Negative-U properties for a quantum dot

We present the first findings of the quantum dot that exhibits the negative-U properties caused by a net attraction between the Coulombically repulsive carriers. Therefore, the finite number of electrons (or holes) inside the dot is partitioned into pairs with the second bound more strongly than the first. The negative-U properties for a quantum dot appear to result from twice the amplitude of the Coulombic oscillations with negative (or positive) variations in the sign of the gate voltage. This identification is made possible in the studies of the resonant tunnelling through the quantum dot strongly coupled to the quantum wire that is prepared by the split-gate method inside the silicon quantum well divided by the ferroelectric δ-barriers on the Si(100) surface. The negative-U double quantum dot is found to exhibit the room-temperature operation of single-hole memory such as the hysteresis in the current-voltage characteristics revealed by varying the gate voltage.