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Project Topic
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This project will integrate 2D materials with newly developed free-standing nanolayers of organic semiconductors to create van der Waals heterostructures for applications in electronic and optoelec-tronic systems. Progress in nanotechnology has led to an enormous interest in two-dimensional (2D) materials, hav-ing a huge market potential in electronics. In addition to exploiting the novel properties of individual 2D crystals, van der Waals heterostructures (vdWh) comprising several different materials hold promise for novel devices with designed properties. Here we propose a new approach to integrate nanolayers (5-10 nm) of organic semiconductors (OSC) with inorganic 2D materials, which could contribute significantly to technological advancement by exploiting the properties of both materials. For practical application of vdWh, large scale preparation of heterostructures without compromising their crystallinity and interface quality is required. So far, the primary challenges lie in the difficulty of preparation of high quality, ordered and uniform ul-trathin OSC layers on top of 2D crystals over a large area. To address these challenges, this project will utilize novel methods to fabricate vdWh with 2D mate-rials while retaining their structural integrity and high interface quality. We will develop 5-10 nm of OSC that are mechanically stable and transferable by crosslinking and layer transfer methods. Specif-ically, we will produce p–n junctions of OSC and atomically thin CVD grown transition metal di-chalcogenides (TMDCs), in a lateral and vertical configuration for demonstration of devices such as diodes and transistors. Our fabrication methods provide a broad choice of OSC materials with p and n-type carriers ( we will start with pentacene, DNTT and epindolidione) that will allow us to investigate both type I and type II heterojunctions with 2D TMDC materials (MoS2, WSe2). The p-n junctions will be integrated with other 2D materials to form all-2D vdWhs with improved device characteristics. CVD graphene will be used as contact materials to OSC and TMDC, where the band alignment and interface resistance can be controlled with gate voltage by tuning the Schottky barrier. Furthermore, we will integrate the recently developed carbon nanomembranes (CNM) as dielectrics in the vdWh devices. We will utilize our cutting-edge expertise in growth, nanofabrication, spectroscopy, optical and elec-trical transport methods to understand the vdWh heterointerfaces and to develop novel electronic and optoelectronic devices. For basic understanding of vdWhs we plan to use our experience in (syn-chrotron based) photoemission spectroscopy for characterization of electronic structure, electrical transport measurements for understanding the charge transport properties, optical characterization by photocurrent spectroscopy measurements. These proposed vdWh electronic and optoelectronic devices will allow us to exploit the advantages offered by both 2D materials and OSC: Excellent elec-trical and optical properties, flexibility, large area and low-cost production, atomically flat interfaces, excellent gate control over the junction and a great potential for scalability.
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