Damage-free mica/MoS₂ interface for high-performance multilayer MoS₂ field-effect transistors

Abstract

For top-gated MoS 2 field-effect transistors, damaging the MoS 2 surface to the MoS 2 channel are inevitable due to chemical bonding and/or high-energy metal atoms during the vacuum deposition of gate dielectric, thus leading to degradations of field-effect mobility (μ FE ) and subthreshold swing (SS). A top-gated MoS 2 transistor is fabricated by directly transferring a 9 nm mica flake (as gate dielectric) onto the MoS 2 surface without any chemical bonding, and exhibits excellent electrical properties with an on-off ratio of ∼10 8 , a low threshold voltage of ∼0.2 V, a record μ FE of 134 cm 2 V −1 s −1 , a small SS of 72 mV dec −1 and a low interface-state density of 8.8×10 11 cm −2 eV −1 , without relying on electrode-contact engineered and/or phase-engineered MoS 2 . Although the equivalent oxide thickness of the mica dielectric is in the sub-5 nm regime, enhanced stability characterized by normalized threshold voltage shift (1.2×10 −2 V MV −1 cm −1 ) has also been demonstrated for the transistor after a gate-bias stressing at 4.4 MV cm −1 for 10 3 s. All these improvements should be ascribed to a damage-free MoS 2 channel achieved by a dry transfer of gate dielectric and a clean and smooth surface of the mica flake, which greatly decreases the charged-impurity and interface-roughness scatterings. The proposed transistor with low threshold voltage and high stability is highly desirable for lowpower electronic applications.

Insulators for 2D nanoelectronics: the gap to bridge

“…Mica is another interesting layered 2D insulator that has been investigated as a back-gate insulator in GFETs 126 and top-gate insulator in MoS 2 FETs 133 . In addition to having a well-defined surface, this 2D insulator has a reasonably high permittivity (8.1) and a wide bandgap (10.5 eV), which would address some of the limitations of hBN.…”

2D semiconductors for specific electronic applications: from device to system

“…The disadvantage of such in situ oxides is that they are only effective for specific oxidable 2D semiconductors, instead limiting the choice of 2D semiconductors. Figure 5e summarizes the performance of different dielectrics as a top-gate dielectric on 2D materials including a comparison with silicon processes 73,[75][76][77] . Some data points indicate that the high-κ dielectric integrated on 2D materials are already comparable to industrial requirements.…”

Recent advances in low‐dimensional semiconductor nanomaterials and their applications in high‐performance photodetectors

“…TMDs, belonging to semiconductors, have the widely adjustable bandgap and electrical properties, which is widely used in the field of electronics. For example, MoS 2 has a relative high carrier mobility, large on/off ratio (~10 8 ), and lower subthreshold swing (SS) value. Moreover, as the number of layers decreases, MoS 2 undergoes a transition from an indirect bandgap to a direct bandgap (single layer), and a significant increase in luminous efficiency occurs in the single layer MoS 2 .…”