Tuning Transition-Metal Dichalcogenide Field-Effect Transistors by Spontaneous Pattern Formation of an Ultrathin Molecular Dopant Film.

Abstract

Spontaneous pattern formation is an energetically favorable process and is shown in nature in molecular-scale assembly, biological association, and soft material organizations. The opposite regime, the artificial process, which is widely applied to the fabrication of semiconducting devices, such as lithographic techniques, requires enormous amounts of energy. Here, we propose a concept of tuning the properties of semiconducting MoS₂ and WSe₂ devices using the spontaneous pattern formation of adjacent molecular films. The film used was a 10 nm thick ultrathin film of a molecular electron dopant, which exhibited spontaneous pattern formation and dynamically transformed the morphology of tiny holes, a network, a maze, and dots on substrates, including SiO₂, MoS₂, and WSe₂. These patterns were exhibited only when the film came in contact with water and was tuned with temperature and time. The specific lengths of the patterns were less than 200 nm, which is sufficiently smaller than the exfoliated ∼10 μm semiconducting MoS₂ and WSe₂ flakes. The properties of the field-effect devices of MoS₂ and WSe₂ were found to be modified according to the pattern formation process of the ultrathin molecular film on the device. This concept applies the spontaneous patterning phenomena shown in nature to the fabrication and optimization of electronic devices by using molecular films and their responses to the external environment.