Nanotube electronic states observed with thermal field emission electron spectroscopy

Abstract

We observe nonmetallic electronic states above the Fermi level in single-walled carbon nanotubes by measuring the energy distribution of thermal-field-emitted electrons. This measurement method examines electronic states associated with the nanotube cap or end termination, and with it, we resolve electronic states greater than 3 eV above the Fermi level. The observed emitting states are broad at high temperatures (0.7–1.5 eV full width at half maximum), and the peak positions shift linearly with applied voltage. We present possible mechanisms responsible for these states.