Low-temperature photocarrier dynamics in monolayer MoS2

TL;DR

This study investigates the temperature-dependent photocarrier dynamics in monolayer MoS2, revealing ultrafast recombination at low temperatures and complex decay behavior at higher temperatures, advancing understanding of its optoelectronic properties.

Contribution

It provides detailed time-resolved photoluminescence data on monolayer MoS2, highlighting temperature effects on carrier recombination dynamics, which was previously not well characterized.

Findings

Two distinct PL peaks emerge at low temperatures.

Photocarrier recombination occurs on the few-picosecond timescale at low temperatures.

Temperature increase leads to biexponential PL decay with a longer-lived component.

Abstract

The band structure of MoS$_2$ strongly depends on the number of layers, and a transition from indirect to direct-gap semiconductor has been observed recently for a single layer of MoS$_2$. Single-layer MoS$_2$ therefore becomes an efficient emitter of photoluminescence even at room temperature. Here, we report on scanning Raman and on temperature-dependent, as well as time-resolved photoluminescence measurements on single-layer MoS$_2$ flakes prepared by exfoliation. We observe the emergence of two distinct photoluminescence peaks at low temperatures. The photocarrier recombination at low temperatures occurs on the few-picosecond timescale, but with increasing temperatures, a biexponential photoluminescence decay with a longer-lived component is observed.