arXiv subjects

Petra Specht

Publications and source records attributed to Petra Specht.

4 recordsLinked to original sources

arXiv2026

Role of self-coherence in single-electron phase contrast imaging

The extension of coherent lattice contrast into the energy loss region in high-resolution transmission electron microscopy (HRTEM) is described by a pulse-like electron-sample interaction in the energy/time uncertainty limit. It generates a wave packet by electron self-interference in any coherent-inelastic scattering event with energy loss. The width of this wave packet is characterized by a self-coherence length ls(ΔE) that is predictable because an intrinsic decoherence phase around one radian is set by the expectation value for phase fluctuations. In this case the visibility of interference contrast from a crystalline sample with lattice parameter a is limited by a Rayleigh-like transfer factor P(ls, a) in the self-coherently illuminated sample area. The model is verified by energy-filtered HRTEM images of hexagonal BN and identifies energy-loss-induced phase noise as a single-electron visibility limit distinct from resolution limitations caused by ensemble-coherence or counting-statistical noise.

cond-mat.mtrl-sci↗

arXiv2024

Realtime observation of a tungsten-promoted size regulation mechanism in a rhodium catalyst at atomic resolution

The static and genuine structure of small rhodium and rhodium/tungsten nanoparticles on an alumina support can be imaged with atomic resolution even if single digit atom clusters are investigated. Low dose rate electron microscopy is key to the achievement and can generally be applied to investigate any similar material. In such conditions it becomes feasible to identify the chemical composition of nanocrystals from quantitative contrast analyses alone by counting atoms. The ability to fully characterize an unaltered, initial state of the objects allows targeting structural excitations or conformational changes induced by the electron beam itself. For the specific case of catalytic Rh:W particles we stimulate a tungsten-promoted size regulation mechanism in real time that is driven by Oswald ripening and can be understood by a strong binding of tungsten atoms to the oxygen atoms of the support, which builds up strain as the cluster sizes increase.

cond-mat.mtrl-sci↗

arXiv2024

Single electron self-coherence and its wave/particle duality in the electron microscope

Intensities in high-resolution phase-contrast images from electron microscopes build up discretely in time by detecting single electrons. A wave description of pulse-like coherent-inelastic interaction of an electron with matter is detailed and verified. In perspective, the interaction time of any matter wave compares with the lifetime of a virtual particle of any elemental interaction, suggesting the present concept of coherent-inelastic interactions of matter waves might be generalizable.

cond-mat.mtrl-sci↗

arXiv2022

Direct evidence of a continuous transition between waves and particles

The correlation between particle and wave descriptions of electron-matter interactions is analyzed by measuring the delocalization of an evanescent field using electron microscopy. Its spatial extension coincides with the energy-dependent, self-coherence length of propagating wave packets that obey the time-dependent Schrödinger equation and undergo a Goos-Hänchen shift. In the Heisenberg limit they are created by self-interferences during coherent-inelastic Coulomb interactions with a decoherence phase Δϕ = 0.5 rad and shrink to particle-like dimensions for energy losses of more than 1000 eV.

quant-ph↗