[en] Electron energy loss spectroscopy (EELS) and electron microscopy were conducted on the polymorphism of vacuum-deposited titanium dioxide films on a potassium chloride substrate. As-deposited amorphous films were crystallized to rutile and anatase modifications of titanium dioxide by intense electron beam irradiation. By EELS, tungsten from the evaporation source was found in all of the prepared films. Potassium and chlorine were also found in rutile and antase crystals, respectively. The appearance of the anatase crystals was attributed to incorporation of the chlorine impurities. (author)