Autor CND

Inštalácia FIB-SEM mikroskopu

Začiatkom Júna sa v priestoroch Centra pre Nanodiagnostiku Materiálov, ktoré patrí pod MTF Trnava, začala inštalácia nového FIB-SEM mikroskopu. Zariadenie bolo privezené z výrobného závodu firmy Thermo Fisher Scientific (bývalá firma FEI) v Brne do Bratislavy, kde bolo inštalované v novo zrekonštruovaných priestoroch Centra. Po náročnom transporte zariadenia do suterénu, bol mikroskop úspešne zostavený a spustený. Po následnej sérii nastavení, kalibrácií a testov bol mikroskop odskúšaný a uvedený do prevádzky. Keďže mikroskop spĺňa požadované parametre, môžeme konštatovať, že mikroskop je pripravený splniť všetky náročné požiadavky, ktoré sú naň kladené.

Mikroskop dorazil do Bratislavy
Inštalácia
Covalent Diamond–Graphite Bonding: Mechanism of Catalytic Transformation

Covalent Diamond–Graphite Bonding: Mechanism of Catalytic Transformation

Semir Tulić, Thomas Waitz, Mária Čaplovičová, Gerlinde Habler, Marián Varga, Mário Kotlár, Viliam Vretenár, Oleksandr Romanyuk, Alexander Kromka, Bohuslav Rezek, Viera Skákalová

ACS Nano, 2019, 1344621-4630

https://doi.org/10.1021/acsnano.9b00692

Abstract

Aberration-corrected transmission electron microscopy of the atomic structure of diamond–graphite interface after Ni-induced catalytic transformation reveals graphitic planes bound covalently to the diamond in the upright orientation. The covalent attachment, together with a significant volume expansion of graphite transformed from diamond, gives rise to uniaxial stress that is released through plastic deformation. We propose a comprehensive model explaining the Ni-mediated transformation of diamond to graphite and covalent bonding at the interface as well as the mechanism of relaxation of uniaxial stress. We also explain the mechanism of electrical transport through the graphitized surface of diamond. The result may thus provide a foundation for the catalytically driven formation of graphene–diamond nanodevices.

Effect of temperature and carrier gas on the properties of thick InxAl1-xN layer

Effect of temperature and carrier gas on the properties of thick InxAl1-xN layer

Prerna Chauhan, Stanislav Hasenöhrl, Edmund Dobročka, Ľubomír Vančo, Roman Stoklas, Jaroslav Kováč, Peter Šiffalovič, Ján Kuzmík

doi.org/10.1016/j.apsusc.2018.10.231

Abstract

Thick (>150nm) InxAl1-xN layers were grown on GaN/sapphire (0001) by organometallic vapor phase epitaxy. Growth temperature of InxAl1-xN layers was reduced from 790 to 730°C, to examine the effects of growth temperature in InxAl1-xN layers grown under H2 carrier gas. Indium incorporation, surface morphology, electrical, and optical properties of InxAl1-xN layers were examined as a function of growth temperature. Increase in In-molar fraction, as determined by high resolution X-ray diffraction, was observed with decreasing growth temperature of InxAl1-xN layers at the expense of surface roughness. Unstrained InxAl1-xN layer was achieved at 730°C under H2 carrier gas with x=0.18. However, InxAl1-xN layer grown under N2 carrier gas at 730°C to study the effects of carrier gas, was observed with two times higher In-molar fraction (x=0.37) and one order lower carrier concentration. This work shows the essential requirement of a multi-characterization approach to establish a connection between structural, electrical, and optical properties to improve our understanding towards InxAl1-xN. Edge threading dislocations density is found to be the most important parameter in deciding the characteristics of an InxAl1-xN layer.

Adhesive-deformation relationships and mechanical properties of nc-AlCrN/a-SiNx hard coatings deposited at different bias voltages

Adhesive-deformation relationships and mechanical properties of nc-AlCrN/a-SiNx hard coatings deposited at different bias voltages

M. Haršáni, N. Ghafoor, K. Calamba, P. Zacková, M. Sahul, T. Vopát, L. Satrapinskyy, M. Čaplovičová, Ľ. Čaplovič,

Thin Solid Films, Volume 650, 2018, Pages 11-19

doi.org/10.1016/j.tsf.2018.02.006

Abstract

A series of Al-Cr-Si-N hard coatings were deposited on WC-Co substrates with a negative substrate bias voltage ranging from −50 to −200 V using cathodic arc evaporation system. A Rockwell-C adhesion test demonstrated that excellent adhesion was observed at lower bias voltages of −50 V and −80 V, while further increases in bias voltage up to −200 V led to severe delaminationand worsening of the overall adhesion strength. X-ray diffraction and transmission electron microscopy analysis revealed a single phase cubic B1-structure identified as an AlCrN solid solution with a nanocomposite microstructure where cubic AlCrN nanocrystals were embedded in a thin continuous amorphous SiNx matrix. Coatings exhibited a 002-texture evolution that was more pronounced at higher bias voltages (≥−120 V). Stress-induced cracks were observed inside the coatings at high bias voltages (≥−150 V), which resulted in stress relaxation and a decline in the overall residual stresses.
Thermally induced age hardening in tough Ta-Al-N coatings via spinodal decomposition

Thermally induced age hardening in tough Ta-Al-N coatings via spinodal decomposition

Mikula, M., Sangiovanni, D.G., Plašienka, D., Roch, T., Čaplovičová, M., Truchlý, M., Satrapinskyy, L., Bystrický, R., Tonhauzerová, D., Vlčková, D., Kúš, P.

Journal of Applied Physics 121, 2017, 155304

doi.org/10.1063/1.4981534

Abstract

We combine experiments and ab initio density functional theory calculations to investigate the evolution in structural and mechanical properties of TaAlN coatings as a function of the annealing temperature T. Formation of coherent cubic TaN- and AlN-rich nanometer-size domains, occurring during the initial stage of thermally induced phase separation within cubic NaCl-type (B1) TaAlN solid solutions, yields a monotonic increase in hardness from 29 GPa (as deposited coatings) up to a maximum of 35 GPa (+17%) reached after annealing at 1000 °C. Further thermal treatment at T > 1000 °C leads to the transformation of metastable cubic domains into stable hexagonal TaNx and wurtzite AlN phases, thus resulting in hardness reductions. A comparison of our results with those reported in the literature reveals that TaAlN coatings are at least as hard while considerably less stiff (lower elastic moduli) than TiAlN coatings, thus indicating a substantial increase in toughness achieved upon replacing Ti with Ta in the host lattice. Present findings suggest that cubic TaAlN solid solutions are promising candidates for applications in protective coatings possessing both high-temperature hardness and toughness. © 2017 Author(s).

Influence of GaN/AlGaN/GaN (0001) and Si (100) substrates on structural properties of extremely thin MoS2 films grown by pulsed laser deposition

Influence of GaN/AlGaN/GaN (0001) and Si (100) substrates on structural properties of extremely thin MoS2 films grown by pulsed laser deposition

Š. Chromik, M. Sojková, V. Vretenár, A. Rosová, E. Dobročka, M. Hulman

doi.org/10.1016/j.apsusc.2016.06.038

Abstract

Very thin MoS2 films were prepared on hexagonal GaN/AlGaN/GaN (0001) and Si (100) substrates from a stoichiometric target by a pulsed laser deposition. Combined results from Raman and X-ray reflectivity measurements have shown that the thinnest samples are 2–2.5nm thick. The thickness increases with the number of laser pulses applied albeit no simple direct proportion between the two quantities has been observed. Concerning the stoichiometry, the distribution of Mo and S elements within as-deposited films is rather complex. The stoichiometric MoS2 is making-up only a part of the film. In spite of this, selected area electron diffraction studies have clearly confirmed that the films deposited on Si (100) are nanocrystalline and oriented perpendicularly to the substrate surface while an epitaxial growth of MoS2 films was observed on GaN/AlGaN/GaN (0001) substrates.