Light emission from the layered metal 2H-TaSe2 and its potential applications

Abstract

Conventional metals, in general, do not exhibit strong photoluminescence. 2H-TaSe 2 is a layered transition metal dichalcogenide that possesses metallic property with charge density wave characteristics. Here we show that 2H-TaSe 2 exhibits a surprisingly strong optical absorption and photoluminescence resulting from inter-band transitions. We use this perfect combination of electrical and optical properties in several optoelectronic applications. We show a sevenfold enhancement in the photoluminescence intensity of otherwise weakly luminescent multi-layer MoS 2 through non-radiative resonant energy transfer from TaSe 2 transition dipoles. Using a combination of scanning photocurrent and time-resolved photoluminescence measurements, we also show that the hot electrons generated by light absorption in TaSe 2 have a rather long lifetime unlike conventional metals, making TaSe 2 an excellent hot electron injector. Finally, we show a vertical TaSe 2 /MoS 2 /graphene photodetector demonstrating a responsivity of >10 AW −1 at 0.1 MHz-one of the fastest reported photodetectors using MoS 2 .

Gate- and Light-Tunable Negative Differential Resistance with High Peak Current Density in 1T-TaS2/2H-MoS2 T-Junction

“…For example, it has been recently shown that 2H-TaSe 2 , while showing excellent conductivity properties, also exhibits strong photoluminescence and long photo-carrier lifetime, allowing active metal-based device applications. 8 CDW is a macroscopic state which is exhibited by materials with reduced dimension, for example, one-dimensional and layered two-dimensional crystals. It is a result of modulation in the electronic charge arising due to a periodic modulation in the crystal lattice.…”

Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction

“…2H-TaSe 2 , which exhibits charge density wave characteristics, is metallic at room temperature with a large work function of ∼5.5 eV . TaSe 2 serves as a passive semi-transparent electrode at the top, and it can also be replaced by other transparent electrodes like ITO or graphene. Figure c,d depicts the band bending in MoS 2 under equilibrium inferred from the sign of the short circuit current ( I sc ) and open-circuit voltage ( V oc ) across the junction.…”

Influence of Dimensionality on the Charge Density Wave Phase of 2H‐TaSe2

“…The material of focus in this work is 2H-TaSe 2 , which exhibits an incommensurate (IC-) CDW phase between 122 and 90 K, as well as a commensurate CDW phase below 90 K. [31,32] This material was chosen because it has already been used in the development of Hall devices, optoelectronics, and similar applications. [33][34][35][36] Additionally, since the superconducting phase transition of 2H-TaSe 2 occurs at 0.2 K, the corresponding phase does not coexist with CDW phase, making it easier to interpret calculations and experimental data. To date, CDW formation in 1L and few-layer 2H-TaSe 2 still remains a subject of debate, warranting an elaborate investigation like the one presented here.…”