| AVS 63rd International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuP |
| Session: | Applied Surface Science Division Poster Session |
| Presenter: | Vincent Smentkowski, General Electric Global Research Center |
| Authors: | V. Smentkowski, General Electric Global Research Center L. Le Tarte, GGeneral Electric Global Research Center H. Piao, General Electric Global Research Center M. Marko, Wadsworth Center |
| Correspondent: | Click to Email |
Many types of phase-shifters have been developed for use in place of the TEM objective aperture. The phase shifters act to increase phase contrast by providing high transfer of information over a very wide spatial-frequency range. Unfortunately, many of these devices fail shortly after being installed into the instrument due to charging in the electron beam, so we have been experimenting with surface deposition of novel thin-film metals. In some cases, it is essential that the electron-scattering cross-section of the metal film be as small as possible, so the films must often be quite thin (less than 10 nm thick). Accurate analysis of such thin films is required to understand the composition of the layers, unexpected impurities both in the films and at the interfaces, the oxidation state of the layers, and the lateral uniformity of the layers.
In this poster we use a suite of surface analysis techniques to monitor the distribution of species through one multilayer phase plate stack comprised of 2nm Rh, 6nm C, and 2nm Al using depth profiling protocol. The pros and cons of each of the surface analysis techniques are illustrated via the sample analyzed. Each of the three techniques used here were able to successfully identify and resolve each of the 3 layers with a sufficient number of data points defining the thin layers. Each of the techniques also revealed oxygen in the aluminum layer with a stoichiometry of about Al2O3.
An advantage of ToF-SIMS for depth profiling is the ability to rapidly collect an image at every depth, allowing for 3D rendering of the data sets. The 3D ToF-SIMS renderings do not reveal discontinuous regions at a length scale of a few hundred nm (the conditions used here); ruling out holes at a length scale of less than a few hundred nanometers in the Rh layer would require ToF-SIMS analysis using a pulsing mode with a smaller analytical spot size. Another advantage of ToF-SIMS is that a full mass spectrum is saved at every voxel and hence all elements and high mass molecular fragments are analyzed. Often unexpected species are revealed sub surface. A disadvantage of ToF-SIMS is the ion yield varies depending on the composition of the matrix and this makes quantitative analysis more difficult. In contrast sensitivity factors have been developed for both AES and XPS and these reported sensitivity factors are typically valid to within 10% and hence quantitative analysis is easier.
Mike Marco acknowledges funding through NIH grant GM103555.