Ultrafast Laser Spectroscopy of Two‐Dimensional Materials Beyond Graphene

Abstract

Starting with the discovery of graphene in 2004, the interest in two-dimensional materials since then has been exponentially growing. Across many disciplines, their exceptional electrical, chemical, thermal, and optical properties have drawn considerable attention that has created an entire field within a decade of their discovery. Driven by the mechanical exfoliation technique that allows for the quick exploration of these two-dimensional materials and their novel devices, joint efforts have been made in order to understand and exploit their potential, consequently leading to the development of their large-scale growth. This review focuses on recent studies using ultrafast laser spectroscopy that have revealed the photocarrier dynamics in two-dimensional materials and laid the foundation of their behavior. We provide a brief introduction on ultrafast laser spectroscopy, discuss several aspects of the photocarrier dynamics, and conclude with our perspective on future developments.

Optical Properties and Photocarrier Dynamics of Bi2O2Se Monolayer and Nanoplates

“…Hence, we conclude that the recombination lifetime of the photocarriers in Bi 2 O 2 Se nanoplates is about 200 ps. This lifetime is longer than that of 2D TMDs …”

“…Photocarrier dynamics was studied by a homemade transient absorption setup with high spatial and temporal resolution . An 820 nm and 100 fs pulse from a 80 MHz Ti:sapphire oscillator was divided into two parts by a beamsplitter.…”

“…Transient Absorption: Photocarrier dynamics was studied by a homemade transient absorption setup with high spatial and temporal resolution. [32] An 820 nm and 100 fs pulse from a 80 MHz Ti:sapphire oscillator was divided into two parts by a beamsplitter. One part pumped an optical parametric oscillator to generate a visible output, serving as the probe pulse.…”

“…This lifetime is longer than that of 2D TMDs. [32] To study the transport properties of photocarriers in Bi 2 O 2 Se nanoplates, we performed spatially and temporally resolved pump-probe measurements with pump and probe laser spot sizes of about 2 µm. The probe spot was scanned across the pump spot by tilting a mirror in the probe arm and thus changing the incident angle of the probe to the objective lens.…”

Ultrafast Carrier Dynamics and Bandgap Renormalization in Layered PtSe2

“…Understanding ultrafast dynamical processes in 2D materials is essential for exploring many‐body phenomena and light–matter coupling from a fundamental physics point of view. Many interesting effects, such as excitonic quasiparticle interactions, hot carrier transport, Mott transition, valley selective optical Stark effect, bandgap renormalization, and charge density waves, can be probed with ultrafast carrier dynamics . Moreover, it is possible to engineer the material's response through carrier injection by ultrafast laser pulses .…”