INFLUENCE OF STRAIN ON THE ELECTRONIC-PROPERTIES OF EPITAXIAL V2O3 THIN-FILMS

Thin films of V2O3 with thickness of 20-450 nm were grown on (0001) or iented sapphire substrates by reactive electron-beam evaporation. Low- energy electron diffraction, X-ray diffraction and atomic force micros copy studies show highly oriented grains with a lateral size of 50 to 800 nm, dependent on substrate temperature and deposition rate. The fi lms were characterized by transmission measurements in the optical and infrared region, electrical resistance and Hall effect measurements. A variation of the growth parameters yields three different ''types'' of V2O3 films characterized by (i) a metal-insulator transition simila r to bulk material (type 1), (ii) an insulator-metal followed by a met al-insulator transition (type 2) below room temperature and (iii) an i nsulator-insulator transition (type 3). The different types of V2O3 fi lms mimic the behavior of chromium doped V2O3 with increasing Cr conce ntration. The c lattice parameter correlates with the electronic prope rties of the respective films, suggesting that this effect might be ex plained by a varying degree of strain in the films. (C) 1997 Elsevier Science S.A.