As the size of electronic structures continues to decrease, the classical view of electron motion transforms into a fully quantum picture based on interacting electron states and wavefunctions. To understand this quantum picture, we need to visualize where electrons are and understand how they move. A liquid-He cooled scanning probe microscope (SPM) is used to extract both the energy and the wavefuction of individual electron states inside a semiconductor nanostructure, using Coulomb blockade spectroscopy. The sample is a long, thin InAs quantum dot in an InAs/InP nanowire, which contains a row of electrons that form a one-dimensional electron gas. The wavefunction can be imaged by locally denting the wavefunction with the SPM tip, which acts as a moveable gate, and recording the resulting change in energy of the quantum state as the tip is moved along the dot. The group plans to investigate the predicted transition from a Wigner crystal to a Luttinger liquid as the number of electrons is increased. Research and education will be integrated through the training of graduate students, and through summer research experiences for undergraduate students.
As the size of electronic devices decreases, quantum mechanics becomes increasingly important. Our classical view of electron motion transforms into a quantum picture based on interacting electron states and wavefunctions. A technique is being developed to measure the energy of individual electron states and map their wavefunctions using a cooled scanning probe microscope (SPM). A row of electrons is held inside a long quantum dot formed in an InAs/InP nanowire - the nanowire is so narrow that the electrons must line up, one after the other. The energy of a single electron state is measured using Coulomb blockade spectroscopy - current can flow through the dot only when the energy required to add or remove an electron drops to zero. The wavefunction is mapped by denting the wavefunction with the charged SPM tip, and measuring the change in energy of the quantum state as the tip is moved along the dot. In this way, the SPM can visualize the quantum picture in order to develop new types of quantum devices from nanostructures. Research and education will be integrated through the training of graduate students, and through summer research experiences for undergraduate students.