This proposal was received in response to the Spin Electronics for the 21st century Initiative Program Solicitation NSF 02-036. The proposal focuses on fabrication and characterization of two prototype carbon nanotube spin electronic devices: the nanotube spin transistor and the nano-helix magnetic field sensor. For molecular scale spin electronic applications, the carbon nanotube has compelling advantages. Carbon nanotubes are quasi-one-dimensional, crystalline wires having a low density of spin scattering centers. Therefore, current flows through nanotubes with very few electron or spin scattering events. This makes carbon nanotubes useful for molecular scale spin transmission lines, with spin detection signals remaining high over long transmission distances. Spin signals can be amplified or suppressed by gating the nanotube to change the electron density. High ballistic current flow also produces anomalously large magnetic moments in carbon nanotube circuits. This is useful for magnetic memory and switching applications to amplify and sense local magnetic fields.
The nanotube spin transistor is a ferromagnetically contacted nanotube with a field effect gate. The gate bias modifies the transmission of the up and down spin channels, and acts to amplify or suppress the spin detection signal. The nano-helix magnetic sensor is an electrically contacted carbon nanotube grown into a helical shape. Due to the lack of electron scattering, current flow through the helix produces a giant orbital spin moment, which interacts strongly with applied magnetic field. This dramatically alters the resistance between the two field directions, even for low applied fields. Together, these devices display a range of behavior that will be useful for advanced spin electronic applications on the molecular scale. To accomplish this work, the PIs will combine their collective experience in carbon nanotube spin transport, nanotube device fabrication, nanotube electrical characterization and nanotube device modeling. They will work closely with collaborators within the chemistry departments at Duke University and UC Riverside to optimize nanotube growth, distribution of nanotubes for electrical characterization, and chemical surface modification of nanotubes for spin electronic device applications. As part of their project, they will be training two graduate students in the exciting area of spin electronics and nanoscale technology. The undergraduate and graduate curriculum including Nanoscale fabrication, Device Modeling, and Electrical/ Optical Characterization will incorporate their spin electronic research advances.
