Magnetoconductivity of Hubbard bands induced in Silicon MOSFETs
  Sodium impurities are diffused electrically to the oxide-semiconductor interface of a silicon MOSFET to create an impurity band. At low temperature and at low electron density, the band is split into an upper and a lower sections under the influence of Coulomb interactions. We used magnetoconductivity measurements to provide evidence for the existence of Hubbard bands and determine the nature of the states in each band. 
T. Ferrus, R. George, C. H. W. Barnes, N. Lumpkin, D. J. Paul and M.   Pepper