Their research revealed that surface-adsorbed oxygen acts as a shallow trap state limiting electronic performance of BiVO 4 thin films. Furthermore, they used complementary pc-AFM and in-situ Kelvin probe measurements to elucidate the influence of chemical interactions of adsorbed oxygen and water on charge transport and interfacial charge transfer of photogenerated charge carriers. For the first time, they showed that the charge transport in BiVO 4 photoanodes can be described by the space-charge-limited current model in the presence of trap states. Specifically, they revealed the critical impact of (i) contact formation between the nanoscale probe and the semiconductor, and of (ii) chemical environment on nanoscale transport measurements of PEC devices. Toma and Eichhorn recently performed quantitative analysis of sub-pA photocurrent maps and IV-curves obtained with their Dimension Icon AFM. Johanna Eichhorn will then focus on the nanoscale characterization of BiVO 4 – a highly interesting semiconductor light absorber for solar water splitting. Francesca Toma will give a short overview of the ongoing research projects on solar energy conversion in her group. Established AFM methods, either provide property maps at discrete frequencies orders of magnitude higher than bulk measurements (e.g., TappingMode and contact resonance), making comparisons difficult, or struggle with such intrinsic mechanical properties as loss tangent and storage modulus (e.g., force spectroscopy and PeakForce Tapping). Where DMA is well suited for measurements on bulk samples, it is less adept at characterizing microscopic domains within heterogeneous polymer material.
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Since the mechanical properties of polymers are time dependent, full understanding requires measurements over a range of frequencies and temperatures. This webinar introduces the polymer rheological measurement capabilities of the new AFM-nDMA mode, which for the first time provides viscoelastic measurements that match bulk dynamic mechanical analysis (DMA) over the entire frequency range. Webinar: Measuring Nanoscale Viscoelastic Properties with AFM-Based nano-DMA
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