MoS<inf>2</inf>/VO<inf>2</inf> vdW heterojunction devices: Tunable rectifiers, photodiodes and field effect transistors

Abstract

In this work we report a new class of ultra-thin film devices based on n-n van der Waals (vdW) heterojunctions of MoS2 and VO2, which show remarkable tunable characteristics. The favorable band alignment combined with the sharp and clean vdW interface determines a tunable diode-like characteristic with a rectification ratio larger than 10 3. Moreover, the heterojunction can be turned into a Schottky rectifier with higher on-current by triggering the VO2 insulator to metal transition (IMT), by either applying a sufficiently large voltage or increasing the temperature above 68 °C. The proposed devices are photosensitive with linear photoresponse and temperature tunable photoresponsivity values larger than 1 in the 500/650 nm wavelength range. We finally report the first ever field-effect transistor based on gated MoS2/VO2 heterojunctions, which is a true low power FET exploiting a phase change material where the electrostatic doping effect of the gate on the junction results in a subthreshold slope (SS) of 130 mV/dec at room temperature, ION/IOFF > 10 3 and IOFF < 5 pA/μm at VD=1.5V. I.

Gate-Tunable Thermal Metal–Insulator Transition in VO2 Monolithically Integrated into a WSe2 Field-Effect Transistor

“…The positive bias current increases greatly with temperature because the insulator-to-metal transition in VO 2 is thermally induced. Similar diode-like behavior has been observed in the van der Waals heterostructure of n-type multilayer MoS 2 and VO 2 , , where the rectification results from the barrier formed between the conduction band edge of MoS 2 and the Fermi level of VO 2 . However, because WSe 2 can be both n- and p-types, in contrast to MoS 2 , the observed rectification behavior could be explained not only by the VO 2 /WSe 2 junction but also by the WSe 2 /Ti Schottky junction, the contribution of which varies with the carrier type of WSe 2 .…”

“…If WSe 2 is n-type, the rectifying current most likely results from the barrier formed between the Fermi level of VO 2 and the conduction band edge of WSe 2 , similar to the previously reported VO 2 /MoS 2 junction. 22,23 However, the barrier formed at the VO 2 /WSe 2 junction is expected to be larger than that at the VO 2 /MoS 2 junction because WSe 2 has a lower electron affinity than MoS 2 . 24 Alternatively, if WSe 2 is ptype, the WSe 2 /Ti Schottky contact plays a role in the rectification behavior.…”

WSe2/SnSe2 vdW heterojunction Tunnel FET with subthermionic characteristic and MOSFET co-integrated on same WSe2 flake

“…WSe 2 flakes have been mechanically exfoliated directly on the patterned substrate starting from commercially available bulk samples. In order to form the junction, SnSe 2 flakes were first exfoliated on a poly(dimethylsiloxane) (PDMS) transparent substrate and then deterministically transferred on previously selected WSe 2 samples 32,33 . The source and drain contacts were deposited by lift-off of a Cr/Pd stack (5/50 nm) after a second EBL step on MMA/PMMA bilayer resist.…”

Phase Transition-Induced Temperature-Dependent Phonon Shifts in Molybdenum Disulfide Monolayers Interfaced with a Vanadium Dioxide Film

“…The recent progress in atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDs) beyond graphene has led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, energy conversion, opto-electronics, and spintronics because of solution processability and a unique combination of van der Waals interactions, tunable bandgaps, strong spin–orbit coupling, and favorable electronic/mechanical properties. − Furthermore, combining functional 2D TMD materials into heterostructures through hybrid integration with other materials, such as Si, GaN, , SiC, organic materials, and oxides, − has recently attracted increasing attention for exploring new physics and providing desirable multiple functionalities.…”