单层过渡金属二硫属化合物(TMDC),例如WSe2由于其强烈的电子-空穴相互作用而引起了越来越多的关注,被认为是开发新的光学应用的有希望的候选人。在几层政权内,这些系统对周围环境高度敏感,使得能够使用适当的衬底来调谐这些原子薄半导体的期望方面。在这种情况下,衬底提供的介电环境对这些层状材料的电子和光学性能产生重大影响,影响电子带隙和激子结合能。然而,对TMDC发光的相应影响仍在讨论中。为了阐明这些影响,我们使用了广泛的材料作为单层WSe2的衬底,从而可以在很宽的介电常数范围内观察这些影响。我们的结果表明,介电常数的增加会引起WSe2光学带隙的系统红移,这与发光强度的显着降低本质上有关。此外,我们对样品进行退火以确保WSe2和其衬底之间的紧密耦合,减少在界面中捕获的不期望的吸附物的影响。最终,我们的发现揭示了退火温度的临界程度,表明高于某个阈值,热处理会对发光产生不利影响。此外,我们的结论强调了衬底的介电特性对WSe2发光的影响,表明低介电常数有利于保持相邻单层的天然特性。
Single layers of transition metal dichalcogenides (TMDCs), such as WSe2have gathered increasing attention due to their intense electron-hole interactions, being considered promising candidates for developing novel optical applications. Within the few-layer regime, these systems become highly sensitive to the surrounding environment, enabling the possibility of using a proper substrate to tune desired aspects of these atomically-thin semiconductors. In this scenario, the dielectric environment provided by the substrates exerts significant influence on electronic and optical properties of these layered materials, affecting the electronic band-gap and the exciton binding energy. However, the corresponding effect on the luminescence of TMDCs is still under discussion. To elucidate these impacts, we used a broad set of materials as substrates for single-layers of WSe2, enabling the observation of these effects over a wide range of electrical permittivities. Our results demonstrate that an increasing permittivity induces a systematic red-shift of the optical band-gap of WSe2, intrinsically related to a considerable reduction of the luminescence intensity. Moreover, we annealed the samples to ensure a tight coupling between WSe2and its substrates, reducing the effect of undesired adsorbates trapped in the interface. Ultimately, our findings reveal how critical the annealing temperature can be, indicating that above a certain threshold, the heating treatment can induce adverse impacts on the luminescence. Furthermore, our conclusions highlight the influence the dielectric properties of the substrate have on the luminescence of WSe2, showing that a low electrical permittivity favours preserving the native properties of the adjacent monolayer.