Energy schematic for charge transfer via conduction band (black arrow) and via surface states, E_t, (blue arrow) upon applying a negative potential V_a to the n-type semiconductor. Note that both the band bending, eV_bb, and the HHL drop, ΔE_HH, have decreased because the original CPD is smaller by eV_a. The relative potential drop between semiconductor and HHL has been assumed to be of similar size.