Abstract
Silicon is widely used in (opto-)electronics devices, despite displaying fundamental downfalls such as an indirect band gap. As a result, substantial research efforts have been placed in finding novel materials that could suitably replace silicon on various electronic device applications. These novel material systems, here labelled as emerging electronics, exhibit critical nanoscale structure-function relationships that introduce measurement challenges additional to those successfully employed in silicon-based metrology. One important aspect is the need to characterise nanostructural inhomogeneities, which can determine device performance as well as operational stability.
The present research focuses on employing scanning probe microscopy as a versatile ‘one-instrument’ approach for reliable and quantitative measurements on emerging electronics. With the focus lying on employing both electrical and tip-enhanced optical spectroscopic modes, their practical implementation is discussed. Combined modes of scanning probe microscopy are subsequently applied to study the effect of grain boundaries on the functional performance in organic-inorganic halide perovskites for photovoltaic applications. Beneficial charge separating properties due to local band bending are found to compete with detrimental increased carrier recombination, highlighting the critical role of the microstructure. Following, the intrinsic instability and degradation pathways of perovskite films under simulated operational conditions are spatially resolved. Decomposition effects are locally resolved and attributed to inhomogeneous charge redistribution effects under operational stresses. Finally, moving towards the study of device architectures, the electrical contact in two-dimensional material heterostructures is characterised. Absence of Fermi level pinning is demonstrated alongside the presence of a vertical interface dipole, which governs charge transfer and carrier relaxation pathways.
Results of this research contribute novel findings in the current understanding of important mechanisms limiting industry uptake of emerging electronics. In addition, the multi-parameter approach to scanning probe microscopy is demonstrated as a powerful tool for investigation of measurement challenges related to emerging electronic systems.