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Electrically controlled dielectric band gap engineering in a two-dimensional semiconductor
摘要： The emergent class of atomically thin two-dimensional (2D) materials has opened up completely new opportunities for manipulating electronic quantum states at the nanoscale. Here we explore the concept of dielectric band gap engineering, i.e., the controlled manipulation of the band gap of a semiconductor via its dielectric environment. Using first-principles calculations based on the GW self-energy approximation we show that the band gap of a two-dimensional (2D) semiconductor, such as the transition metal dichalcogenides, can be tuned over several hundreds of meV by varying the doping concentration in a nearby graphene sheet. Importantly, these significant band gap renormalizations are achieved via nonlocal Coulomb interactions and do not affect the structural or electronic integrity of the 2D semiconductor. We investigate various heterostructure designs, and show that, depending on the size of the intrinsic dielectric function of the 2D semiconductor, the band gap can be tuned by up to 1 eV for graphene carrier concentrations reachable by electrostatic doping. Our work provides opportunities for electrically controllable band gap engineering in 2D semiconductors.
关键词： GW self-energy approximation,transition metal dichalcogenides,graphene,two-dimensional semiconductor,dielectric band gap engineering
更新于2025-09-23 15:19:57
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Excitonic effects on layer- and strain-dependent optoelectronic properties of PbI2
摘要： Exciton states have obvious effects on optical properties of two-dimensional (2D) materials. Here, we investigate excitonic effects on electronic and optical properties of PbI2 by using GW + Bethe-Salpeter equation method, considering the layer number and strain effect. These studies show that exciton states obviously modify and dominate the optical absorption of 2D PbI2 nanosheets. Also, with the increasing number of layers, the intensity of main absorption peak increases and the exciton binding energy decreases. Meanwhile, the tensile strain can induce the threshold energy of optical spectra shift down the low energy, and exciton binding energy has a maximum at the strain of 3%. Therefore, our results indicate that the 2D PbI2 nanomaterials have excellent ultraviolet absorption and corresponding potential for the application of optoelectronic devices.
关键词： Optical property,Electronic structure,Lead iodide,Excitonic effects,Two-dimensional semiconductor
更新于2025-09-09 09:28:46