  Quantized conductance is reported in high-crystalline tin oxide (SnO2)
nanobelt back-gate field-effect transistors, at low temperatures. The quantized
conductance was observed as current oscillations in the drain current vs. gate
voltage characteristics, and were analyzed considering the nanobelt as a
quantum wire with rectangular cross-section hard-walls. The quantum confinement
in the nanowires created conditions for the successive filling of the electron
energy-subbands, as the gate voltage increases. When the source-drain voltage
is changed the oscillations are not dislocated with respect to Vg, indicating
flat-band subband energies at low temperatures. The subband separation was
found to be in good agreement with the experimental observations, since the
oscillations tend to disappear for T > 60K. Therefore, a novel quantum effect
is reported in SnO2 nanobelts, which is expected to behave as bulk at zero
electric gate fields.
