Identifying signatures of photothermal current in a double-gated semiconducting nanotube

TL;DR

This study uses scanning photocurrent microscopy on double-gated semiconducting nanotubes to distinguish photovoltaic and photothermal effects, revealing how doping and contact resistance influence photocurrent generation mechanisms.

Contribution

It provides new insights into the mechanisms of photocurrent in SWNTs, emphasizing the roles of doping profiles and contact resistance, which is crucial for optoelectronic device development.

Findings

Photothermal and photovoltaic effects both contribute to photocurrent.

Doping profile determines the dominant photocurrent mechanism.

Series resistance influences the magnitude of photocurrent contributions.

Abstract

The remarkable electrical and optical properties or single-walled carbon nanotubes (SWNT) allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here, we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting SWNT and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from SWNTs.