Advanced van der Waals (vdW) heterostructure devices rely on the incorporation of high quality dielectric materials which need to possess a low defect density as well as being atomically smooth and uniform. In this work we explore the use of talc dielectrics as a potentially clean alternative substrate to hexagonal boron nitride (hBN) for few-layer transition metal dichalcogenide (TMDC) transistors and excitonic TMDC monolayers. We find that talc dielectric transistors show small hysteresis which does not depend strongly on sweep rate and show negligible leakage current for our studied dielectric thicknesses.
View Article and Find Full Text PDFThe fine structure of exciton states in colloidal quantum dots (QDs) results from the compound effect of anisotropy and electron-hole exchange. By means of single-dot photoluminescence spectroscopy, we show that the emission of photoexcited InP/ZnSe QDs originates from radiative recombination of such fine structure exciton states. Depending on the excitation power, we identify a bright exciton doublet, a trion singlet, and a biexciton doublet line that all show pronounced polarization.
View Article and Find Full Text PDFGlycosyl cations are crucial intermediates formed during enzymatic and chemical glycosylation. The intrinsic high reactivity and short lifetime of these reaction intermediates make them very challenging to characterize using spectroscopic techniques. Herein, we report the use of collision induced dissociation tandem mass spectrometry to generate glycosyl cations in the gas phase followed by infrared ion spectroscopy using the FELIX infrared free electron laser.
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