In-plane gate single electron transistor fabricated by AFM lithography

Coulomb blockade is observed in semiconductor quantum dots fabricated by sc anning probe lithography. We demonstrate that by combining top gates with i n-plane gates, the lithographic shape of a dot can be transferred into the electron gas with high accuracy. Furthermore, by applying voltages to the i n-plane gates, the number of electrons on the dot can be changed by more th an 70 without changing its shape. Transport measurements in high magnetic f ields and with positive top gate voltages applied indicate that the potenti al walls of the nanostructure can be made very steep.