Micromechanical testing of Mo‐B‐C layers prepared by magnetron sputtering

Based on attractive mechanical properties of transition metal diborides the group of X2BC ternary compounds (X = Ti, V, Zr, Nb, Mo, Hf, Ta and W) became subject of theoretical calculations [1-3] and lately proved their applicability experimentally [4]. X2BC with X = Mo, Ta and W are the most promising candidates for protection of cutting and forming tools due to their unusually stiffness and moderately ductility. These properties can be understood by considering the electronic structure and particularly the extreme anisotropy (orthorhombic crystal lattice with a=0.309nm, b=1.735nm, c=0.305nm). Please click Additional Files below to see the full abstract

Study of the transition from self-organised to homogeneous plasma distribution in chromium HiPIMS discharge

Publisher's version (útgefin grein)The self-organised plasma patterns, known as spokes or ionisation zones in magnetron sputtering discharges, were observed in a wide range of power densities, from low power direct current magnetron sputtering (dcMS) discharge to high power impulse magnetron sputtering (HiPIMS) discharge. For some target materials and non-reactive gases, it was observed that at very high power densities (>3 kW cm-2) the plasma exhibits a transition from a regime where spokes are observed to a homogeneous plasma regime. In this contribution, we present a comparison of plasma properties: plasma emission (optical emission spectroscopy) and flux of argon and chromium ions (mass spectrometry), measured both in the spoke regime and in the homogeneous plasma regime, aimed to expand the understanding of the plasma transition between the two modes. A simple biased flat probe was used to distinguish between the spoke regime and the homogeneous plasma regime. It was found that the flux of multiply charged ions (Ar2+, Cr2+, Cr3+, Cr4+) increases abruptly at the transition between the spoke regime and the homogeneous plasma regime. Similarly, the emission from Cr+ ions exhibits a strong increase of about 50% when the plasma torus becomes homogeneous. These observations are interpreted as an increase in electron temperature and a change in the electron heating mode, from a combination of secondary electron heating and Ohmic heating towards pure Ohmic heating. The transition to the homogeneous plasma regime and pure Ohmic heating is only observed in non-reactive HiPIMS discharges for target atoms with the second ionisation potential higher than the first ionisation potential of Ar (15.76 eV), and a self-sputter yield larger than 1.This research has been supported by project LM2018097 funded by the Ministry of Education, Youth and Sports of the Czech Republic and project GA19-00579S funded by the Czech Science Foundation. This work has been supported by the German Science Foundation (DFG) within the frame of the collaborative research centre SFB-TR 87Peer Reviewe

Harmonic analysis of discharge voltages as a tool to control the RF sputtering deposition process

The reactive magnetron sputtering deposition process controlled by the flow of the reactive gas exhibits processing stability problems. Since the optimal experimental conditions lie very close to the abrupt transition from the metallic to the compound mode, the range at which the films with the right stoichiometry are deposited at high deposition rates is strongly limited and permanent process monitoring is necessary. A sensitive method for the process monitoring is proposed which is based on the measurement of amplitudes of fundamental or higher harmonic frequencies of discharge voltages during the radio-frequency sputtering deposition process. The voltage waveform recorded by the uncompensated probe placed in the vicinity of the plasma contains much higher relative proportion of higher harmonics than the waveform measured on the cathode. Some of the harmonics are extremely sensitive markers of the transition between the two regimes of interest. For example, the amplitude of some harmonics measured by the probe change severalfold by the transition compared to the conventionally used bias on the cathode, which changes typically only by a few percents. The proposed method can even reach the sensitivity of the optical emission spectroscopy mainly for the reactive sputtering of those elements whose sputtering yield does not differ substantially in the metallic and in the compound state

Aggressive systemische Mastozytose mit erhöhter diffuser 18F-FDG-Aufnahme im Knochenmark [Aggressive systemic mastocytosis with diffuse bone marrow 18F-FDG uptake]

Mastocytosis is a clonal hematopoietic disorder characterized by proliferation of abnormal mast cells in various organs including the skin, digestive system, lymph nodes, and bone marrow. We report on a 75-year-old woman presenting with abdominal pain, vomiting, diarrhoea, myalgia, and weight loss. Abdominal CT showed hepatosplenomegaly with heterogeneous splenic parenchyma, lymphadenopathy, and osteopenia with areas of osteosclerosis but no primary tumour. An <sup>18</sup> F-FDG PET/CT revealed an overall low metabolic activity of the lesions with a diffuse bone marrow involvement raising suspicion of a haematological neoplasm. Subsequently, bone marrow and peripheral blood examinations confirmed the diagnosis of aggressive systemic mastocytosis