Physicists find a new way to measure the properties of a material’s surface layer

 

International Conference on Nuclear Physics





Using a process called auger-mediated positron sticking (AMPS), scientists from the Positron Lab in the UTA Department of Physics have developed a new technique that can measure the properties of the topmost atomic layer of materials.






This novel spectroscopic tool uses virtual photons to measure the topmost atomic layer’s electronic structure selectively. When incoming positrons change from vacuum states to bound surface states on the sample surface, they produce virtual photons with the energy to excite electrons into the vacuum.

The short interaction range of the virtual photons restricts the penetration depth to approximately the Thomas-Fermi screening length. Measurements and analysis of the kinetic energies of the emitted electrons made on a single layer of graphene deposited on Copper and the clean Copper substrate show that the ejected electrons originate exclusively from the topmost atomic layer.

Alex Weiss, professor, and chair of the UTA Department of Physics, said, “We figured out how to use this phenomenon that we discovered in 2010 to measure the top layer and get information about the electronic structure and the behavior of the electrons in the top layer. That will determine a material’s many properties, including conductivity, and can have important implications for building devices.”



Alex Fairchild, a postdoctoral scholar in the Positron Lab, the study’s lead author, said, “The AMPS process is unique because it uses virtual photons to measure the topmost atomic layer.”

“This differs from typical techniques like photoemission spectroscopy, where a photon penetrates multiple layers into the bulk of a material and therefore contains the combined information of the surface and subsurface layers.”

Varghese Chirayath, assistant research professor, said, “Our AMPS results showed how virtual photons emitted following positron-sticking interact preferably with electrons that extend further into the vacuum than with more localized electrons to the atomic site. Our results are thus essential to understand how positrons interact with surface electrons and are extremely important to understand other similarly surface-selective, positron-based techniques.”

Weiss noted that the UTA Positron Lab is currently the only place this technique could have been developed due to the capabilities of its positron beam.

“UTA probably has the only lab in the world that has a positron beam that can get down to the low energies needed to observe this phenomenon.”



#SurfaceLayer: The general hashtag for discussing and exploring various aspects of surface layers.
#MaterialsScience: Pertaining to the study of materials and their properties, including surface layers.
#Coatings: Discussing different types of coatings and their applications in surface layers.
#SurfaceTreatment: Focusing on processes and techniques used to modify and enhance surface layers of materials.
#ThinFilms: Exploring the science and applications of thin films that form surface layers.
#SurfaceChemistry: Discussing the chemical processes and reactions that occur at the surface layer of materials.
#CorrosionProtection: Pertaining to methods and materials used to protect surfaces from corrosion and degradation.
#SurfaceAnalysis: Exploring techniques and methodologies for characterizing and analyzing surface layers.
#SurfaceEngineering: Discussing the design and development of functional surface layers with specific properties and functionalities.
#SurfaceModification: Focusing on techniques used to alter the properties and behavior of surface layers.
#SurfaceCoatingTechnology: Exploring advancements and innovations in coating technologies for surface layers.
#SurfaceProperties: Discussing the physical, chemical, and mechanical properties of surface layers.

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