Event
Beyond Chemical Composition Part II: Best Practices for Optimizing LEIPS, UPS, and REELS Experiments
Presented by Dr. James Johns
Modern surface analysis tools are typically multi-purpose instruments, equipped with a wide range of options enabling the measurement or characterization of many distinct surface properties. For example, X-ray photoemission spectrometers (XPS) are often additionally equipped with instrumentation designed to measure the valence electronic structure. These additional options enable scientists and engineers to acquire complementary information from samples at the same location without having to expose sensitive samples to the air, saving significant time and money over measurements acquired on separate tools.
In Part 2 of this webinar series, James will continue the discussion of three of these techniques available on PHI XPS products: Ultraviolet Photoemission Spectroscopy (UPS), Low Energy Inverse Photoemission Spectroscopy (LEIPS), and Reflection Electron Energy Loss Spectroscopy (REELS). UPS and LEIPS are powerful techniques for measuring the occupied valence and unoccupied conduction electronic bands of a material/surface, including beam-sensitive materials that can be damaged by other conventional methods. REELS, meanwhile, uses an electron beam to probe the optical excitations that can happen at a surface, and additionally is capable of measuring hydrogen content.
Here, he will talk about the specifics of designing an experiment for each of these three techniques and provide guidelines for sample handling and preparation to maximize the signal to noise and data quality for these techniques. Special attention will be given to the role of sample charging and the way in which the typical current densities for each experiment affect which samples are appropriate. James will also discuss the workflow of UPS/LEIPS/REELS experiments, focusing on effective and efficient integration with traditional XPS analysis quantifying atomic composition and chemical states. Balancing the speed of data acquisition with the required collection time for acquiring high quality data can be challenging for new users of a technique, and he will discuss a framework for helping users find that ideal balance for their own samples and goals. He will discuss some of the most common reasons and conditions where each of these techniques may give unexpected or erroneous results, and how users can spot and avoid them.
Finally, end the webinar by going through the data analysis of an example for each of these techniques. Because the spectra for these techniques are different from typical XPS spectra, they require different tools for proper analysis. James outline the process of transforming raw spectra to physical properties of a system such as the electron affinity (EA), ionization potential (IP), band gap (electronic and optical) and work function. By the end of this webinar, viewers will be equipped with the knowledge to determine when these techniques are appropriate and how to use them to reliably measure their own materials.
