Electron-Doping-Enhanced Trion Formation in Monolayer Molybdenum Disulfide Functionalized with Cesium Carbonate

Abstract

We report effective and stable electron doping of monolayer molybdenum disulfide (MoS2) by cesium carbonate (Cs2CO3) surface functionalization. The electron charge carrier concentration in exfoliated monolayer MoS2 can be increased by about 9 times after Cs2CO3 functionalization. The n-type doping effect was evaluated by in situ transport measurements of MoS2 field-effect transistors (FETs) and further corroborated by in situ ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering measurements. The electron doping enhances the formation of negative trions (i.e., a quasiparticle comprising two electrons and one hole) in monolayer MoS2 under light irradiation and significantly reduces the charge recombination of photoexcited electron-hole pairs. This results in large photoluminescence suppression and an obvious photocurrent enhancement in monolayer MoS2 FETs.

Surface transfer doping induced effective modulation on ambipolar characteristics of few-layer black phosphorus

“…Chemical doping, as a simple and effective doping approach, has been widely utilized to manipulate the electronic properties of 2D materials as well as organic semiconductors 13,[32][33][34][35][36] . Compared with the electrostatic modulation via an external electrical field, chemical doping usually provides a stronger nonvolatile doping capability with the ease of device fabrication 37 .…”

“…Surface transfer doping relies on the interfacial charge transfer without introducing significant defects into the lattice structure of the as-doped materials, thereby nearly reserving their fundamental transport properties 38 . Various organic and inorganic species have demonstrated excellent doping effects on 2D materials such as graphene and TMDs, among which caesium carbonate (Cs 2 CO 3 ) and molybdenum trioxide (MoO 3 ) have been used to effectively modify the doping level of MoS 2 and grapheme, respectively 32,33 . Furthermore, the contact doping on TMDs FETs, such as MoS 2 and WSe 2 , has been shown to remarkably enhance the device performance owing to the effective modulation of Schottky barrier formed at contact/ semiconductor interface 13,36 .…”

Valley Polarized Single Photon Source Based on Transition Metal Dichalcogenides Quantum Dots

“…The strong spin-orbit interaction in the valence band gives rise to a separation between them, as shown in Figure 9. In addition, an injection of electrons into the conduction band of MoS 2 , which can be realized by gate-doping [26], photoionization of impurities [28], substrates [25] or functionalization layers [22,27], leads to the formation of negatively charged excitons ðX À Þ. The peak of the X À is positioned at a lower energy side of neutral exciton with a binding energy about 36 meV for MoS 2 , see the peak indicated by X À in Figure 10.…”

“…In addition, it should be kept in mind that the presence of defects is not always beneficial for the PL signal. For instance, defect-mediated nonradiative recombination might result in an internal quantum yield droop in the defective TMDCs [26][27][28]. In this context, single quantum emitter based on QD is desirable [14,15].…”

Photoluminescence Enhancement in Monolayer Molybdenum Disulfide by Annealing in Air

“…而最近的研究表明, 电子 可以被激子束缚形成负电激子, 从而改变二硫化钼荧光 光谱的特点 [10] . 二硫化钼的电子分布可以通过栅极电 [14,15] . 气体分子吸附导致荧光光谱 的强烈变化为 TMDCs 在气体探测甚至是生物传感上的 应用打开了一扇大门.…”