Ultraviolet light tunable single walled carbon nanotubes/n-Si junction diode

Abstract Semiconducting p-doped single walled carbon nanotubes (SWCNT) were deposited at the edge of a cleaved n-Si/SiO2 wafer. The p-n junction formed at the SWCNT/n-Si interface was tested in the presence of UV irradiation, and an immediate decrease was observed in the diode on-state current upon UV exposure. The diode ideality parameter and turn-on voltage however stayed relatively constant at 1.9 and 0.65 V respectively during the first ten minutes of UV exposure. With prolonged UV irradiation beyond 10 min these parameters increased, and the on-state current decreased by a factor of 400. We attribute this to a change in charge carriers from holes to electrons in the SWCNT’s due to UV induced photo-desorption of O2. Annealing in air at 70 °C resets the diode to its initial operating condition, thus the photo desorption process is reversible and the diode reusable. The diode was successfully tested as a signal rectifier, and its potential to sense UV radiation makes it multifunctional. It also provides a useful platform to study UV induced charge dynamics at the SWCNT/n-Si interface as carriers in the SWCNT’s switch from hole to electrons and vice versa.