Fabrication of heterojunctions and current-voltage characteristics of vanadium coordination compounds

Current voltage (I-V) characteristics of the films of four vanadium complexes, VO2(3-fl) (1) (3-fl = 3-Hydroxyflavone), VO(pbd)(2) (pbd = 1-Phenyl-1,3-butadione) (2), VO(dbm)(2) (dbm = Dibenzoylmethane) (3), and VO(acac)(2) (acac = Acetylacetonate) (4), have been investigated at room temperature. The films were grown on copper (Cu) and Aluminum (AI) substrates by using a centrifugal machine operated at 183, 733 and 1650 g values. I-V characteristics of all samples showed non-linear rectification behavior. All complexes exhibited higher conductivity for Cu than Al substrate indicating that Cu and V complex contact resistance is lower than that of Al. Press tablets of the samples exhibited p-type semiconductor behavior. In 1 and 4, a switching effect from low conductance to high conductance states was observed. An abrupt increase in the current at threshold voltage may be related to switching effect from low to high conductivity state, At relatively low current the switching effect was reversible for both substrates, whereas at high current it was only reversible for Al. Heterojuction samples of Cu/1/TiO2/Ga and Al/4/TiO2/Ga (TiO2 = titanium oxide) were also fabricated and they were found to be p-n aniso type.