Heat-induced transformation of CdSe–CdS–ZnS core–multishell quantum dots by Zn diffusion into inner layers

In this work, we investigate the thermal evolution of CdSe–CdS–ZnS core–multishell quantum dots (QDs) in situ using transmission electron microscopy (TEM). Starting at a temperature of approximately 250 °C, Zn diffusion into inner layers takes place together with simultaneous evaporation of particularly Cd and S. As a result of this...

Atomic Resolution Monitoring of Cation Exchange in CdSe-PbSe Heteronanocrystals during Epitaxial Solid?Solid?Vapor Growth

Here, we show a novel solid?solid?vapor (SSV) growth mechanism whereby epitaxial growth of heterogeneous semiconductor nanowires takes place by evaporation-induced cation exchange. During heating of PbSe-CdSe nanodumbbells inside a transmission electron microscope (TEM), we observed that PbSe nanocrystals grew epitaxially at the expense of CdSe...

Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering

The microstructure of the charge/orbital ordering Ruddleden-Popper phase PrCa2Mn2O7 was studied by transmission electron microscopy along both the [001] and the [110] orientation. Three coexisting charge/orbital ordering phases CO1, CO2, and CO3 were observed along the [001] orientation at room temperature. Different from the one-dimensional...

2D atomic mapping of oxidation states in transition metal oxides by scanning transmission electron microscopy and electron energy-loss spectroscopy

Using a combination of HAADF-STEM imaging and atomically resolved EELS in an aberration-corrected TEM we demonstrate the possibility of 2D atom by atom valence mapping in the mixed valence compound . The ELNES from and cation sites are similar to those of and references. Comparison with simulations shows that even though a local interpretation...

Surface decomposition of Pb2Sr2(Ca,Y)Cu3O8+? at room temperature studied with high-resolution electron microscopy

High-resolution electron microscopy shows that Pb2Sr2(Ca,Y)Cu3O8+? is sensitive to air at room temperature. Planar defects are induced by exposure to air. These planar defects are due to a depletion of Pb and Cu from the three-layer block: PbO-Cu?-PbO, ? being a vacancy. Once these blocks are depleted, further depletion is enhanced, leading to...