PROBING ORDERING AT SOLID-LIQUID INTERFACES BY IN-SITU ABERRATION CORRECTED HIGH RESOLUTION TEM

Knowledge of the nature of solid-liquid interfaces is important both for fundamental science and for many technological processes. Many theoretical and experimental approaches have been used during the last few decades to study various solid-liquid interfaces. These studies have predicted the presence of some ordering in the liquid adjacent to the crystal. However, only recently experimental measurements were successfully correlated with theoretical approaches to confirm that the observed ordering in the liquid is not an experimental artifact [[i]].

The tremendous progress in the field of transmission electron microscopy during the last two decades provides a technique for direct investigation of complex structures such as solid-liquid interfaces, and the ability to extract from such interfaces quantitative and highly reliable information (i.e. significantly reducing imaging artifacts). However, residual artifacts that originate from the experimental conditions (i.e. high temperature causing thermal vibrations and specimen drift) may still cause erroneous interpretation of the data. To overcome these limitations a new software program, named High Resolution Electron Microscopy Digital Image Matching Analysis (HREM-DIMA [[ii]]), was developed.

HREM-DIMA is based on iterative digital image matching of various model structures by comparison of the experimental image contrast to that obtained from multi-slice image calculations [[iii]]. This software combines an interactive iterative matching process, done via a very intuitive graphical user interface (GUI), and a fully quantitative process of comparison between experimental and simulated micrographs. Fully quantitative results which can be obtained by this approach, providing at high precision the conditions at which the experimental data was acquired and ultimately the positions of the projected atomic columns in the specimen.

In the current study, ordering in liquid Al in contact with crystalline alumina was investigated using a Cs corrected FEI Titan 80-300 scanning/transmission electron microscope (S/TEM). The samples were mounted on a Gatan double tilt holder equipped with a built-in furnace which allowed heating the samples up to 1000°C. HREM-DIMA and other image analysis methods were used to extract quantitative information on the degree of ordering at the Al-Al₂O₃liquid-solid interfaces.