Tungsten Disulfide Nanodispersions for Inkjet Printing and Semiconducting Devices
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Tungsten Disulfide Nanodispersions for Inkjet Printing and Semiconducting Devices Jay A. Desai1, Nirmal Adhikari2, Anupama B. Kaul2 1 Department of Metallurgical, Materials and Biomedical Engineering 2 Department of Electrical and Computer Engineering University of Texas at El Paso, El Paso, TX 79968, USA. ABSTRACT In this work, we demonstrate optical and electrical transport properties of chemically exfoliated WS2 in cyclohexanone/ terpineol solvent using different sonication times. High electrical conductivity of WS2 nanodispersions was observed when appropriate amount of voltage was applied indicating their semi-conductive behavior. Surface morphology of WS2 nanodispersions sonicated at different times were studied using optical microscopy. Optical bandgap of WS2 nanodispersions were determined from optical absorbance spectrum. Inkjet printing was used to demonstrate uniform distribution of WS2 nanosheets and their precise and large scale printability. These dispersions indicate the potential of WS2 in various optoelectronic and semiconducting device applications.
INTRODUCTION Two-dimensional (2-D) materials or atomically thin materials have been subject of great research interest since the discovery of first 2-D material, graphene, in 2004 by Geim and Novosolov [1] which exhibited high strength, high electrical and thermal conductivity and other remarkable properties like complete impermeability, stretchability and transparency [2]. Inspired by graphene, many researchers [3-5] investigated other layered materials like transition metal dichalcogenides and hexagonal boron nitride (h-BN), whose atomic structure is similar to graphene. These materials allows for the creation and production of variety of structures and properties when they are reduced to their 2-D forms from their bulk three-dimenional (3-D) counterparts. Molybdenum and tungsten dichalcogenides in their monolayer forms are direct band-gap semiconductors and they have a sizeable bandgap of 1-2 eV in the visible regime. Given that they exist naturally in the earth’s crust and are abundantly available it makes them useful for future applications in diverse areas [6]. Liquid-phase exfoliation is the most widely used approaches for exfoliating individual monolayers from bulk materials [7, 8]. Inkjet printing of these exfoliated 2-D materials can then be used as material-saving deposition technique to print various patterns with the ability define relatively precise areas and geometries [9, 10] on various substrate. The present work demonstrates simple but effective route to produce 2-D nanosheets of WS2 by sonication-assisted exfoliation of bulk WS2 layered powder in cyclohexanone/terpineol solution using different sonication times. Optical and electrical response of annealed spin-coated and inkjet printed WS2 nanodispersions has also been demonstrated to compare the effectiveness of both techniques.
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