Impact of PHI Auger instruments on scientific discoveries

Review by Staff Scientist Ashley Maloney

High-quality research publications are at the cornerstone of scientific advancement, understanding, and communication. Here, we review the year 2021 and the impact that the Physical Electronics Auger Electron Spectroscopy (AES) instrument has had in supporting scientific breakthroughs.

Over 1300 scholar publications, including peer-reviewed articles and book chapters, have been published in 2021 using PHI AES instruments, many of which were published in high-impact journals (Nature and Science group).

PHI AES instruments were used to study a large range of materials for applications of high technological and research importance - solar cells based on perovskites1, gallium arsenide2, and silicon3 ;  prosthesis and medical implants4-6; 2D materials for quantum electronic devices7; novel catalysts for fuel cells, water splitting, energy storage8-9, and the removal of organic micropollutants10; light emitting diodes11-12; thermoelectric materials13; deep-sea tribocorrosion of metal alloys14; low carbon steels for nuclear power plants and water-cooled reactors15; steel pitting corrosion16; additive manufacturing17; lithium-ion batteries18-19; and all solid-state batteries20.

One paper published this year in Nature Communications as a collaborative study led by the National Engineering Laboratory for Industrial Wastewater Treatment at the East China University of Science and Technology is of impressive scientific merit. This work demonstrates the viability of a naturally abundant Fe/Mn-based catalyst to boost the future development of biomass products such as biofuel and enhance plastics degradation and wastewater treatment. Using the PHI 710 Scanning Auger Nanoprobe, Wang and coworkers21 mapped the fresh and used Mn-based catalyst with a sub-micron spatial resolution to elucidate the mechanism of catalyst oxidation (Figure 1). High spatial resolution (<8 nm) elemental mapping using the PHI 710 instrument enabled superior visualization of this highly topographic material.

Figure 1: Scanning Auger mapping of Mn of fresh (bottom) and used (top) MnO2/Goe catalyst

Another esteemed paper published this year in NPG Asia Materials by Haindl and coworkers22 at the Tokyo Institute of Technology and the University of Glasgow utilizes the PHI 710 Auger instrument to study Fe-based superconductors. In this work, the interface chemistries of Fe-pnictide heterostructure layered materials were probed via Auger depth profiling. The Auger depth profiles reveal smooth and clean interfaces in undoped and Co2+ substituted cases, and an interface layer formation present in the case of excess O2- during deposition (Figure 2). The ability to precisely depth profile these extremely thin layers highlights the capabilities of the monoatomic Ar+ ion gun equipped on the PHI 710 and demonstrates minimal sputter mixing and enhanced depth resolution.

Figure 2: STEM images of a. clean, undoped Sm-1111/Ba-122 interface, b. clean, Co2+-substituted La-1111/Ba-122interface; c. interface layer (IFL) formation in Sm-1111/Ba-122 with excess O2–.  AES depth profiles across the interface for d. undoped Sm-1111/Ba-122, e. Co2+-substituted La-1111/Ba-122, and f. Sm-1111/Ba-122 with excess O2–.

A third high-impact publication this year in Electrochemica Acta by Zhao and coworkers23 uses the PHI 710 Scanning Auger Nanoprobe to study Na-ion battery materials. In this work, the stability and performance of Na-ion battery technology was enhanced via surface modification of sodium manganese hexacyanoferrate (NaMnHCF) as a cathode material. Auger spectroscopy was used to analyze the in-depth chemical composition of the modified surface. The spectra reveal an increase in Cu composition and a decrease in Mn composition after sputtering ~20 nm into the material. This modification significantly improves the long-term stability of the electrode.

Figure 3: In-depth AES spectra of Mn and Cu on a microscale grain of NaMnHCF after the ion-exchange modification.

Physical Electronics is proud of the role the PHI 710 Scanning Auger Nanoprobe has played in achieving such prestigious scientific advancements over this past year. Please visit the citations below for more details regarding the studies mentioned in this article.

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© 2022 Physical Electronics, Inc. (PHI) All Rights Reserved.