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We propose and demonstrate a chiral metasurface with capability for high Q-factor, near-unity (0.999) circular dichroism (CD) via utilization of bound states in the continuum. The CD response can be reversed with the value ranging from −0.7 to 0.82 by increasing structural perturbations to induce chiral magnetic quadrupole modes and the accompanied phase jump. In addition, more than 100-fold enhancement of C/CCPL in the superchiral near field is achieved while maintaining a high Q-factor of 105. The findings hold broad application prospects in chiral sensing, valley electronics, and ultrasensitive chiral spectroscopy detection. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance force microscopy (FMRFM) is a powerful scanned probe technique that uses sub-micrometer-scale, spatially localized standing spin wave modes (LMs) to perform local ferromagnetic resonance (FMR) measurements. Here, we show the spatially resolved imaging of Gilbert damping in a ferromagnetic material (FM) using FMRFM. Typically damping is measured from the FMR linewidth. We demonstrate an approach to image the spatial variation of Gilbert damping utilizing the LM resonance peak height to measure the LM resonance cone angle. This approach enables determination of damping through field-swept FMRFM at a single excitation frequency. The extreme force sensitivity of ∼2 fN at room temperature can resolve changes of Gilbert damping as small as ∼ 2 × 10 − 4 at 2 GHz, corresponding to ∼0.16 Oe in FMR linewidth resolution. This high sensitivity, high spatial resolution, and single frequency imaging of Gilbert damping creates the opportunity to study spin interactions at the interface between an insulating FM and a small volume of nonmagnetic material such as atomically thin two-dimensional materials. [ABSTRACT FROM AUTHOR]

In this work, high-quality SnO2 and Hf0.38Sn0.62O2 thin films were grown on c-plane sapphire substrates by pulsed laser deposition for a comparative study. The optical and electrical tests show that Hf doping leads to significantly increased bandgap and resistivity of the HfSnO2 alloy as compared to SnO2. Then, SnO2- and Hf0.38Sn0.62O2-based UV detectors were fabricated and compared. The Hf0.38Sn0.62O2 film-based detector exhibits an excellent performance. Its dark current is as low as 0.2 pA under 20 V, and the rise/decay response time is as short as 69 ms/50 ms. The cut-off wavelength and the rejection ratio are 290 nm and 4100, respectively. Our work demonstrates that the Hf0.38Sn0.62O2 ternary alloy compound semiconductor has great potential for applications in solar-blind ultraviolet detections. [ABSTRACT FROM AUTHOR]

Metallic ferromagnets with ultra-low damping are highly desirable for charge-based spintronic applications. Here, we systematically investigate the magnetic dynamics of Co25Fe75 epitaxial films with a Gilbert damping constant as low as 7.1 × 10−4. The in-plane angular dependence of ferromagnetic resonance (FMR) was measured on various thicknesses of Co25Fe75 films grown on MgO and MgAl2O4, from which the mechanisms for FMR linewidth broadening can be distinguished and quantified. The thickness dependencies of the magnetic anisotropy and inhomogeneous broadening of the linewidth are good indicators of crystal quality and magnetic uniformity. Additionally, it is shown that anisotropic two-magnon scattering is induced by defects at the surfaces. [ABSTRACT FROM AUTHOR]

The authors report the initial results from a holographic lithography technique using extreme ultraviolet (EUV) radiation. This approach removes the need for complex EUV reflective masks and optics, replacing them with a binary, nanopatterned transmission mask. Computer generated holograms were fabricated on 100 nm thick silicon nitride membranes with a 100 nm thick chromium absorber layer. Reconstructed images have been recorded in an 80 nm thick polymethylmetacrylate photoresist using 13 nm wavelength EUV radiation from an undulator source. The pattern was characterized by optical and atomic force microscopies, and compared with simulation results from the TOOLSET diffraction simulation program, yielding excellent agreement. [ABSTRACT FROM AUTHOR]

The microscopic superelastic behavior of a nickel-titanium (NiTi) alloy has been studied by instrumented indentation experiments using both spherical and pyramidal (e.g., Berkovich) diamond indenters. The indentation load-displacement curves for a superelastic NiTi and an annealed copper were obtained under a range of indentation conditions. We show that indentation-induced superelasticity exists under both spherical and pyramidal indenters, which may be exploited for many applications, ranging from microelectromechanical systems to surface engineering. [ABSTRACT FROM AUTHOR]

We report a method of making nanowires of bismuth (Bi) with diameters ranging from 30 to 200 nm and lengths up to several millimeters. The nanowires are extruded spontaneously at the rate of a few micrometers per second at room temperature from the surfaces of freshly grown composite thin films consisting of Bi and chrome-nitride. The high compressive stress in these composite thin films is the driving force responsible for the nanowire formation. This mechanism can also be used to create nanowires of other materials. [ABSTRACT FROM AUTHOR]

The thermally induced recovery of microscopic deformation in a nickel-titanium shape-memory alloy was examined. Surface deformation was simulated by indenting the alloy in the martensite phase at room temperature using both spherical and pyramidal indenters. We show that deformation in spherical microindents can be almost completely reversed by moderate heating. Partial recovery was observed for pyramidal impressions formed by a Vickers indenter and the recovery ratio was independent of the indentation depth. The observations were rationalized using the concept of representative strain and maximum stress under the spherical and pyramidal indenters. [ABSTRACT FROM AUTHOR]

Surface conditions of flexible electronic devices can affect their accuracy, so it is necessary to keep surfaces clean and stable to ensure their correct-long-term operation. The Nepenthes-inspired slippery surface has excellent self-cleaning, stability, and self-healing properties. A slippery surface with stretching durability is significant for application to a flexible sensors surface. As an advanced micro-nanomanufacturing method, femtosecond laser has become an effective method for preparing porous structures to process a slippery surface. In this study, a femtosecond laser was used to prepare an interconnected porous structure on pre-stretched polydimethylsiloxane in one step. The slippery surface was prepared after being infused with lubricant, which maintained the slippery performance under tensile conditions and after hundreds of stretch cycles. Moreover, it exhibits remarkable self-cleaning and chemical stability. This stretchable slippery surface prepared by femtosecond laser direct writing presents good prospects for flexible electronic devices that require a stable surface in various extreme environmental applications. [ABSTRACT FROM AUTHOR]

The effect of ion mixing on the depth resolution of sputter depth profiling has been studied using x-ray photoelectron spectroscopy and Ar+ sputtering of Pt/Zr, Pt/Mo, Pt/Ti, and Pt/Ni interfaces. It is shown that the heat of mixing of binary alloys plays an important role in depth resolution. The measured interface width of bilayers consisting of metals with a large and negative heat of mixing (Pt/Zr and Pt/Ti) is significantly broader than that of metals with a nearly zero heat of mixing (Pt/Mo and Pt/Ni). This observation suggests that the mechanism of ion mixing during sputter depth profiling with ion energies of a few keV is the same as ion mixing with ion energies of several hundred keV; diffusion in thermal spikes is the dominant contribution to ion mixing in the systems investigated. [ABSTRACT FROM AUTHOR]

A stick-slip/inchworm hybrid rotary piezomotor based on a symmetric triangular driving mechanism, which can simultaneously achieve the benefits of both stick-slip and inchworm motors, was reported in this letter. It is based on the principle of stick-slip motors, and, inspired by the clamping-releasing actions from inchworm motors, it employs a symmetric triangular driving mechanism to generate a clamping action during the stick phase and a releasing action during the slip phase. Compared with stick-slip motors, it involves a clamping action during the stick phase and a releasing action during the slip phase, thus resulting in a larger driving force. Compared with inchworm motors, which require active control and coordination of clamping/releasing modules with feeding modules, it involves the control and operation of only one feeding piezoactuator without any actively controlled clamping/releasing module. Therefore, the control is easier, and a much larger operation frequency and driving speed can be achieved. Under the sawtooth waveform voltage of 90 V at 2600 Hz with a self-holding torque of 4 N m, the prototype achieved a no-load speed higher than 0.6 rad/s, a load torque capacity larger than 1.8 N m, and a weight carrying capacity more than 100 kg for both clockwise and anticlockwise directions. Compared with load torque capacity and weight carrying capacity in the reported stick-slip and inchworm rotary piezomotors, the current levels in terms of the same driving speed have been improved over 60 times and 12 times, respectively, in the proposed hybrid motor. [ABSTRACT FROM AUTHOR]

The anomalous Nernst effect (ANE) is one of the most intriguing thermoelectric phenomena, which has attracted growing interest both for its underlying physics and potential applications. Typically, a large ANE response is observed in magnets with pronounced magnetizations or nontrivial Berry curvature. Here, we report a significant ANE signal in compensated ferrimagnetic CoxGd1-x amorphous films, which exhibit vanishingly small magnetization. In particular, we found that the polarity of ANE signal is dominated by the magnetization orientation of the transition metal Co sublattices, rather than the net magnetization of CoxGd1-x films. This observation is not expected from the conventional understandings of ANE but is analogous to the anomalous Hall effect in compensated ferrimagnets. The joint contribution from the Berry curvature and the scattering mechanisms near the Co-dominant Fermi surface could interpret the Co-dominant property of ANE. Our work may trigger a more comprehensive understanding of ANE and may be useful for building energy-harvesting devices by employing ANE in compensated ferrimagnets. [ABSTRACT FROM AUTHOR]

The electrical conductivity, charge transport behavior, and ferroelectricity of epitaxial BaNbxTi1-xO3 films (BNTO, 0.0≤x≤0.5) prepared by pulsed laser deposition are investigated. It is found that Nb-doping can tune the conventional insulating BaTiO3 films from an insulating to highly conductive semiconducting or metallic state, resulting in a variation of the electrical conductivity of the BNTO films over 105. For x ≤ 0.25, the charge transport is dominated by the small polaron hopping mechanism, while the charge transport for x=0.5 transits from the bipolaron to the small-polaron, and then the thermal phonon scattering mechanisms with increasing temperature. Interestingly, the piezo-force microscopy imaging reveals the presence of ferroelectricity in the properly Nb-doped conductive BNTO films (x≤0.25) deposited in the presence of a small amount of oxygen (3x10-3Pa). Our work provides additional technical roadmaps to manipulate the conductivity and charge transport behaviors in ferroelectric films, which will boost potential applications in future information storage, sensors, and photovoltaic devices. [ABSTRACT FROM AUTHOR]

We have investigated the surface of lithium metal using x-ray photoemission spectroscopy and optical spectroscopic ellipsometry. Even if we prepare the surface of lithium metal rigorously by chemical cleaning and mechanical polishing inside a glovebox, both spectroscopic investigations show the existence of a few tens of nanometer-thick surface layers, consisting of lithium oxides and lithium carbonates. When lithium metal is exposed to room air (∼50% moisture), in situ real-time monitoring of optical spectra indicates that the surface layer grows at a rate of approximately 24 nm/min, presumably driven by an interface-controlled process. Our results hint that surface-layer-free lithium metals are formidable to achieve by a simple cleaning/polishing method, suggesting that the initial interface between lithium metal electrodes and solid-state electrolytes in fabricated lithium metal batteries can differ from an ideal lithium/electrolyte contact. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic halometallates, with different organic and inorganic components, can provide a wide array of tunable physical properties. While many optoelectronic phenomena are being explored, research on the mechanical properties of this class of materials, especially fracture toughness, is lacking, resulting in conclusions on material flexibility being drawn from their elastic modulus and hardness alone with an implicit assumption that these properties correlate with material flexibility. In this Letter, we report nanoindentation results on the elastic modulus, hardness, and fracture toughness of single crystal samples of hybrid organic–inorganic histammonium chlorozincate, HistZnCl4 along the [001] axis. We find that the elastic modulus is 12.078 ± 1.034 GPa, and the hardness is 0.611 ± 0.089 GPa. Moreover, the fracture toughness of this sample is measured to be 0.098 MPa m 1 2 . Although these materials have a hardness to modulus ratio similar to that of metals, they fracture like brittle materials, demonstrating the importance of conducting studies on a material fracture toughness before determining their applicability in flexible device applications. [ABSTRACT FROM AUTHOR]

The work done during indentation is examined using dimensional analysis and finite element calculations for conical indentation in elastic-plastic solids with work hardening. An approximate relationship between the ratio of hardness to elastic modulus and the ratio of irreversible work to total work in indentation is found. Consequently, the ratio of hardness to elastic modulus may be obtained directly from measuring the work of indentation. Together with a well-known relationship between elastic modulus, initial unloading slope, and contact area, a new method is then suggested for estimating the hardness and modulus of solids using instrumented indentation with conical or pyramidal indenters. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the Young's modulus and deformation behavior of electroplated mossy lithium at room temperature investigated by flat punch indentation inside an argon-filled glovebox. The Young's modulus of the mossy lithium with a porosity of about 62.3% is measured to be about 2 GPa, which is smaller than that (∼7.8 GPa) of bulk lithium. Both the mossy and bulk lithium show clearly an indentation creep behavior. Despite its highly porous microstructure, the impression creep velocity of the mossy lithium is less than one-thirtieth of that of bulk lithium under the same stress. We proposed possible mechanisms for the significantly higher deformation and creep resistance of the mossy lithium over bulk lithium. These findings are key to developing mechanical suppression approaches to improve the cycling stability of lithium metal electrodes. [ABSTRACT FROM AUTHOR]

Nanometer-scale gaps in Pd strips are obtained by hydrogen absorption under high pressure treatment. The resulting lattice constant increase due to the Pd phase transformation after hydrogen uptake results in a large compressive stress on the thin Pd films. Under proper geometric arrangement of the Pd electrode within a surface conduction electron (SCE) emitter structure, a single nanogap per SCE device is obtained. A turn-on voltage of 41 V is observed for emitters with a 25 nm gap. [ABSTRACT FROM AUTHOR]

The fabrication process and performance characteristics of a vertical-structured GaN-based light-emitting diode (VM-LED) employing nickel electroplating and patterned laser liftoff techniques are presented. As compared to regular LED, the forward voltage drop of the VM-LED at 20–80 mA is about 10%–21% lower, while the light output power (Lop) is more than twice in magnitude. Especially, the Lop exhibits no saturation or degradation at an injection current up to 520 mA which is about 4.3 times higher than that of the regular one. Substantial improvements in the VM-LEDs performances are mainly attributed to the use of metallic substrate which results in less current crowding, larger effective area, and higher thermal conductivity. [ABSTRACT FROM AUTHOR]