Quantification of Sample Thickness and In-Concentration of InGaAs Quantum Wells by Transmission Measurements in a Scanning Electron Microscope

Abstract

High-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) images of electron-transparent samples show dominant atomic number (Z-) contrast with a high lateral resolution. HAADF STEM at low electron energies <30 keV is applied in this work for quantitative composition analyses of InGaAs quantum wells. To determine the local composition, normalized experimental image intensities are compared with results of Monte Carlo simulations. For verification of the technique, InGaAs/GaAs quantum-well structures with known In concentration are used. Transmission electron microscopy samples with known thickness are prepared by the focused-ion-beam technique. The method can be extended to other material systems and is particularly promising for the analysis of materials that are sensitive toward knock-on damage.

Low-energy electron scattering in carbon-based materials analyzed by scanning transmission electron microscopy and its application to sample thickness determination

“…Alternatively, low keV STEM intensities can be modelled by MC simulations (Merli et al ., 2003; Volkenand et al ., 2010), which is well established for samples with higher atomic numbers. Statistically relevant results are obtained by applying suitable differential cross‐sections to a large number of electrons subjected to several/multiple scattering processes and calculating their trajectories through the sample.…”

“…(2003; Morandi & Merli, 2007) used low keV to analyze dopant profiles in semiconductors. Volkenand et al . (2010) applied low keV STEM to determine the thickness of a GaAs TEM sample and the composition of InGaAs in an InGaAs/GaAs heterostructure by comparing experimental low keV STEM data with the results of Monte Carlo (MC) simulations.…”

Quantitative Analysis of HAADF–STEM Images of MoVTeTaO M1 Phase Catalyst for Propane Ammoxidation to Acrylonitrile

“…High‐angle annular dark‐field (HAADF) scanning transmission electron microscopy (STEM) has been widely employed as one of the most important imaging techniques for the direct analysis of interfaces, structures, and chemical compositions in materials because the contrast in HAADF–STEM images is highly sensitive to the atomic number ( Z ) of scattering species and, therefore, is relatively simple to interpret . Given the capability of the HAADF–STEM imaging technique to provide the details of atomic structure with sub‐angstrom resolution, Pyrz et al.…”

Application of low-energy scanning transmission electron microscopy for the study of Pt-nanoparticle uptake in human colon carcinoma cells

“…By contrast, low-energy HAADF STEM imaging is not affected by Bragg diffraction-induced contrast variations, which is an indispensable prerequisite for quantification of the image intensity. Quantification of HAADF STEM contrast was indeed already successfully shown for solid-state samples (Volkenandt et al 2010). Besides this quantitative aspect, the authors emphasise several advantages of low-energy HAADF STEM compared with standard TEM techniques.…”

“…The simulations yield the angular and energy distribution of the electrons leaving the sample. The HAADF intensity corresponds to the total number of transmitted electrons in the angular range covered by the real HAADF detector segment which has to be corrected for the properties of the detection system (Volkenandt et al 2010). For example, some electrons, which impinge on the HAADF detector, are backscattered and do not contribute to the measured image intensity.…”