Above and Beyond – Enabling Next Generation Devices by Novel Material
Characterization Approaches
Dr. Mirko Weidner
SPECS Surface Nano Analysis GmbH, Berlin
The performance of modern optoelectronic devices is in most cases restricted by the physical
limits of the materials forming distinct functional layers. Next generation devices are,
therefore, often heralded by the elimination of a long standing limit to material performance,
or the introduction of a wholly novel material; a relevant example being the introduction of
IGZO (In-Ga-Zn-O) into modern display technology. These advances are, as often as not,
driven by new material characterization techniques, enabling scientists to better understand
the detrimental physical effects they are trying to eliminate.
Photoelectron spectroscopy has proven to be a powerful tool in this regard, time and time
again: it is the only technique that enables direct measurement of a material’s electronic
structure, revealing elemental oxidation states, valence band structures and Fermi Level
position, all of which are highly relevant properties in a TCM. Due to its extreme surface
sensitivity, the method also allows the direct and indirect characterization of thin film
interfaces, which are known to be crucial for the performance of electronic devices of any
kind.
Breaking down existing performance barriers also hinges on advancing tried and tested
characterization techniques, such as photoelectron spectroscopy. This talk will focus on the
recent advances made in this field, with a particular focus on the topic of near-ambient-
pressure XPS (X-ray Photoelectron Spectroscopy), which lifts the strict limitation of UHV
conditions. This enables scientists to measure under previously unattainable conditions, e.g.
measuring liquid or biological samples, as well as exposing solids to gaseous or liquid phase
in order to simulate device working conditions. In regard to TCM research, this opens up
exciting new possibilities such as: in-operando measurements of TiO
2
photocatalysts, water
splitting devices or environmental sensors; live monitoring of the annealing-induced changes
in wet-chemically processed TCM films; measuring solid-liquid interfaces for applications
such as electrochromic windows or other transparent devices containing liquid electrolytes.
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