Novel features of quantum Hall plateaus for varying interface charge

A systematic study of quantum Hall plateaus has been made in Si metal-oxide-semiconductor field-effect transistors having driftable ${\mathrm{Na}}^{+}$ ions. For low interface ion densities ($N_{\mathrm{ox}}\lesssim 2\times {10}^{11}$ ${\mathrm{cm}}^{-2\mathrm{}}$) the positions of plateaus for filled spin and valley levels exhibit unexpected shifts with respect to those for completely filled Landau levels, and the widths of plateaus for filled Landau levels increase more rapidly with interface charge than do those for filled spin and valley levels. These results have interesting implications for features of the density of states of the system and for aspects of interface electron scattering.