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237 results on '"Scholz, Mirko"'

5. Excited-State Dynamics of Bis(tetraethylammonium) Di-µ-bromo-dibromodicuprate(I) Thin Films.

Author

Gust, Domenic, Scholz, Mirko, Oum, Kawon, and Lenzer, Thomas

Subjects
*THIN films, *TETRAETHYLAMMONIUM, *ACOUSTIC phonons, *PHONON scattering, *EXCITED states
Abstract

Organic–inorganic halocuprates based on monovalent copper are promising luminescent compounds for optoelectronic applications; however, their relaxation processes in the excited electronic state are severely underexplored. In this contribution, we prepare thin films of bis(tetraethylammonium) di-µ-bromo-dibromodicuprate(I) [N(C2H5)4]2[Cu2Br4], abbreviated (TEA)2Cu2Br4, which features a "molecular salt" structure containing discrete [Cu2Br4]2− anions. This compound, which has an absorption peak at 283 nm, displays a blue, strongly Stokes-shifted emission with a peak at 467 nm. Transient photoluminescence (PL) experiments using broadband emission detection and time-correlated single-photon counting (TCSPC) both find an excited-state lifetime of 57 μs at 296 K. UV–Vis transient absorption experiments at 296 K covering time scales from femto- to microseconds provide evidence for the formation of the T1 state through intersystem crossing from S1 with a time constant of 184 ps. The triplet state subsequently decays to S0 predominantly by phosphorescence. In addition, the time constants for carrier–optical phonon scattering (1.8 ps) and acoustic phonon relaxation (8.3 ns and 465 ns) of (TEA)2Cu2Br4 are provided. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Characterization and optimization of sub-32-nm FinFET devices for ESD applications

Author

Thijs, Steven, Tremouilles, David, Russ, Christian, Griffoni, Alessio, Collaert, Nadine, Rooyackers, Rita, Linten, Dimitri, Scholz, Mirko, Duvvury, Charvaka, Gossner, Harald, Jurczak, Malgorzata, and Groeseneken, Guido

Subjects
Metal oxide semiconductor field effect transistors -- Electric properties, Metal oxide semiconductor field effect transistors -- Mechanical properties, Business, Electronics, Electronics and electrical industries
Abstract

The behavior of FinFET devices is analyzed under electrostatic discharge (ESD) conditions for various layout and process conditions. The results have shown that the possible extreme sensitivity of FinFET devices might not be a showstopper for the advanced nanotechnologies if ESD is considered during the technology development.

Published
2008

39. Exploring Differences in Excited-State Properties of Styryl-BODIPY Chromophores upon Change from α- to β-Substitution.

Author

Scholz, Mirko, Hoffmann, Caroline, Klein, Johannes R., Wirtz, Marcel, Jung, Gregor, and Oum, Kawon

Abstract

We present a femtosecond pump-probe UV-Vis broadband transient absorption spectroscopy study of two styryl-substituted BODIPY chromophores with different position of the substituent. The α-substituted isomer shows typical BODIPY-type spectral features, such as sharp absorption and emission bands, a small Stokes shift and an excited-state lifetime in the 4 ns range, which only weakly depends on the solvent. In contrast, β-styryl-BODIPY features much broader steady-state absorption and emission spectra and a larger Stokes shift, particularly in polar solvents. Transient absorption spectroscopy including a complete global kinetic analysis reports a substantial decrease in S1 lifetime to 300 ps for polar solvents upon change from α- to β-substitution. In the case of the α-isomer, TD-DFT calculations identify a typical "cyanine-type" electron rearrangement upon S0 → S1 excitation accompanied by a slight reduction in dipole moment. In contrast, the same transition in the β-isomer shows strong intramolecular charge transfer (ICT) character involving a substantial increase in dipole moment. Assuming a simple energy-gap-law argument, the accelerated nonradiative decay of the β-isomer in polar solvents may be linked to the decrease of the S1(ICT)-S0 energy difference. BODIPY dyes with a conjugated substituent in β-position therefore suffer a substantial loss in fluorescence brightness in polar environments compared with their α-substituted counterparts. This might limit their applicability in fluorescence imaging. [ABSTRACT FROM AUTHOR]

Published
2020
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40. Ultrafast Excited-State Dynamics of all-trans-Capsanthin in Organic Solvents

Author

Scholz, Mirko, Flender, Oliver, Lenzer, Thomas, and Oum, Kawon

Abstract

The C40carotenoid capsanthin is of photophysical interest because it belongs to the family of terminally carbonyl-substituted apocarotenes. These have the potential to exhibit intramolecular charge transfer (ICT) character in the excited state. We studied its ultrafast dynamics in different solvents using broadband transient absorption spectroscopy in the 260–1600 nm range. Photoexcitation initially populated the S2(11Bu+) state which decayed to the S1(21Ag–) state in 120–150 fs. The lifetime of the S1state decreased from 10.3 ps (isooctane) to 9.1 ps (methanol). Together with the absence of stimulated emission this suggested a weak ICT character of S1. A steric influence of the five-membered ring in capsanthin was identified based on a comparison with the sister apocarotenone citranaxanthin which features methyl substitution at the keto group. While both apocarotenones exhibit the same S1lifetime in isooctane, the decrease in lifetime in polar solvents is weaker for capsanthin because presumably the five-membered ring sterically perturbs stabilization of ICT character by the solvent. For the S1state of capsanthin we further observed intramolecular vibrational redistribution and collisional energy transfer to the solvent with time constants of 340–420 fs and 8.5–9.1 ps, respectively. No evidence for excited-state photoisomerization of capsanthin was found.

Published
2024
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50. ESD ballasting of Ge FinFET ggNMOS devices

Author

Boschke, Roman, primary, Chen, Shih-Hung, additional, Scholz, Mirko, additional, Hellings, Geert, additional, Linten, Dimitri, additional, Witters, Liesbeth, additional, Collaert, Nadine, additional, and Groeseneken, Guido, additional

Published
2017
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