Single layer CVD MoS2 for flexible electronics

Hugo Casademont (1) , Yu-Pu Lin (1) , Renaud Cornut (1) , Bruno Jousselme (1) , Vincent Derycke (1)

1 LICSEN - Laboratoire Innovation en Chimie des Surfaces et NanoSciences

Two dimensional layered semiconductors, and in particular transition metal dichalcogenides such as molybdenum disulfide (MoS 2), have recently received increasing attention due to the combination of their unique electronic properties with their atomically thin geometry. In particular, single-layer MoS 2 possesses key properties that make it especially appealing as channel material in flexible field-effect transistors: a sizable band-gap, mechanical robustness, absence of dangling bonds / chemical stability, appropriate electron mobility, compatibility with room-temperature transfer and device fabrication process-flows. Among the numerous issues that need to be solved, two are of particular importance: (1) MoS 2 must be grown at a large-scale and at low-cost while achieving crystalline quality comparable to exfoliated layers from natural crystals, (2) MoS 2 should be associated with other flexible elements within the FETs notably high-quality flexible insulators as gate dielectrics. At the GDRI-GNT conference, we would like to present our recent contributions to these questions. We synthesized single-layer MoS 2 by CVD and optimized the conditions to grow either large-size individual triangular domains (up to 100µm large) or fully-covering domains (cm 2 scale). Extensive characterizations allowed assessing the material quality. We then integrated this material in rigid and flexible FETs. In parallel we studied a new class of gate dielectrics based on electro-grafted organic thin films. These robust covalent organic dielectrics are produced at room temperature and under mild conditions. The process yields uniform films of adjustable thickness (in the 4-50 nm range depending on the molecular compounds and grafting parameters). We first build transistors combining exfoliated MoS 2 as channel material with one example of such new dielectrics on rigid substrates [1]. The transistors operate at low bias (gate swing of 1.5V and V DS =0.5V), exhibit steep subthreshold slope as low as 110 mV/decade and are hysteresis-free due to the hydrophobic and trap-free nature of this dielectric. Very recently, we showed, using a different organic compound, that this approach can be combined with single-layer CVD MoS 2 and integrated on flexible substrates [2].

Domains: Material chemistry

Hugo Casademont, Yu-Pu Lin, Renaud Cornut, Bruno Jousselme, Vincent Derycke. Single layer CVD MoS2 for flexible electronics. Annual Meeting of the GDR-I Graphene Nanotubes, Oct 2016, Saint Pierre d'Oléron, France. ⟨cea-02351407⟩