Structural stability and electronic transitions of NdNi0.98Zn0.02O3−δ thin films

NdNiO3 is a multiband system and shows temperature-driven first-order metal to insulator phase transition. Divalent Zn doping at trivalent Ni-site in NdNiO3 injects holes in the system. To study the effects of oxygen variation in a combination of Zn doping, NdNi1−xZnxO3−δ (x = 0, 0.02) thin films (30 nm) have been deposited on single-crystal LaAlO3 (001) substrate. The broadening of temperature-driven metal–insulator transition reduces drastically just by 2% Zn-doping at Ni-site. Further, the variation in oxygen content in NdNi0.98Zn0.02O3−δ films modifies the structural and electronic properties quite systematically and significantly. The Raman modes related to Ni–O bonds get blue-shifted due to the increase in oxygen content of thin films. A comparative study of the films with and without doping clearly shows that Zn-doping provides stability to the structure for the single-phase formation despite oxygen deficiency. The oxygen-deficient insulating films show activation behaviour at high temperatures, indicating an opening of charge-transfer gap.