Composition determination of semiconductor alloys towards atomic accuracy by HAADF-STEM.

This paper presents a comprehensive investigation of an extended method to determine composition of materials by scanning transmission electron microscopy (STEM) high angle annular darkfield (HAADF) images and using complementary multislice simulations. The main point is to understand the theoretical capabilities of the algorithm and address the intrinsic limitations of using STEM HAADF intensities for composition determination. A special focus is the potential of the method regarding single-atom accuracy.

Composition determination of multinary III/V semiconductors via STEM HAADF multislice simulations.

Knowledge of the microscopic elemental composition of multinary III/V semiconductor materials is crucial to the development of functionalized opto-electronic devices. Well-proven composition analysis methods, such as high resolution X-ray diffraction (HRXRD), fail to determine the elemental composition when more than three atomic species are involved. In this work we propose a procedure for the composition analysis of multinary III/V semiconductors at atomic resolution using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) image simulations.

Surface relaxation of strained Ga(P,As)/GaP heterostructures investigated by HAADF STEM.

The surfaces of thin transmission electron microscopy (TEM) specimens of strained heterostructures can relax. The resulting bending of the lattice planes significantly influences high-angle annular dark field (HAADF) measurements. We investigate the impact by evaluating the intensities measured at the atomic columns as well as their positions in high-resolution HAADF images.

Crystallization Caught in the Act with Terahertz Spectroscopy: Non-Classical Pathway for l-(+)-Tartaric Acid.

Crystal formation is a highly debated problem. This report shows that the crystallization of l-(+)-tartaric acid from water follows a non-classical path involving intermediate hydrated states. Analytical ultracentrifugation indicates solution clusters of the initial stages aggregate to form an early intermediate.

Influence of surface relaxation of strained layers on atomic resolution ADF imaging.

Surface relaxation of thin transmission electron microscopy (TEM) specimens of strained layers results in a severe bending of lattice planes. This bending significantly displaces atoms from their ideal channeling positions which has a strong impact on the measured annular dark field (ADF) intensity. With the example of GaAs quantum wells (QW) embedded in a GaP barrier, we model the resulting displacements by elastic theory using the finite element (FE) formalism.