Abstract
Two-dimensional transition metal dichalcogenides (2D-TMDs) are among the most promising materials for exploring and exploiting exciton transitions. Excitons in 2D-TMDs present remarkably long lifetimes, even at room temperature. The spectral response of exciton transitions in 2D-TMDs has been thoroughly characterized over the past decade by means of photoluminescence spectroscopy, transmittance spectroscopy, and related techniques; however, the spectral dependence of their electronic response is still not fully characterized. In this work, we investigate the electronic response of exciton transitions in monolayer MoSe2 via low-temperature photocurrent spectroscopy. We identify the spectral features associated with the main exciton and trion transitions, with spectral bandwidths down to 15 meV. We also investigate the effect of the Fermi level on the position and intensity of excitonic spectral features, observing a very strong modulation of the photocurrent, which even undergoes a change in sign when the Fermi level crosses the charge neutrality point. Our results demonstrate the unexploited potential of low-temperature photocurrent spectroscopy for studying excitons in low-dimensional materials, and provide new insight into excitonic transitions in 1L-MoSe2.
Highlights
Two-dimensional transition metal dichalcogenides (2D-TMDs) are an ideal material platform for exciton physics
Our results demonstrate the unexploited potential of low-temperature photocurrent spectroscopy for studying excitons in low-dimensional materials, and provide new insight into excitonic transitions in Citation: Vaquero, D.; Salvador-Sánchez, J.; Clericò, V.; Diez, Keywords: excitons; transition metal dichalcogenides; photocurrent spectroscopy
As we demonstrated in a recent publication [8], low-temperature photocurrent spectroscopy (PCS) [9,10,11] provides another simple, powerful, and yet largely underused complementary approach for studying excitonic transitions in 2D-TMDs
Summary
Two-dimensional transition metal dichalcogenides (2D-TMDs) are an ideal material platform for exciton physics. This family of materials presents unusually large exciton binding energies and lifetimes, even at room temperature; their optical and optoelectronic properties are largely dominated by excitonic transitions [1]. Excitonic devices based on 2D-TMDs often rely on the so-called bright exciton states, i.e., exciton states that are capable of emitting light upon relaxation. These exciton states are typically studied and characterized via photoluminescence spectroscopy and related techniques. In recent years, different characterization techniques—such as absorption spectroscopy [2,3,4,5,6] or electroluminescence spectroscopy [7]—have increasingly gained popularity due to their potential for investigating excitonic states not accessible via PL
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