Nejdůležitější publikace 1. období (MATE)

Nejdůležitější odborné publikace vydané během prvního období (do 31. března 2019). Seznam všech publikací výzkumného programu MATE vydaných v rámci projektu CAAS najdete v předchozím příspěvku.

Thermoelectric properties of the tetrahedrite–tennantite solid solutions Cu12Sb4−xAsxS13 and Cu10Co2Sb4−yAsyS13 (0 ≤ xy ≤ 4)
Petr Levinsky, Christophe Candolfi, Anne Dauscher, Janusz Tobola, Jiří Hejtmánek, Bertrand Lenoir
Physical Chemistry Chemical Physics, Issue 8, 2019
Tetrahedrites, a class of copper- and sulfur-rich minerals, exhibit inherently very low lattice thermal conductivity and adjustable electronic properties that make them interesting candidates for thermoelectric applications. Here, we investigate the influence of isovalent As substitution on the Sb site on the structural and transport properties (5–700 K) of the two solid solutions Cu12Sb4−xAsxS13 and Cu10Co2Sb4−yAsyS13 (0 ≤ xy ≤ 4). Electronic band structure calculations predict that As has only a weak influence on the valence bands and hence, on the p-type metallic character of Cu12Sb4S13. In agreement with these predictions, all the samples of the series Cu12Sb4−xAsxS13 exhibit p-type metallic behavior with relatively low electrical resistivity and moderate thermopower values that only slightly evolve with the As content. In contrast, the substitution of Co for Cu in As-rich samples seems less favorable as suggested by a decrease in the Co concentration with increasing the As content. This trend leads to a concomitant increase in the electrical resistivity and thermopower leaving the ZTvalues practically unchanged with respect to purely Cu-based samples. As a result, peak ZT values ranging between 0.60 and 0.75 are achieved at 700 K for both series. The lack of significant variations in the ZT values confirms the robustness of the thermoelectric performances of tetrahedrites with respect to variations in the Sb-to-As ratio.

Atomic-scale design of friction and energy dissipation
Antonio Cammarata, Paolo Nicolini, Kosta Simonovic, Egor Ukraintsev, Tomas Polcar
Phys. Rev. B 99, 094309 – Published 25 March 2019
Study of friction and energy dissipation always relied on direct observations. Actual theories provide limited prediction on the frictional and dissipative properties if only the material chemistry and geometry are known. We here develop a framework to study intrinsic friction and energy dissipation based on the only knowledge of the normal modes of the system at equilibrium. We derive an approximated expression for the first anharmonic term in the potential energy expansion which does not require the computation of the third-order force constants. Moreover, we show how to characterize the frequency content of observed physical quantities and individuate the dissipative processes active during experimental measurements. As a case study, we consider the relative sliding motion of atomic layers in molybdenum disulfide dry lubricant, and we discuss how to extract information on the energetics of sliding from atomic force microscopy signals. The presented framework switches the investigation paradigm on friction and energy dissipation from dynamic to static studies, paving avenues to explore for the design of alternative anisotropic tribological and thermal materials.

A high sensitivity UV photodetector with inkjet printed ZnO/nanodiamond active layers
Josef Nahlik, Alexandr Laposa, Jan Voves, Jiri Kroutil, Jan Drahokoupil, Marina Davydova
IEEE Sensors Journal, Volume: 19, Issue: 14, July 15, 2019
The single- and double-layered photodetectors based on ZnO and/or detonation nanodiamond (DND) have been developed via a sequential inkjet printing on the interdigital electrode platform using a diamond and zinc oxide precursor ink. The morphological structure of the deposited materials was visualized and analyzed by scanning electron microscopy and atomic force microscopy. The crystalline configuration and structural quality of ZnO and nanodiamond were investigated by X-ray diffraction and Raman spectroscopy. The response, response time, and recovery time were measured for different UV wavelengths (365, 385, and 405 nm), light intensities, temperatures, and bias voltages. The ZnO/DND structure shows more than ten times higher response and faster reactivity in comparison with a single-layered photodetector. Photoresponsivity of the double-layered photodetector (ZnO/DND) is 0.35 A $\cdot \,\,\text{W}^{ {-1}}$ , whereas bare ZnO is about 0.039 A $\cdot \,\,\text{W}^{{-1}}$ . The interaction between UV light and ZnO/DND grains was investigated by two dimensional Silvaco TCAD simulation.