Title : Preparation of TmSe nanofilms and investigation dependence of electrophysical propertieson on the size of the characterizing particles and thickness of films
Monochalcogenids of rare earths elements (REE) are interesting materials for electronic technique, their property strongly change under the influence of the brought influences - magnetic and electrical fields, light, pressure, mechanical tension. REE compounds are interesting both in terms of practical application and from the theoretical point of the view as model objects to studying of many questions of physics and chemistry of the solid body. It especially belongs to thin films the property of which often sharply differs from properties of volume materials. To such interesting materials belongs the monoselenide of thulium (TmSe) which represents the single known system with the intermediate valency which is antiferromagneticly ordered at a low temperature. The presented work is devoted to preparation of thulium monoselenide nanofilms and studying of their electrophysical properties in dependence of the size of grains of the making films and thickness of film. Nanofilms of TmSe with 50-400 nm thicknes been grown by thermal evaporation in vacuum from two separate sources of Tm and Se on glass-ceramic, sapphire, and single-crystal silicon substrates. The substrate material has been shown to have no significant effect on the phase composition and crystallinity of the films. The optimal substrate temperature is 800–1110K. Experiments showed. that increase in temperature of a substrate increases the sizes of grains of a film so at a substrate temperature 850K diameter are equal to 15 nm and at a temperature of 1100K – 70 nm. At all temperatures of a substrate a film had structure like NaCl, at the same time with increase in temperature of a substrate lattice parameter increased from 5.49Å at 850 K to 5.65Å at 1050K. Measurements showed that with increase in the sizes of the characterizing particles the specific electroresistivity and Hall coefficient increases, the electron concentration decreases. At the room temperature is measured the dependence of a specific electroresistivity and mobility of carriers of a charge on thickness of films.