Imaging the formation of a p-n junction in a suspended carbon nanotube with scanning photocurrent microscopy

TL;DR

This study employs scanning photocurrent microscopy to visualize and analyze the formation and evolution of tunable p-n junctions in suspended carbon nanotubes, revealing diode-like behavior and detailed band profile changes.

Contribution

It demonstrates in situ tunable p-n junction formation in suspended carbon nanotubes using local gates combined with SPCM and transport measurements, providing microscopic insight into junction evolution.

Findings

In situ tunable p-n and n-p junctions are created along the nanotube.

The I-V characteristics transition from resistive to rectifying behavior.

The rectification fits the Shockley diode model with a series resistor.

Abstract

We use scanning photocurrent microscopy (SPCM) to investigate individual suspended semiconducting carbon nanotube devices where the potential profile is engineered by means of local gates. In situ tunable p-n junctions can be generated at any position along the nanotube axis. Combining SPCM with transport measurements allows a detailed microscopic study of the evolution of the band profiles as a function of the gates voltage. Here we study the emergence of a p-n and a n-p junctions out of a n-type transistor channel using two local gates. In both cases the I-V curves recorded for gate configurations corresponding to the formation of the p-n or n-p junction in the SPCM measurements reveal a clear transition from resistive to rectification regimes. The rectification curves can be fitted well to the Shockley diode model with a series resistor and reveal a clear ideal diode behavior.