TY  - JOUR
AB  - Relativistic forward scattering of electrons at finite temperature involves the incoherent superposition of diffraction patterns formed by different snapshots of thermal atomic displacements. In experiments, thermal vibrations lead to thermal diffuse scattering (TDS), partly dominating diffraction patterns of thick specimens. This study sheds light on the effects of TDS on solutions to the inverse scattering problem using combined realand diffraction-space information acquired in a scanning transmission electron microscope (STEM) to retrieve the object's phase. Using frozen phonon multislice within the Einstein approximation, realistic ground truth data of 20-nm-thick SrTiO3 is generated and subjected to contemporary inverse multislice schemes to retrieve the projected Coulomb potential slicewise. We first classify phase retrieval algorithms as to their assumptions on periodicity along the incident beam direction, as well as pixelwise and parametrized reconstruction methods. It is found that pixelwise object reconstructions are capable of retrieving structural details qualitatively while being prone to contain TDS-related artifacts which can result in unphysical potentials. For pixelwise reconstructions of multiple independent specimen slices, we observe that the origin of TDS, i.e., thermal atomic displacements, starts to emerge naturally. However, the quantitative assessment tends to too small mean squared thermal displacements, also when reconstructing multiple object modes. Using an atomistically parametrized inversion strategy which exploits the explicit separation of thermal vibrations and potentials, temperature and chemistry of the specimen can be retrieved quantitatively with high accuracy.
AU  - Herdegen, Z.*
AU  - Diederichs, B.
AU  - Mueller-Caspary, K.*
C1  - 71579
C2  - 56134
CY  - One Physics Ellipse, College Pk, Md 20740-3844 Usa
TI  - Thermal vibrations in the inversion of dynamical electron scattering.
JO  - Phys. Rev. B Condens. Matter
VL  - 110
IS  - 6
PB  - Amer Physical Soc
PY  - 2024
SN  - 0163-1829
ER  - 

TY  - JOUR
AB  - The mean attenuation length, L, of electrons emitted from ion bombarded solids was derived from measured angular-dependent electron yields γ(θ) in combination with Monte Carlo simulations of inelastic (electronic) energy deposition. The transport controlled contributions of excited electrons to the measured electron yields were derived as the integral gL over Seexp(-z/L), where Se(θ,z) is the electronic energy deposition and z the depth from the surface. The unknown attenuation length L≡L reflects the average over the energy spectrum and the angular distribution of those internally excited electrons that can reach the solid-vacuum interface and overcome the surface barrier. To determine L, the ratios gL(θ)/gL(0), calculated for 0≤L≤10nm, were compared with measured yield ratios γ(θ)/γ(0) for a wide variety of projectile-target combinations and impact energies between 1 and 50 keV (velocity-proportional electronic stopping). The procedure works well at angles at which Se(θ,z) decreases smoothly in the depth region between 1 and 3 nm. The result is L=1.5±0.3 nm, a number basically in accordance with expectation based on estimated data for the inelastic mean free path of low-energy electrons (<25 eV) but a factor of 10 lower than the numbers recently advocated (10-15 nm) to rationalize "internal" electron yields observed with metal-insulator-metal sandwich structures.
AU  - Wittmaack, K.
C1  - 44423
C2  - 36920
CY  - College Pk
TI  - Attenuation length in ion-induced kinetic electron emission: A key to an understanding of angular-dependent yields.
JO  - Phys. Rev. B Condens. Matter
VL  - 91
IS  - 11
PB  - Amer Physical Soc
PY  - 2015
SN  - 0163-1829
ER  - 

TY  - JOUR
AU  - Wittmaack, K.
C1  - 9944
C2  - 21465
SP  - 235211/1-235211-11
TI  - Analytical description of the sputtering yields of silicon bombarded with normally incident ions. 
JO  - Phys. Rev. B Condens. Matter
VL  - 68
PY  - 2003
SN  - 0163-1829
ER  -