Image of a One-electron InAs Quantum Dot Inside an InAs/InP Nanowire
R. M. Westervelt (Harvard) and Lars Samuelson (Lund University)

An InAs quantum dot was formed inside an InAs/InP nanowire heterostructure by two InP barriers. The dot has the shape of a hockey puck, and it can be very small. Coulomb blockade diamonds above show that the number of electrons can be reduced to 1, then 0. Conductance through the InAs dot was imaged at liquid He temperatures by using a scanning probe microscope (SPM) tip as a moveable gate. The image above shows a Coulomb blockade ring separating 2 and 1 electrons on the dot. By changing the tip voltage the number can be reduced to 0. SPM imaging will be a powerful tool to manipulate one-electron dots inside InAs/InP nanowires.