Article

Ensuring successful experiments when moving beyond XPS: a comparison of the experimental requirements for LEIPS, UPS, and REELS

Surface Analysis Spotlight: XPS

by James Johns Staff Scientist

The powerful techniques of surface science have been utilized for nearly a century to probe the chemical and physical properties of the materials and interfaces, which undergird virtually all modern technologies.  For most of its history, the chemical and physical sides of surface science have been divided by the level of expertise and specialization required to operate instrumentation and analyze results from their respective domains.  Commercial instrumentation analyzing the atomic composition of surfaces and the chemical state of surface atoms has existed for over 50 years since Physical Electronics (PHI) and Kratos (AEI) introduced commercial Auger and XPS instruments in 1969.   And while the tools to characterize the physical and electronic properties of surfaces have existed for a similar amount of time, they had largely been domain of specific labs who specialize in specific measurement techniques.

Driven by advances in combinatorial sciences, photovoltaics, new materials for batteries, and the incorporation of new materials beyond silicon into the semiconductor industry, the range of scientists and engineers wanting to know the electronic structure of surfaces and interfaces has grown exponentially over the past decade.  Instrument manufacturers have correspondingly developed multipurpose tools combining chemical analysis with an array of powerful tools for surface electronic structure measurements.  PHI Genesis, the latest evolution in this line of powerful surface science instruments from Physical Electronics, combines cutting-edge chemical and physical analysis with the modern convenience of automated sample introduction, SEM-like point & click navigation, and user-friendly software for automating experimental analysis.  In short, it has never been easier for scientists and engineers with a broad range of expertise to directly measure both the electronic and chemical structure of a material using a single instrument with multiple techniques all aimed at the same analysis position on the same sample.

Despite these measurements no longer being the sole domain of specialized experts, there are still experimental design guidelines that need to be considered to ensure that the data and the conclusions drawn from it are accurately capturing the information the user intends.  In my talk this November at the 2023 Fall AVS in Portland, Oregon, I will be discussing some strategies for experimental design when measuring the electronic structure of surfaces.  Focusing on Low Energy Inverse Photomission Spectroscopy (LEIPS), I will explain how the technique works, the type of samples which make for easier-to-interpret measurements, and how the technique compares to other techniques such as Reflection Energy Loss Spectroscopy (REELS) or electrochemical measurements.  In my talk, I'll also discuss the role of sample morphology, for example why nanoparticles can be so difficult to measure, and present some strategies for tackling pernicious surfaces and interfaces. At Physical Electronics, our goal is to enable scientists and engineers to solve increasingly complex problems by building accurate, sensitive, and user-friendly surface science instrumentation.

For more information on ensuring successful experiments when moving beyond XPS: a comparison of the experimental requirements for LEIPS, UPS, and REELS, please attend my AVS talk "Influence of Surface Structure and Electrostatics on Measuring Unoccupied Electronic States via Low Energy Inverse Photoemission Spectroscopy (LEIPS)", Tuesday, November 7 from 12-12:30pm.