The heavy fermion state with Kondo-hybridization (KH), usually manifested in f-electron systems with lanthanide or actinide elements, was recently discovered in several 3d transition metal compounds without f-electrons. However, KH has not yet been observed in 4d/5d transition metal compounds, since more extended 4d/5d orbitals do not usually form flat bands that supply localized electrons appropriate for Kondo pairing. Here, we report a doping- and temperature-dependent angle-resolved photoemission study on 4d Ca2-xSrxRuO4, which shows the signature of KH. We observed a spectral weight transfer in the γ-band, reminiscent of an orbital-selective Mott phase (OSMP). The Mott localized γ-band induces the KH with an itinerant β-band, resulting in spectral weight suppression around the Fermi level. Our work is the first to demonstrate the evolution of the OSMP with possible KH among 4d electrons, and thereby expands the material boundary of Kondo physics to 4d multi-orbital systems.
Ion migration can cause severe damage to high power semiconductor devices. One of the main sources of mobile ions is the encapsulation material such as molding compounds. Within this work a method will be described to evaluate the risk of field induced ion migration of different molding compounds depending on the temperature and field strength. This method allows the qualitative and quantitative determination of ion mobility in molding compounds, without the interference of electron conductivity.
Already small amounts of ion contamination within sensitive areas of high voltage transistors can cause severe damage to semiconductor devices. Therefore, it is of utmost importance to hinder mobile ions from reaching critical regions (e.g., the gate oxide layer). To protect semiconductor devices from environmental influences and contamination, polymers are used for chip encapsulation. Reduction of ion migration within these polymers can increase the reliability of the semiconductor device. Crown ethers are well known to form stable complexes with alkali cations. Within this work the influence of 15-crown-5 ether on the sodium migration in poly-methyl methacrylate and polyimide will be evaluated by means of ion conductivity measurements.
The heavy fermion state with Kondo-hybridisation (KH), usually manifested in f-electron systems with lanthanide or actinide elements, was recently discovered in several 3d transition metal compounds without f-electrons. However, KH has not yet been observed in 4d/5d transition metal compounds, since more extended 4d/5d orbitals do not usually form flat bands that supply localised electrons appropriate for Kondo pairing. Here, we report a substitution- and temperature-dependent angle-resolved photoemission study on 4d Ca2−xSrxRuO4, which shows the signature of KH. We observed a spectral weight transfer in the γ-band, reminiscent of an orbital-selective Mott phase (OSMP). The Mott localised γ-band induces the KH with an itinerant β-band, resulting in spectral weight suppression around the Fermi level. Our work demonstrates the evolution of the OSMP with possible KH among 4d electrons, and thereby expands the material boundary of Kondo physics to 4d multi-orbital systems.
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