Transition between quantum Hall conductor and Hall insulator in Si MOSFET’s

We measured the conductor-insulator transition in a two-dimensional electron system in a Si metal-oxide-semiconductor field-effect transistor with low peak electron mobility ${\mathrm{\mu }}_{\mathrm{peak}}$=0.91 ${\mathrm{m}}^2$/V s and compared the results with those observed in a sample with ${\mathrm{\mu }}_{\mathrm{peak}}$=2.71 ${\mathrm{m}}^2$/V s. The behavior of ${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$ and ${\mathrm{\sigma }}_{\mathit{x}\mathit{y}}$ at Landau-level filling factor ν=2 depends on a dimensionless parameter ${\mathrm{\omega }}_{\mathit{c}}$τ in both samples. Here, ${\mathrm{\omega }}_{\mathit{c}}$ is the cyclotron frequency and τ is the relaxation time of an electron determined in the absence of magnetic field. Oscillations of phase boundaries in ν≳1 regions in the ${\mathit{N}}_{\mathit{s}}$-B plane are similar to each other. These observations show that the transition is caused by Anderson localization due to disorder, not by a formation of an electron solid.