Spectroscopic comprehension of Mott-Hubbard insulator to negative charge transfer metal transition in LaNixV1−xO3 thin films

The room temperature (300 K) electronic structure of pulsed laser deposited\nLaNi_{x}V_{1-x}O_{3} thin films have been demonstrated. The substitution of\nearly-transition metal (TM) V in LaVO_{3} thin films with late-TM Ni leads to\nthe decreasing in out-of-plane lattice parameter. Doping of Ni does not alter\nthe formal valence state of Ni and V in LaNi_{x}V_{1-x}O_{3} thin films,\ndivulging the absence of carrier doping into the system. The valence band\nspectrum is observed to comprise of incoherent structure owing to the localized\nV 3d band along with the coherent structure at Fermi level. With increase in Ni\nconcentration, the weight of the coherent feature increases, which divulges its\norigin to the Ni 3d-O 2p hybridized band. The shift of Ni 3d-O 2p hybridized\nband towards higher energy in Ni doped LaVO_{3} films compared to the LaNiO_{3}\nfilm endorses the modification in ligand to metal charge transfer (CT) energy.\nThe Ni doping in Mott-Hubbard insulator LaVO_{3} leads to the closure of\nMott-Hubbard gap by building of spectral weight that provides the delocalized\nelectrons for conduction. A transition from bandwidth control Mott-Hubbard\ninsulator LaVO_{3} to negative CT metallicity character in LaNiO_{3} film is\nobserved. The study reveals that unlike in Mott-Hubbard insulators where the\nstrong Coulomb interaction between the 3d electrons decides the electronic\nstructure of the system, CT energy can deliver an additional degree of freedom\nto optimize material properties in Ni doped LaVO_{3} films.\n