Room temperature observation of quantum confinement in single InAs nanowires

Quantized conductance in nanowires can be observed at low temperature in transport measurements; however, the observation of sub-bands at room temperature is challenging due to temperature broadening. So far, conduction band splitting at room temperature has not been observed in III-V nanowires mainly due to the small energetic separations between the sub-bands. We report on the measurement of conduction sub-bands at room temperature, in single InAs nanowires, using Kelvin probe force microscopy. This method does not rely on charge transport but rather on measurement of the nanowire Fermi level position as carriers are injected into a single nanowire transistor. As there is no charge transport, electron scattering is no longer an issue, allowing the observation of the sub-bands at room temperature. We measure the energy of the sub-bands in nanowires with two different diameters, and obtain excellent agreement with theoretical calculations based on an empirical tight-binding model.