Abstract
Scalable heterojunctions based on two-dimensional transitional metal dichalcogenides are of great importance for their applications in the next generation of electronic and optoelectronic devices. However, reliable techniques for the fabrication of such heterojunctions are still at its infancy. Here we demonstrate a simple technique for the scalable fabrication of lateral heterojunctions via selective chemical doping of TMD thin films. We demonstrate that the resistance of large area MoS2 and MoSe2 thin film, prepared via low pressure chalcogenation of molybdenum film, decreases by up to two orders of magnitude upon doping using benzyl viologen (BV) molecule. X-ray photoelectron spectroscopy (XPS) measurements confirms n-doping of the films by BV molecules. Since thin films of MoS2 and MoSe2 are typically more resistive than their exfoliated and co-evaporation based CVD counterparts, the decrease in resistance by BV doping represents a significant step in the utilization of these samples in electronic devices. Using selective BV doping, we simultaneously fabricated many lateral heterojunctions in 1 cm2 MoS2 and 1 cm2 MoSe2 films. The electrical transport measurements performed across the heterojunctions exhibit current rectification behavior due to a band offset created between the doped and undoped regions of the material. Almost 84% of the fabricated devices showed rectification behavior demonstrating the scalability of this technique.
Highlights
Scalable heterojunctions based on two-dimensional transitional metal dichalcogenides are of great importance for their applications in the generation of electronic and optoelectronic devices
We demonstrated a simple technique for the doping of transition metal dichalcogendies (TMDs) thin films and used selective doping for scalable fabrication of lateral heterojunctions
We show for the first time that when MoS2 and MoSe2 thin films, grown via low pressure sulfurization and selenization of Mo films, are immersed into benzyl viologen (BV) solution, the resistance decreases by up to two-orders of magnitude due to the surface charge transfer based doping
Summary
Scalable heterojunctions based on two-dimensional transitional metal dichalcogenides are of great importance for their applications in the generation of electronic and optoelectronic devices. We demonstrate a simple technique for the scalable fabrication of lateral heterojunctions via selective chemical doping of TMD thin films. The stacking of 2D layered materials by mechanical exfoliation is a widely used method to create van der Waals heterostructures for laboratory research In this process the mechanically exfoliated thin layer of one TMD is transferred to another type of TMD by using intermediate polymer to form a heterojunction[14,19,36,37]. While large area TMD thin films, prepared via chalcogenization of metal (molybdenum, tungsten) or metal oxide films[44,45], could be useful in the fabrication of heterojunctions, development of reliable techniques for scalable fabrication is still at its infancy. One useful technique could be the selective chemical doping of 2D TMD thin films for the fabrication of lateral heterojunctions. Doping of 2D TMD thin films by using BV molecules could change their charge carriers and transport properties and selective doping could open up the possibility of creating a band offset with undoped TMD thin films to fabricate many TMD based heterojunctions in a massively parallel fashion
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