Extrinsic and Intrinsic Photoresponse in Monodisperse Carbon Nanotube Thin Film Transistors

TL;DR

This paper uses advanced microscopy to differentiate intrinsic and extrinsic photoresponses in monodisperse SWCNT thin film transistors, revealing how substrate and nanotube excitation contribute to photocurrent behavior.

Contribution

It introduces spectroscopic, time-resolved scanning photocurrent microscopy to distinguish intrinsic nanotube responses from substrate effects in SWCNT transistors.

Findings

Persistent positive photocurrent from near-IR excitation due to free carriers in SWCNTs.

Transient positive displacement current from shorter wavelength excitation.

Persistent negative photocurrent from photogating effects in the SWCNT film.

Abstract

Spectroscopic, time-resolved scanning photocurrent microscopy is shown to distinguish the intrinsic photoresponse of monodisperse semiconducting (99%) single-walled carbon nanotubes (SWCNTs) from the extrinsic photoresponse of the substrate. A persistent positive photocurrent induced by near-IR excitation is attributed to the generation of free carriers by inter-band excitation in SWCNTs. For shorter excitation wavelengths, absorption by the Si substrate generates two types of photocurrent: a transient positive photoresponse, identified as a displacement current, and a persistent negative photocurrent that arises from photogating of the SWCNT thin film.