Strong Photothermoelectric Response and Contact Reactivity of the Dirac Semimetal ZrTe5

TL;DR

This study investigates the photothermoelectric response of ZrTe5 Dirac semimetal devices, revealing high sensitivity and significant reactivity issues that impact device performance and understanding of photocurrent mechanisms.

Contribution

It provides the first spatially-resolved photocurrent analysis of ZrTe5 nanoplatelets, highlighting the importance of reactivity and thermoelectric effects in device behavior.

Findings

Achieved noise-equivalent power as low as 42 pW/Hz^{1/2} at room temperature.

Identified significant surface reactivity and contact reactions affecting device stability.

Demonstrated the influence of reactivity on photocurrent mechanisms.

Abstract

The family of three-dimensional topological insulators opens new avenues to discover novel photophysics and to develop novel types of photodetectors. ZrTe5 has been shown to be a Dirac semimetal possessing unique topological electronic and optical properties. Here we present spatially-resolved photocurrent measurements on devices made of nanoplatelets of ZrTe5, demonstrating the photothermoelectric origin of the photoresponse. Due to the high electrical conductivity and good Seebeck coefficient, we obtain noise-equivalent powers as low as 42 pW/Hz1/2 at room temperature for visible light illumination at zero bias. We also show that these devices suffer from significant ambient reactivity such as the formation of a Te-rich surface region driven by Zr oxidation, as well as severe reactions with the metal contacts. This reactivity results in significant stresses in the devices, leading to unusual geometries that are useful for gaining insight into the photocurrent mechanisms. Our results indicate that both the large photothermoelectric response and reactivity must be considered when designing or interpreting photocurrent measurements in these systems.