Sharp metal-insulator transition in Sr(Ti1−xVx)O3−δ thin films on SrTiO3 substrates

We fabricated Sr(Ti1−xVx)O3 composition-spread films on SrTiO3 (100) substrates by using pulsed laser deposition in ultra high vacuum. Sharp metal-insulator (MI) transitions were observed in the case of Sr(Ti1−xVx)O3−δ composition-spread films grown on an oxygen deficient SrTiO3 (STO) buffer/SrTiO3 (STO) substrate in the restricted composition x=0.5-1.0 while no MI transition was observed in the case of Sr(Ti1−xVx)O3−δ below x=0.5. In the insulating phase below the MI transition, non-linear I-V characteristics were observed. To explain the appearance and disappearance of MI transitions in Sr(Ti1−xVx)O3−δ two possibilities were considered: (i) strain effect from the substrate and (ii) charge-transfer at the interface between Sr(Ti1−xVx)O3−δ and STO.