Absence of a Band Gap at Interface of a Metal and Highly Doped Monolayer $Mo{S}_2$

Abstract

High quality electrical contact to semiconducting transition metal dichalcogenides (TMDCs) such as $Mo{S}_2$ is key to unlocking their unique electronic and optoelectronic properties for fundamental research and device applications. Despite extensive experimental and theoretical efforts reliable ohmic contact to doped TMDCs remains elusive and would benefit from a better understanding of the underlying physics of the metal-TMDC interface. Here we present measurements of the atomic-scale energy band diagram of junctions between various metals and heavily doped monolayer $Mo{S}_2$ using ultra-high vacuum scanning tunneling microscopy (UHV-STM). Our measurements reveal that the electronic properties of these junctions are dominated by 2D metal induced gap states (MIGS). These MIGS are characterized by a spatially growing measured gap in the local density of states (L-DOS) of the $Mo{S}_2$ within 2 nm of the metal-semiconductor interface. Their decay lengths extend from a minimum of ~0.55 nm near mid gap to as long as 2 nm near the band edges and are nearly identical for Au, Pd and graphite contacts, indicating that it is a universal property of the monolayer semiconductor. Our findings indicate that even in heavily doped semiconductors, the presence of MIGS sets the ultimate limit for electrical contact.

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Cited by in corpus (8)

• Magnetism in Semiconducting Molybdenum Dichalcogenides
• Contact resistance and interfacial engineering: Advances in high-performance 2D-TMD based devices
• GW band structure of monolayer MoS2 using the SternheimerGW method and effect of dielectric environment
• Magnetic proximity effect at the interface of two-dimensional materials and magnetic oxide insulators
• Twist angle dependent electronic properties of exfoliated single layer MoS${}_2$ on Au(111)
• Charge density waves and Fermi level pinning in monolayer and bilayer SnSe${}_2$
• Gap states and valley-spin filtering in transition metal dichalcogenide monolayers
• Improving Electric Contacts to Two-Dimensional Semiconductors