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Reliable Work Function Determination of Multicomponent Surfaces and Interfaces: The Role of Electrostatic Potentials in Ultraviolet Photoelectron Spectroscopy
Author(s) -
Schultz Thorsten,
Lenz Thomas,
Kotadiya Naresh,
Heimel Georg,
Glasser Gunnar,
Berger Rüdiger,
Blom Paul W. M.,
Amsalem Patrick,
de Leeuw Dago M.,
Koch Norbert
Publication year - 2017
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201700324
Subject(s) - work function , x ray photoelectron spectroscopy , materials science , kelvin probe force microscope , work (physics) , spectral line , ultraviolet photoelectron spectroscopy , ultraviolet , electron , spectroscopy , chemical physics , molecular physics , energy (signal processing) , secondary electrons , function (biology) , atomic physics , analytical chemistry (journal) , nanotechnology , atomic force microscopy , physics , chemistry , optoelectronics , thermodynamics , nuclear magnetic resonance , quantum mechanics , layer (electronics) , evolutionary biology , biology , chromatography
Abstract Ultraviolet photoelectron spectroscopy (UPS) is a key technique to determine the work function (Φ) of surfaces by measuring the secondary‐electron cut‐off (SECO). However, the interpretation of SECO spectra as obtained by UPS is not straightforward for multicomponent surfaces, and it is not comprehensively understood to what extent the length scale of inhomogeneity impacts the SECO. Here, this study unravels the physics governing the energy distribution of the SECO by experimentally and theoretically determining the electrostatic landscape above surfaces with defined patterns of Φ. For such samples, the measured SECO spectra exhibit actually two cut‐offs, one representing the high Φ surface component and the other one corresponding to an area‐averaged Φ value. By combining Kelvin probe force microscopy and electrostatic modeling, it is quantitatively demonstrated that the electrostatic potential of the high Φ areas leads to an additional energy barrier for the electrons emitted from the low Φ areas. Theoretical predictions of the induced energy barrier dependence on the Φ‐pattern length scale and sample bias are further experimentally verified. These findings establish a solid base for reliable SECO interpretation of heterogeneous surfaces and improved reliability of interfacial energy‐level diagrams from UPS experiments.