[en] Short note

No abstract available

[en] The frequencies of the long-wavelength lattice vibrations of SnS crystal with a layered crystal structure have been calculated in the linear chain framework. It has been shown that these frequencies fall as the size of the crystal across layers decreases. A significant softening of the low-frequency Raman-active modes has been established as the thickness of a crystal is reduced to two layers. (author)

[en] To extend materials design and discovery into the space of metastable polymorphs, rapid and reliable assessment of transformation kinetics to lower energy structures is essential. Herein we focus on diffusionless polymorphic transformations and investigate routes to assess their kinetics using solely crystallographic arguments. As part of this investigation we developed a general algorithm to map crystal structures onto each other, and ascertain the low-energy (fast-kinetics) transformation pathways between them. Pathways with minimal dissociation of chemical bonds, along which the number of bonds (in ionic systems the first-shell coordination) does not decrease below that in the end structures, are shown to always be the fast-kinetics pathways. These findings enable the rapid assessment of the kinetics of polymorphic transformation and the identification of long-lived metastable structures. In conclusion, the utility is demonstrated on a number of transformations including those between high-pressure SnO₂ phases, which lack a detailed atomic-level understanding.

[en] This work reports on direct evidence of localized states in undoped SnO₂ nanobelts. Effects of disorder and electron localization were observed in Schottky barrier dependence on the temperature and in thermally stimulated currents. A transition from thermal activation to hopping transport mechanisms was also observed. The energy levels found by thermally stimulated current experiments were in close agreement with transport data confirming the role of localization in determining the properties of devices. (paper)

[en] The directional design of functional materials with multi-objective constraints is a big challenge, in which performance and stability are determined by a complicated interconnection of different physical factors. We apply multi-objective optimization, based on the Pareto Efficiency and Particle-Swarm Optimization methods, to design new functional materials directionally. As a demonstration, we achieve the thermoelectric design of 2D SnSe materials via the above methods. We identify several novel metastable 2D SnSe structures with simultaneously lower free energy and better thermoelectric performance in their experimentally reported monolayer structures. We hope that the results of our work on the multi-objective Pareto Optimization method will represent a step forward in the integrative design of future multi-objective and multi-functional materials. (paper)

[en] Nanostructured materials are promising candidates for chemical sensors due to their fascinating physicochemical properties. Among various candidates, tin oxide (SnO₂) has been widely explored in gas sensing elements due to its excellent chemical stability, low cost, ease of fabrication and remarkable reproducibility. We are presenting an overview on recent investigations on 1-dimensional (1D) SnO₂ nanostructures for chemical sensing. In particular, we focus on the performance of devices based on surface engineered SnO₂ nanostructures, and on aspects of morphology, size, and functionality. The synthesis and sensing mechanism of highly selective, sensitive and stable 1D nanostructures for use in chemical sensing are discussed first. This is followed by a discussion of the relationship between the surface properties of the SnO₂ layer and the sensor performance from a thermodynamic point of view. Then, the opportunities and recent progress of chemical sensors fabricated from 1D SnO₂ heterogeneous nanostructures are discussed. Finally, we summarize current challenges in terms of improving the performance of chemical (gas) sensors using such nanostructures and suggest potential applications. (author)

[en] Different tin sulfide nanostructures, such as nanobelts, nanorightangles, nanorods, and nanosheets, have been synthesized via an efficient solvothermal process. The thickness and width of SnS nanobelts are less than 30 nm and in the range of 50-300 nm, respectively. A nanorightangle is composed of two nanobelts. The influence of synthetic parameters, such as reaction temperature and sulfur sources, on the morphologies of tin sulfide has been investigated

[en] Two-dimensional (2D) materials attached with flexible substrates enable possibilities to apply their superior properties to the rapidly increasing demand for foldable displays and wearable biosensors in the internet-of-things technology. However, previous two-step strategy to construct the flexible devices, namely first obtaining 2D materials elsewhere and then transferring them onto flexible substrates, can cause huge problems, including irreversibly undermining the device performance and limiting the material size. Here we propose a new one-step strategy (other than the liquid phase processing and low temperature synthesis methods), namely directly depositing appropriate 2D materials onto flexible substrates, which involves no transferring and can maintain the crystal quality and properties to the greatest extent. More importantly, this strategy in principle has no limit in the film size, hence removing a main obstacle for the practical use of flexible films, such as complex logic operations and large-area optoelectronic applications. Using this strategy, a centimeter-scale SnSe₂ film is directly grown on polydimethylsiloxane, which is characterized as a uniform, out-of-plane oriented and semiconducting film that is robust to deformations. Based on the film, a flexible photodetector is fabricated and distinct photoresponse to a broad spectrum of light (405–830 nm) is observed, with remarkable technical parameters. (paper)

[en] TlZnSnO films, fabricated by sputtering with TlZnSnO targets composed of TlZnSnO powder, which was prepared via two-stage calcination, were analyzed. This study reports the first trial of TlZnSnO film preparation, and its optical and electrical properties. Tl atom concentrations of 0.9–1.36 at.% in the TlZnSnO films changed the bandgap between 2.83 and 3.07 eV. The obtained TlZnSnO ionization potential of 5.57–5.9 eV was slightly smaller than that of amorphous InGaZnO (a-IGZO). We also found that the conduction band was located approximately around 3 eV or lower beneath the vacuum level for each examined film; and that a deep density of state (DOS) exists near the valence band. A similar subgap DOS to that of a-IGZO existed even in TlZnSnO. However, the bandgap (2.83–3.07 eV) and donor level (31 meV) of TlZnSnO are smaller than those of a-IGZO. (paper)