Fabrication of back-gated Transition Metal Dichalcogenides (TMD) flake-based field-effect-transistor (FET) devices


Typical process flow
Mechanical exfoliation with scotch tape is used to obtain thin flakes from a TMD bulk crystal (e.g. MoS2, WS2). The flakes are transferred on a substrate of 85nm of dry thermally grown SiO2 and a highly doped Si handle wafer to facilitate back-gating. The height of the flakes is established by optical color-contrast and by Atomic Force Microscopy (AFM). Metal contact pads and electrodes are defined by electron beam lithography, followed by metal evaporation and a lift off process. An adhesion layer of 5nm of Ti and 45nm of Au are deposited with e-beam evaporation. Scanning Electron Microscopy (SEM) is then used for inspection to confirm good overlap between the flake and the metal contact pads, without breakages or discontinuities.

Ascent+ facility

Platform Technologies

  • Nano for Quantum Technologies
  • Disruptive Devices

Key Enabling Capability

  • Processing
  • Devices / Test structures

Mirabelli G., Schmidt M., Sheehan B., Cherkaoui K., Monaghan S., Povey I., McCarthy M., Bell A.P., Nagle R., Crupi F., Hurley P.K., Duffy R., “Back-gated Nb-doped MoS2 junctionless field-effect-transistors”, (2016) AIP Advances, 6 (2), art. no. 025323 [DOI: 10.1063/1.4943080]

Mirabelli G., Gity F., Monaghan S., Hurley P.K., Duffy R., “Impact of impurities, interface traps and contacts on MoS2 MOSFETs: Modelling and experiments”, (2017) European Solid-State Device Research Conference, art. no. 8066648, pp. 288 – 291 [DOI: 10.1109/ESSDERC.2017.8066648]

Key Enabling Capability

Devices / Test Structures, Processing

Platform Technology

Disruptive Devices, Nano for Quantum Technologies