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Photolithography is the prevalent microfabrication technology. It needs to meet resolution and yield demands at a cost that makes it economically viable. However, conventional far-field photolithography has reached the diffraction limit, which imposes complex optics and short-wavelength beam source to achieve high resolution at the expense of cost efficiency. Here, we present a cost-effective near-field optical printing approach that uses metal patterns embedded in a flexible elastomer photomask with mechanical robustness. This technique generates sub-diffraction patterns that are smaller than 1/10th of the wavelength of the incoming light. It can be integrated into existing hardware and standard mercury lamp, and used for a variety of surfaces, such as curved, rough and defect surfaces. This method offers a higher resolution than common light-based printing systems, while enabling parallel-writing. We anticipate that it will be widely used in academic and industrial productions., Photolithography is an established microfabrication technique but commonly uses costly shortwavelength light sources to achieve high resolution. Here the authors use metal patterns embedded in a flexible elastomer photomask with mechanical robustness for generation of subdiffraction patterns as a cost effective near-field optical printing approach.

The thermoelectric transport properties of Bi/Sn and Bi/Sb core/shell (C/S) nanowires grown by the method of on-film formation of nanowires were systematically investigated. The electrical conductivity and Seebeck coefficient of nanowires with different diameters were measured as a function of the temperature. The contribution of Sn and Sb shells to the total transport in the C/S nanowires was determined using analytical fitting based on the parallel combination of the conductive system model. The carrier-interface boundary scattering at the C/S interface was quantitatively evaluated as the sheet resistance. In addition, the effect of hole doping on the transport properties was also observed in the Bi/Sn C/S nanowires.

Electronic band engineering is a promising approach to enhance the thermopower of thermoelectric materials. In transition-metal dichalcogenides (TMDCs), this has so far only been achieved using their inherent semiconducting nature. Here, we report the thickness-modulated band engineering of nanosheets based on semimetallic platinum diselenide (PtSe2) resulting in a thermopower enhancement of more than 50 times than that of the bulk. We obtained this by introducing a semimetal to semiconductor (SMSC) transition resulting in the formation of a bandgap. This approach based on semimetallic TMDCs provides potential advantages such as a large variation of transport properties, a decrease of the ambipolar transport effect, and a high carrier density dependence of the transport properties. Our observations suggest that the SMSC transition in TMDCs is a promising and straightforward strategy for the development of two-dimensional nanostructured thermoelectric materials.

With the recent reillumination of the hydrogen economy around the world, the demand for H2 sensors is expected to increase rapidly. Due to safety issues caused by the highly flammable and explosive character of hydrogen gas (H2 ), it is imperative to develop the sensors that can quickly and sensitively detect H2 leaks. For the development of H2 sensors, Pd-based materials have been extensively used due to the high affinity of Pd metal for H2 . Among Pd-based H2 sensors, Pd nanogap-based sensors have been extensively investigated because these sensors can operate in an on-off manner, which enables them to have improved sensing capabilities, including high sensitivity, rapid response, short recovery time, and good reliability. Importantly, significant advances in H2 -sensing performance have been achieved by simply using an elastomeric substrate to form Pd nanogaps. Herein, the progress and advanced approaches achieved over the last decade for Pd nanogap-based H2 sensors supported on elastomeric substrates are reviewed, with a focus on strategies to reduce detection limits and increase reliability, sensitivity, and stability.

We investigated the additional (secondary) cooling effect of casted strips on the magnetic properties of Nd–Fe–B sintered magnets. The Nd–Fe–B sintered magnets were fabricated with the casted strips prepared without and with additional cooling. Additional cooling was achieved by blowing Ar gas at various pressures (0.1, 0.3, and 0.6 MPa) on the free-side surface of the strips during the strip-casting process. The higher magnetic properties of Hc, Br, and (BH)max of the final Nd–Fe–B sintered magnets were obtained for 0.1 MPa rather than for 0.0 MPa. The best microstructure of the columnar grains in the casted strips was produced with the aid of a lower pressure of gas on the free-side surface. It was found that the microstructure of the strips affects the distribution of grains grown in the sintered magnets. This report demonstrates that the improved magnetic performance of Nd–Fe–B sintered magnets was achieved via additional gas cooling.

We present the effect of multilayer deposition on the magnetic properties of MnBi thin films. The multilayered MnBi films were fabricated with alternating deposition of Bi and Mn with N ( N = 2–10) layers (L), followed by in situ thermal annealing. As N increases, the even-layered and odd-layered films show a similar layer-number-dependence of the magnetic properties, such as an increasing behavior for H c and a concave-up behavior for M r and ( BH ) max . Higher magnetic properties were obtained at 9L and 10L. According to the electron microscopy analyses, different morphologies and elemental distributions were observed at different N (e.g., smooth-surfaced MnBi film with Bi islands at 2L and uneven-surfaced MnBi film at 10L). The different distributions of microstructure and chemical components are associated with the layer-dependent magnetic properties of the MnBi films.

Al 2 O 3 nanoparticles-embedded single-crystalline Bi nanowires were successfully synthesized without using any templates via the spontaneous growth of Bi thin films covered with Al 2 O 3 nanoparticles. It is experimentally confirmed that Al 2 O 3 nanoparticles were embedded into the single-crystalline Bi nanowires by using the high-resolution transmission electron microscopy and energy dispersive X-ray spectrometry. The temperature-dependent thermal conductivities of individual Al 2 O 3 nanoparticles-embedded single-crystalline Bi nanowires were measured directly using suspended micro-devices. The thermal conductivities of the Al 2 O 3 nanoparticles-embedded Bi nanowires were found to be extremely low compared with those of pure Bi nanowires of similar diameters. Moreover, the thermal conductivity of the Al 2 O 3 nanoparticles-embedded Bi nanowires was not size-dependent, i.e., it did not vary for nanowires with significantly different diameters. This result suggests that the phonon-boundary scattering is not the dominant phonon scattering mechanism in these systems while the phonon-boundary scattering is dominant in the pure single-crystalline nanowires. From the experimental measurements and theoretical calculation, these drastic reduction and unique tendency in the thermal conductivities of Al 2 O 3 nanoparticles-embedded Bi nanowires were explained by the combined effect of the phonon-boundary scattering and impurity scattering occurring between the embedded Al 2 O 3 nanoparticles and Bi matrix.

We investigated the magnetic properties of large, compacted, sintered MnBi bulk magnets with dimensions of 20.3 × 15.3 × 10.3 mm 3 . To obtain a high content of the low-temperature-phase (LTP) of MnBi in the precursor powders, a new process was implemented and produced about 98 wt% of LTP. To improve the coercive field of MnBi, particle sizes were controlled using different milling techniques. The dependence of magnetic properties of the bulk magnets on the particle size was analyzed. The highest maximum energy product, ( BH ) max , obtained among our samples was 7.3 MGOe. This is the first report of demonstrating high performance in large-sized MnBi bulk magnets.

The enhancement in electrical transport properties of exfoliated individual RuO2 NSs was systemically investigated for their application in flexible electronics and optoelectronics. Decoration of Ag NPs on the surface of the RuO2 NSs provides donor electrons and dramatically increases the electrical conductivity of the monolayer RuO2 NSs by up to 3700%. The n-type doping behavior was confirmed via Hall measurement analysis of the doped RuO2 NSs. The layer number- and temperature-dependence of the conductivity were also investigated. Moreover, carrier concentration and mobility were obtained from Hall measurements, indicating that the undoped RuO2 NSs had ambipolar transport and semi-metallic characteristics. Moreover, the Ag-doped RuO2 NS multilayer films on polycarbonate substrates were demonstrated by the Langmuir–Blodgett assembly methods, showing one-third reduction in the sheet resistance and extraordinarily high bending stability that the change in the resistance was less than 1% over 50 000 cycles.

In two-dimensional van der Waals crystals, the interlayer stacking sequence often leads to a change in crystal symmetry and, thus, new polymorphs, leading to an abundant array of physical properties. In this paper, we report the polymorphic form of 2H–3R–NbSe2 that exhibits a substantial difference in terms of the gate dependence of semimetallic behavior and Seebeck coefficient, compared to the well-known 2H–NbSe2 with metallic transport behavior. The semimetallic features of 2H–3R–NbSe2 indicate the presence of minor carriers, confirmed through theoretical calculations, which is in good agreement with the transport behavior. Our results reveal perspectives for understanding the metastable 2H–3R phase NbSe2, which is not far from equilibrium, and for engineering the materials necessary for efficient energy harvesting.

Wetting of the liquid metal on the solid electrolyte of a liquid metal battery controls the operating temperature and performance of the battery. Liquid sodium electrodes are particularly attractive because of their low cost, natural abundance, and geological distribution. However, they wet poorly on a solid electrolyte near its melting temperature, limiting their widespread suitability for low-temperature batteries to be used for large-scale energy storage systems. Herein, we develop an isolated metal-island strategy that can improve sodium wetting in sodium-beta alumina batteries that allows operation at lower temperatures. Our results suggest that in situ heat treatment of a solid electrolyte followed by bismuth deposition effectively eliminates oxygen and moisture from the surface of the solid electrolyte, preventing the formation of an oxide layer on the liquid sodium, leading to enhanced wetting. We also show that employing isolated bismuth islands significantly improves cell performance, with cells retaining 94% of their charge after the initial cycle, an improvement over cells without bismuth islands. These results suggest that coating isolated metal islands is a promising and straightforward strategy for the development of low-temperature sodium-β alumina batteries.

The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350-450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior. By contrast, the sign of the Seebeck coefficient for Ag nanoparticle-doped RuO2 nanosheets does not change with temperature, indicating that the extra charge carriers from metal nanoparticles promote n-type semiconductor behavior.

The anisotropy in the thermoelectric-transport properties of single-crystalline Bi nanowires was systematically investigated. Bi nanowires were grown along the crystal orientations of the [-102] and [100] directions using the on-film formation of nanowires method. The electrical conductivity and Seebeck coefficient of Bi nanowires with different diameters were measured with respect to temperature in both directions. The temperature dependence in electrical conductivity exhibited a significant diameter dependence, and significant anisotropy was observed in the Seebeck coefficient. Anisotropy was also observed in the thermoelectric power factor. The thermoelectric figure of merit was estimated using our previously reported thermal-conductivity data, which indicate that [100]-oriented Bi nanowires are more suitable for thermoelectric applications than [-102] nanowires. This is the first report of the anisotropy investigating all the thermoelectric-transport properties of single-crystalline Bi nanowires.