RESUMEN
Intercalation forms heterostructures, and over 25 elements and compounds are intercalated into graphene, but the mechanism for this process is not well understood. Here, the de-intercalation of 2D Ag and Ga metals sandwiched between bilayer graphene and SiC are followed using photoemission electron microscopy (PEEM) and atomistic-scale reactive molecular dynamics simulations. By PEEM, de-intercalation "windows" (or defects) are observed in both systems, but the processes follow distinctly different dynamics. Reversible de- and re-intercalation of Ag is observed through a circular defect where the intercalation velocity front is 0.5 nm s-1 ± 0.2 nm s.-1 In contrast, the de-intercalation of Ga is irreversible with faster kinetics that are influenced by the non-circular shape of the defect. Molecular dynamics simulations support these pronounced differences and complexities between the two Ag and Ga systems. In the de-intercalating Ga model, Ga atoms first pile up between graphene layers until ultimately moving to the graphene surface. The simulations, supported by density functional theory, indicate that the Ga atoms exhibit larger binding strength to graphene, which agrees with the faster and irreversible diffusion kinetics observed. Thus, both the thermophysical properties of the metal intercalant and its interaction with defective graphene play a key role in intercalation.
RESUMEN
Analyzing and interpreting the nanoscale morphology of semiconducting polymers is one of the key challenges for advancing in organic electronics. The orientation persistence length (OPL) as a tool to analyze orientation maps generated by photoemission electron microscopy (PEEM) - a state of the art tool for nanoscale imaging/spectroscopy - is presented here. The OPL is a way to quantify the chain orientation within the polymer film in a single graph. In this regard, it is a convincing method that will enable additional direct correlations between the chain orientation and electrical or optical parameters. In this report, we provide computational insights into the factors that contribute to the OPL.
RESUMEN
Only rigorous understanding of the relationship between the nanoscale morphology of organic thin films and the performance of the devices built from them will ultimately lead to design rules that can guide a structured development on the field of organic electronics. Despite great effort, unraveling the nanoscale structure of the films is still a challenge in itself. Here we demonstrate that photoemission electron microscopy can provide valuable insights into the chain orientation, domains size and grain boundary characteristics of P3HT films spun cast from different solvents at room as well as at elevated temperatures.
RESUMEN
Photoemission electron microscopy in combination with polarized laser light is presented as a tool permitting direct imaging of polymer-chain orientation and local degree of order in semicrystalline samples of semiconducting polymers, a promising class of materials for future electronics. The key advantages of this imaging tool are its nondestructive and fast measurements, straightforward data analysis, the low complexity of sample preparation, and the possibility of performing measurements on a broad variety of technologically relevant substrates. The high spatial resolution of the microscope provides insights into the nanoscale morphology, which is relevant for the material's performance in electronic devices.
