EFFECTS OF QUANTUM LEVELS ON TRANSPORT THROUGH A COULOMB ISLAND

Transport measurements are used to study the quantized energy levels i n a small electron gas, referred to as a Coulomb island. First, large- bias measurements reveal the excitation spectrum of the island. Second , small-bias measurements probe the intrinsic line shape of energy lev els. Line shapes are generally fit well by thermally broadened Lorentz ians. In addition, a decrease in the charging energy of the island is observed as the coupling to its leads is increased. This effect is sho wn to be consistent with a dramatic increase in one of the island-lead capacitances.