Ionic Gate Spectroscopy of 2D Semiconductors

Abstract

Reliable and precise measurements of the relative energy of band edges in semiconductors are needed to determine band gaps and band offsets, as well as to establish the band diagram of devices and heterostructures. These measurements are particularly important in the field of two-dimensional materials, in which many new semiconducting systems are becoming available through exfoliation of bulk crystals. For two-dimensional semiconductors, however, commonly employed techniques suffer from difficulties rooted either in the physics of these systems, or of technical nature. The very large exciton binding energy, for instance, prevents the band gap to be determined from a simple spectral analysis of photoluminescence, and the limited lateral size of atomically thin crystals makes the use of conventional scanning tunneling spectroscopy cumbersome. Ionic gate spectroscopy is a newly developed technique that exploits ionic gate field-effect transistors to determine quantitatively the relative alignment of band edges of two-dimensional semiconductors in a straightforward way, directly from transport measurements (i.e., from the transistor electrical characteristics). The technique relies on the extremely large geometrical capacitance of ionic gated devices that -- under suitable conditions -- enables a change in gate voltage to be directly related to a shift in chemical potential. Here we present an overview of ionic gate spectroscopy, and illustrate its relevance with applications to different two-dimensional semiconducting transition metal dichalcogenides and van der Waals heterostructures.

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Cited by in corpus (11)

• Generating extreme electric fields in 2D materials by dual ionic gating
• Quenching the band gap of 2D semiconductors with a perpendicular electric field
• Control of proton transport and hydrogenation in double-gated graphene
• Full control of solid-state electrolytes for electrostatic gating
• The impact of valley profile on the mobility and Kerr rotation of transition metal dichalcogenides
• Observation of the anomalous Hall effect in a layered polar semiconductor
• Light sources with bias tunable spectrum based on van der Waals interface transistors
• Topological bands in the PdSe${}_2$ pentagonal monolayer
• Mechanism of the electrochemical hydrogenation of graphene
• Unexpected large electrostatic gating by pyroelectric charge accumulation
• Universal low-density power laws of the dc conductivity and Hall constant in the self-consistent Born approximation