We report on a systematic study of the temperature-dependent Hall coefficient and thermoelectric power in ultra-thin metallic LaNiO3 films that reveal a strain-induced, self-doping carrier transition that is inaccessible in the bulk. As the film strain varies from compressive to tensile at fixed composition and stoichiometry, the transport coefficients evolve in a manner strikingly similar to those of bulk hole-doped superconducting cuprates with varying doping level. Density functional calculations reveal that the strain-induced changes in the transport properties are due to self-doping in the low-energy electronic band structure. The results imply that thin-film epitaxy can serve as a new means to achieve hole-doping in other (negative) charge-transfer gap transition metal oxides without resorting to chemical substitution.
@article{arxiv.1204.2039,
title = {Strain-controlled band engineering and self-doping in ultrathin LaNiO$_3$ films},
author = {E. J. Moon and J. M. Rondinelli and N. Prasai and B. A. Gray and M. Kareev and J. Chakhalian and J. L. Cohn},
journal= {arXiv preprint arXiv:1204.2039},
year = {2012}
}