Biomedical subjects

H Kirmse

Publications and source records attributed to H Kirmse.

11 recordsLinked to original sources

PubMed2006

Quantitative high resolution transmission electron microscopy of nanostructured semiconductors.

Peak-finding procedures and the geometric phase method of quantitative high resolution electron microscopy (qHRTEM) were applied to determine the local strain and the chemical composition of nanostructured semiconductor materials. The growth of the structures investigated was induced by minimization of strain energy. The analysis of strain distribution is necessary for the understanding of the self-organized formation of nanostructures. The possibilities and limitations of the methods are discussed in detail by analysing HRTEM images of (Si,Ge) islands and of a double layer of stacked quantum dots of (In,Ga)As and Ga(Sb,As).

Journal Article↗

PubMed2000

Electron microscope characterization of CdSe/ZnSe quantum dots based on molecular dynamics structure relaxations

Molecular dynamics simulations using empirical potentials are applied to characterize the structure, the energy relaxation and the stability of pyramidal-shaped quantum dots in the CdSe/ZnSe system. The relaxed structure models are used for a reliable interpretation of electron microscope investigations to analyze the size, the shape and the strain fields of the quantum dots. Though the elastic strains modify the electron microsope image contrast by creating virtual truncations of the pyramids or additional black-white lobes, optimum imaging conditions chosen will reveal the shape and the size of the dots.

Journal Article↗

PubMed1999

TEM characterization of self-organized CdSe/ZnSe quantum dots.

CdSe quantum dots (QDs) grown on ZnSe were investigated by various transmission electron microscopy (TEM) techniques including diffraction contrast imaging, high-resolution and analytical transmission electron microscopy both of plan-view as well as cross-section specimens. The size of the QDs ranges from about 5-50 nm, where from the contrast features in plan-view imaging two classes can be differentiated. In the features of the smaller dots there is no inner fine structure resolvable. The larger ones exhibit contrast features of fourfold symmetry as expected for pyramid-like islands. Corresponding simulations of diffraction contrast images of truncated CdSe pyramids with the edges of the basal plane orientated parallel to <100> are in relatively good agreement with this assumption. In TEM diffraction contrast imaging of cross-section samples the locations of the quantum dots are visualized by additional dark contrast features. The QDs have a distinct larger extension in growth direction compared to the almost uniformly thick CdSe wetting layer. The presence of the CdSe QDs was also confirmed by energy-dispersive X-ray spectroscopy.

Journal Article↗

PubMed1987