62 research outputs found
Superconducting Diode Effect and Large Magnetochiral Anisotropy in T-MoTe Thin Film
In the absence of time-reversal invariance, metals without inversion symmetry
may exhibit nonreciprocal charge transport -- a magnetochiral anisotropy that
manifests as unequal electrical resistance for opposite current flow
directions. If superconductivity also sets in, the charge transmission may
become dissipationless in one direction while remaining dissipative in the
opposite, thereby realizing a superconducting diode. Through both
direct-current and alternating-current measurements, we study the nonreciprocal
effects in thin films of the noncentrosymmetric superconductor
T-MoTe\textsubscript{2} with disorders. We observe nonreciprocal
superconducting critical currents with a diode efficiency close to 20\%~, and a
large magnetochiral anisotropy coefficient up to
\SI{5.9e8}{\per\tesla\per\ampere}, under weak out-of-plane magnetic field in
the millitesla range. The great enhancement of rectification efficiency under
out-of-plane magnetic field is likely abscribed to the vortex ratchet effect,
which naturally appears in the noncentrosymmetric superconductor with
disorders. Intriguingly, unlike the finding in Rashba systems, the strongest
in-plane nonreciprocal effect does not occur when the field is perpendicular to
the current flow direction. We develop a phenomenological theory to demonstrate
that this peculiar behavior can be attributed to the asymmetric structure of
spin-orbit coupling in T-MoTe\textsubscript{2}. Our study highlights how
the crystallographic symmetry critically impacts the nonreciprocal transport,
and would further advance the research for designing the superconducting diode
with the best performance.Comment: 7 pages, 5figure
Photoflexoelectric effect in halide perovskites
Harvesting environmental energy to generate electricity is a key scientific and technological endeavour of our time. Photovoltaic conversion and electromechanical transduction are two common energy-harvesting mechanisms based on, respectively, semiconducting junctions and piezoelectric insulators. However, the different material families on which these transduction phenomena are based complicate their integration into single devices. Here we demonstrate that halide perovskites, a family of highly efficient photovoltaic materials, display a photoflexoelectric effect whereby, under a combination of illumination and oscillation driven by a piezoelectric actuator, they generate orders of magnitude higher flexoelectricity than in the dark. We also show that photoflexoelectricity is not exclusive to halides but a general property of semiconductors that potentially enables simultaneous electromechanical and photovoltaic transduction and harvesting in unison from multiple energy inputs
A broad-spectrum gas sensor based on correlated two-dimensional electron gas
Designing a broad-spectrum gas sensor capable of identifying gas components in complex environments, such as mixed atmospheres or extreme temperatures, is a significant concern for various technologies, including energy, geological science, and planetary exploration. The main challenge lies in finding materials that exhibit high chemical stability and wide working temperature range. Materials that amplify signals through non-chemical methods could open up new sensing avenues. Here, we present the discovery of a broad-spectrum gas sensor utilizing correlated two-dimensional electron gas at a delta-doped LaAlO3/SrTiO3 interface with LaFeO3. Our study reveals that a back-gating on this two-dimensional electron gas can induce a non-volatile metal to insulator transition, which consequently can activate the two-dimensional electron gas to sensitively and quantitatively probe very broad gas species, no matter whether they are polar, non-polar, or inert gases. Different gas species cause resistance change at their sublimation or boiling temperature and a well-defined phase transition angle can quantitatively determine their partial pressures. Such unique correlated two-dimensional electron gas sensor is not affected by gas mixtures and maintains a wide operating temperature range. Furthermore, its readout is a simple measurement of electric resistance change, thus providing a very low-cost and high-efficient broad-spectrum sensing technique.</p
A sensor with coating Pt/WO3 powder with an Erbium-doped fiber amplifier to detect the hydrogen concentration
A highly sensitive hydrogen sensor coated with Pt/WO3 powder with an Erbium-doped fibre amplifier (EDFA) is proposed and experimentally demonstrated. The sensing head is constructed by splicing a short section of tapered small diameter coreless fiber (TSDCF diameter of 62.5 μm, and tapered to 14.5 μm) between two single-mode fibres. The Pt/WO3 powder adheres to the surface of PDMS film coated on the TSDCF structure, which is sensitive to hydrogen. An EDFA is introduced into the sensor system to improve the quality factor of the output spectrum and thus improve the sensor’s resolution. As the hydrogen concentration varies from 0 to 1.44, the measured maximum light intensity variation and the sensor’s sensitivity are -32.41 dB and -21.25 dB/, respectively. The sensor demonstrates good stability with the light intensity fluctuation of < 1.26 dB over a 30-minute duration
Motivation, performance and job satisfaction of construction management professionals (CMPs)
Bibliography: p. 166-175The research investigated how motivation, work experience, and education affect the performance of construction management professionals (herein after called "C:MPs") and examined the relationship between CMPs' job satisfaction and satisfaction degree of job outcomes. The job outcomes, which have significant influences on CMPs' job satisfaction, were also identified. Furthermore, the research investigated the CMPs' patterns of attitudes and satisfaction degrees toward different job outcomes according to different demographic groups. Finally, the job outcomes, which have potential problems in satisfying CMPs' needs, were identified. The findings of this research will enrich the research field of CMPs' motivation issues. The information provided by this research can assist construction companies establish efficient motivation environment to enhance CMPs' performance and job satisfaction
High throughput secondary electron imaging of organic residues on a graphene surface.
Surface organic residues inhibit the extraordinary electronic properties of graphene, hindering the development of graphene electronics. However, fundamental understanding of the residue morphology is still absent due to a lack of high-throughput and high-resolution surface characterization methods. Here, we demonstrate that secondary electron (SE) imaging in the scanning electron microscope (SEM) and helium ion microscope (HIM) can provide sub-nanometer information of a graphene surface and reveal the morphology of surface contaminants. Nanoscale polymethyl methacrylate (PMMA) residues are visible in the SE imaging, but their contrast, i.e. the apparent lateral dimension, varies with the imaging conditions. We have demonstrated a quantitative approach to readily obtain the physical size of the surface features regardless of the contrast variation. The fidelity of SE imaging is ultimately determined by the probe size of the primary beam. HIM is thus evaluated to be a superior SE imaging technique in terms of surface sensitivity and image fidelity. A highly efficient method to reveal the residues on a graphene surface has therefore been established
Helium ion microscopy for graphene characterization and modification
© 2015 by Taylor & Francis Group, LLC. The helium ion microscope (HIM) is a recently developed complementary tool to electron microscopes (Morgan et al., 2006, Ward et al., 2006, 2007, Notte et al., 2007, Postek et al., 2007b, Ananth et al., 2008, Postek and Vladar, 2008, Scipioni, 2008, Scipioni et al., 2008) and has great potential to play a crucial role in advanced material characterization and modification (Joy et al., 2007, Postek et al., 2007a, Postek and Vladar, 2008, Jepson et al., 2009a, b). The advantage and benefit of using the HIM as a high-resolution imaging tool have been demonstrated, which is expected to particularly address challenges encountered in nanoscale metrology. The invasiveness of the observation also arouses scientists’ concern, especially for fairly sensitive samples like graphene. Nevertheless, a destructive method for a confined scale characterization, on the other hand, may uncover potential for precise modification: the HIM has a demonstrated capacity to directly and accurately tailor nanostructures
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