High resolution electron microscopy of molecular crystals I. Quaterrylene, C40H20

The polynuclear aromatic hydrocarbon quaterrylene, C40H20, has been studied by using high resolution electron microscopes operating at 100 and 500 kV. Despite the susceptibility of quaterrylene to damage by the incident electron beam, the use of low-dose techniques has allowed a detailed investigation of thin film growth and grain boundary structure in quaterrylene. Comparisons with image simulations establish that high resolution images recorded in the (110)-projection at 500 kV extend to about 0.35 nm, with this figure being limited by radiation damage rather than microscope performance. Moreover, critical dose measurements by electron diffraction establish a good correlation between dose and spot resolution. Extensive crystal distortion has been observed to accommodate mismatch at crystal junctions and boundaries; it is proposed that such distortion arises from individual molecular distortion.