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Summary:Common and different aspects of scanning electron microscope (SEM) and scanning ion microscope (SIM) images are discussed from a viewpoint of interaction between ion or electron beams and specimens. The SIM images [mostly using 30 keV Ga focused ion beam (FIB)] are sensitive to the sample surface as well as to low-voltage SEM images. Reasons for the SIM images as follows: (1) no backscatteredelectron excitation; (2) low yields of backscattered ions; and (3) short ion ranges of 20-40nm, being of the same order of escape depth of secondary electrons (SE) [=(3-5) times the SE mean free path]. Beam charging, channeling, contamination, and surface sputtering are also commented upon.

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The absorption spectra and quantum yields of various heterocyclic fulgides were measured. The absorption maxima of the colored photocyclization products of fulgides were dependant upon the structure of heterocyclic rings and the substituent; and increase of the electron-donating ability of the heterocyclic ring caused a red shift of λmax. A quantum yield measurement of the photochromic reaction of fulgides revealed that not only the steric effect, but also the electronic effect of substituent (e.g. p-(dimethylamino)phenyl, cyano, acetyl) introduced into the heterocycles, changed the reactivity for both coloration and bleaching.

Aiming at practical uses of photochromic compounds as data-storage media, electron-donating (e.g. p-dimethylaminophenyl) and conjugate chain (e.g. p-dimethylaminostyryl) substituted heterocyclic fulgides, e.g. 2-[1-(2-substituted 5-methyl-4-oxazolyl)ethylidene]-3-isopropylidenesuccinic anhydride and 2-[1-(5-substituted 2-methyl-3-thienyl)ethylidene or methlyene]-3-isopropylidenesuccinic anhydride, were prepared. The effect on photochromic performance was also investigated; it was clarified that substituents had effects on the red-shift and a significant increase in the color intensity of a colored form. However, the rate of the discoloration reaction was also affected, depressed, by the substituent.