Thus at such temperatures, transport through the dot is determined by Coulomb charging.
Smaller dots can give even higher temperatures of operation.
For an electron to tunnel onto the dot, when the applied bias is small, there must be no net energy cost of adding an electron. Thus tunnelling can only occur when the size of the dot is such that it would be neutral if it contained an integer N plus a half electrons. If the size of the dot is changed slightly, the charging energy in the two cases is no longer the same, and so the current falls to zero, only rising again when the size of the dot has changed by one electron. This effect can be seen in metal and semiconductor dots. The number of electrons in a semiconductor dot can also sometimes be reduced all the way to zero, close to which the spacing of CB peaks becomes less regular as the energy spacing of the electronic states, and the mutual Coulomb interactions of the electrons in the dot, cannot be ignored.