specific primers, and analyzed the correlation between disparity of these mHags and acute GVHD (aGVHD) in 54 patients who underwent HSCT from unrelated HLA-identical donors. The allelic frequencies in Korean healthy individuals were 39.6 and 60.4% for HA-1(H) and HA-1(R), 92.4 and 7.6% for HA-2(M) and HA-2(V), 36.7 and 63.3% for HA-8(R) and HA-8(P), respectively. The frequencies of mHags incompatibility known to be associated with aGVHD were 16.7% in HA-1, 0% in HA-2 and 25.9% in HA-8. However, the statistically significant association of aGVHD with these mHags incompatibility was not found between healthy donors and leukemia patients after unrelated HSCT. This first report about mHags in Koreans may be helpful in further defining the clinical impact of mHags disparities in HSCT and in comparing with other populations.
Abstract
The control of the in-plane domain evolution in ferroelectric thin films is not only critical to understanding ferroelectric phenomena but also to enabling functional device fabrication. ...However, in-plane polarized ferroelectric thin films typically exhibit complicated multi-domain states, not desirable for optoelectronic device performance. Here we report a strategy combining interfacial symmetry engineering and anisotropic strain to design single-domain, in-plane polarized ferroelectric BaTiO
3
thin films. Theoretical calculations predict the key role of the BaTiO
3
/PrScO
3
$${({{{\boldsymbol{110}}})}_{{{\bf{O}}}$$
(
110
)
O
substrate interfacial environment, where anisotropic strain, monoclinic distortions, and interfacial electrostatic potential stabilize a single-variant spontaneous polarization. A combination of scanning transmission electron microscopy, piezoresponse force microscopy, ferroelectric hysteresis loop measurements, and second harmonic generation measurements directly reveals the stabilization of the in-plane quasi-single-domain polarization state. This work offers design principles for engineering in-plane domains of ferroelectric oxide thin films, which is a prerequisite for high performance optoelectronic devices.
Multiferroics, where (anti-) ferromagnetic, ferroelectric and ferroelastic order parameters coexist, enable manipulation of magnetic ordering by an electric field through switching of the electric ...polarization. It has been shown that realization of magnetoelectric coupling in a single-phase multiferroic such as BiFeO3 requires ferroelastic (71 , 109 ) rather than ferroelectric (180 ) domain switching. However, the control of such ferroelastic switching in a single-phase system has been a significant challenge as elastic interactions tend to destabilize small switched volumes, resulting in subsequent ferroelastic back-switching at zero electric field, and thus the disappearance of non-volatile information storage. Guided by our phase-field simulations, here we report an approach to stabilize ferroelastic switching by eliminating the stress-induced instability responsible for back-switching using isolated monodomain BiFeO3 islands. This work demonstrates a critical step to control and use non-volatile magnetoelectric coupling at the nanoscale. Beyond magnetoelectric coupling, it provides a framework for exploring a route to control multiple order parameters coupled to ferroelastic order in other low-symmetry materials.
Ferroelectric Tunnel Memristor Kim, D. J; Lu, H; Ryu, S ...
Nano letters,
11/2012, Letnik:
12, Številka:
11
Journal Article
Recenzirano
Strong interest in resistive switching phenomena is driven by a possibility to develop electronic devices with novel functional properties not available in conventional systems. Bistable resistive ...devices are characterized by two resistance states that can be switched by an external voltage. Recently, memristorselectric circuit elements with continuously tunable resistive behaviorhave emerged as a new paradigm for nonvolatile memories and adaptive electronic circuit elements. Employment of memristors can radically enhance the computational power and energy efficiency of electronic systems. Most of the existing memristor prototypes involve transition metal oxide resistive layers where conductive filaments formation and/or the interface contact resistance control the memristive behavior. In this paper, we demonstrate a new type of memristor that is based on a ferroelectric tunnel junction, where the tunneling conductance can be tuned in an analogous manner by several orders of magnitude by both the amplitude and the duration of the applied voltage. The ferroelectric tunnel memristors exhibit a reversible hysteretic nonvolatile resistive switching with a resistance ratio of up to 105 % at room temperature. The observed memristive behavior is attributed to the field-induced charge redistribution at the ferroelectric/electrode interface, resulting in the modulation of the interface barrier height.
We present an optical lock-in detection scheme, called the integrating-bucket technique, as a signal-to-background ratio enhancement method for wide-field fluorescence imaging of biological cells. ...The proposed method uses sinusoidally modulated illumination light and captures four frames of fluorescence images, one per each quarter of the modulation period, by integrating the fluorescence intensity signal. The capability of this technique is demonstrated by imaging fluorescent bead solutions as well as labeled cells. The results show that the method yields a 4–10dB higher signal contrast than conventional fluorescence microscopy, and a background-free fluorescence image can be extracted within a sub-second time scale. Our findings indicate that the proposed method could be advantageous for the long-term study of live cells.
•We demonstrate a new application of the four-bucket technique for high-contrast fluorescence cell imaging.•We examine capability of four-bucket technique as a contrast enhancement method.•Fluorescence imaging with four-bucket technique shows contrast-enhanced image compared to conventional fluorescence microscopy.•Fluorescence-contrast enhancement by this kind of method will be useful in live cell imaging.
We demonstrate a novel scheme for manipulating metallic nanostructures involving a macroscopic number of atoms, yet with precise control in their local structures. The scheme entails a two-step ...process: (a) a triggering step using a scanning tunneling microscope, followed by (b) self-driven and self-limiting mass-transfer process. By using this scheme, we construct Pb nanomesas on Si(111) substrates whose thickness can be controlled with atomic-layer precision. The kinetic barrier for the mass transfer and the underlying mechanism behind this novel manipulation are determined.
Isostructural metal-insulator transition in VO2 Lee, D; Chung, B; Shi, Y ...
Science (American Association for the Advancement of Science),
11/2018, Letnik:
362, Številka:
6418
Journal Article
Recenzirano
Odprti dostop
Separating structure and electrons in VO2Above 341 kelvin—not far from room temperature—bulk vanadium dioxide (VO2) is a metal. But as soon as the material is cooled below 341 kelvin, VO2 turns into ...an insulator and, at the same time, changes its crystal structure from rutile to monoclinic. Lee et al. studied the peculiar behavior of a heterostructure consisting of a layer of VO2 placed underneath a layer of the same material that has a bit less oxygen. In the VO2 layer, the structural transition occurred at a higher temperature than the metal-insulator transition. In between those two temperatures, VO2 was a metal with a monoclinic structure—a combination that does not occur in the absence of the adjoining oxygen-poor layer.Science, this issue p. 1037The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.
We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz second harmonic emission vanishes above ...the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, THz driving frequency that is not allowed by equilibrium symmetry. We explain the microscopic physics by a dynamical symmetry breaking principle at sub-THz-cycle by using quantum kinetic modeling of the interplay between strong THz-lightwave nonlinearity and pulse propagation. The resulting nonzero integrated pulse area inside the superconductor leads to light-induced nonlinear supercurrents due to subcycle Cooper pair acceleration, in contrast to dc-biased superconductors, which can be controlled by the band structure and THz driving field below the superconducting gap.
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