Lucian Mathes
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View article: A model for positron annihilation in multi-layer systems by solving the diffusion equation using different positron affinities
A model for positron annihilation in multi-layer systems by solving the diffusion equation using different positron affinities Open
We present a method for solving the positron diffusion equation in multi-layer systems. Our approach incorporates material-specific implantation profiles, diffusion parameters, and positron affinities. It utilizes a Markov chain approach t…
View article: Identification and Reversible Optical Switching of NV<sup>+</sup> Centers in Diamond
Identification and Reversible Optical Switching of NV<sup>+</sup> Centers in Diamond Open
Positive nitrogen‐vacancy centers (NV + ) in diamond are predicted to exist in conjunction with neutral (NV 0 ) and negative (NV − ) centers. However, the existence of NV + has only been indirectly inferred through a shift of the Fermi lev…
View article: Tungsten oxide thin films probed by depth-resolved positron annihilation spectroscopy
Tungsten oxide thin films probed by depth-resolved positron annihilation spectroscopy Open
Tungsten oxide (WOx) films grown on tungsten (W) are characterized by depth-resolved Doppler-broadening spectroscopy (DBS) and positron-annihilation lifetime spectroscopy (PALS) as primary analytical methods. The WOx films are prepared on …
View article: Surface and near-surface positron annihilation spectroscopy at very low positron energy
Surface and near-surface positron annihilation spectroscopy at very low positron energy Open
We present a monoenergetic positron beam specifically tailored to the needs of (near-) surface positron annihilation spectroscopy. The Setup for LOw-energy Positron Experiments (SLOPE) comprises a high-activity 22 Na source, a tungsten mod…
View article: Surface and Near-Surface Positron Annihilation Spectroscopy at Very Low Positron Energy
Surface and Near-Surface Positron Annihilation Spectroscopy at Very Low Positron Energy Open
We present a monoenergetic positron beam specifically tailored to the needs of (near-) surface positron annihilation spectroscopy. The Setup for LOw-energy Positron Experiments (SLOPE) comprises a high-activity 22Na source, a tungsten mode…
View article: Nanocomposite versus solid solution formation in the TiSiN system
Nanocomposite versus solid solution formation in the TiSiN system Open
This work contributes to the ongoing scientific debate on the structure of TiSiN coatings. In order to illuminate the formation of a nanocomposite structure versus the formation of a Ti1-xSixN solid solution, a series of TiSiN coatings was…
View article: Imaging low-energy positron beams in real-time with unprecedented resolution
Imaging low-energy positron beams in real-time with unprecedented resolution Open
View article: Imaging low-energy positron beams in real-time with unprecedented resolution
Imaging low-energy positron beams in real-time with unprecedented resolution Open
Particle beams focused to micrometer-sized spots play a crucial role in forefront research using low-energy positrons. Their expedient and wide application, however, requires highly-resolved, fast beam diagnostics. We have developed two di…
View article: Imaging low-energy positron beams in real-time with unprecedented resolution
Imaging low-energy positron beams in real-time with unprecedented resolution Open
Particle beams focused to micrometer-sized spots play a crucial role in forefront research using low-energy positrons. Their expedient and wide application, however, requires highly-resolved, fast beam diagnostics. We have developed two di…
View article: The influence of displacement damage on helium uptake and retention in tungsten
The influence of displacement damage on helium uptake and retention in tungsten Open
The influence of pre-existing displacement damage on the early stages of helium (He) interaction with tungsten (W) and the resulting defect creation was investigated experimentally. Samples were irradiated with 20.3 MeV W ions to different…
View article: Breakdown of Arrhenius law of temperature-dependent vacancy concentration in fcc lanthanum
Breakdown of Arrhenius law of temperature-dependent vacancy concentration in fcc lanthanum Open
We measured the temperature dependent equilibrium vacancy concentration using\nin-situ positron annihilation spectroscopy in order to determine the enthalpy\n$H_\\text{f}$ and entropy $S_\\text{f}$ of vacancy formation in elementary\nfcc-L…