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

摘要

For top-gated MoS2 field-effect transistors, damaging the MoS2 surface to the MoS2 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 (mu(FE)) and subthreshold swing (SS). A top-gated MoS2 transistor is fabricated by directly transferring a 9 nm mica flake (as gate dielectric) onto the MoS2 surface without any chemical bonding, and exhibits excellent electrical properties with an on-off ratio of similar to 10(8), a low threshold voltage of similar to 0.2 V, a record mu(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 x 10(11) cm(-2) eV(-1), without relying on electrode-contact engineered and/or phase-engineered MoS2. 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 x 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 MoS2 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 low-power electronic applications.