Abstract
Metal contacts play a fundamental role in nanoscale devices. In this work, Schottky metal contacts in monolayer molybdenum disulfide (MoS2) field-effect transistors are investigated under electron beam irradiation. It is shown that the exposure of Ti/Au source/drain electrodes to an electron beam reduces the contact resistance and improves the transistor performance. The electron beam conditioning of contacts is permanent, while the irradiation of the channel can produce transient effects. It is demonstrated that irradiation lowers the Schottky barrier at the contacts because of thermally induced atom diffusion and interfacial reactions. The simulation of electron paths in the device reveals that most of the beam energy is absorbed in the metal contacts. The study demonstrates that electron beam irradiation can be effectively used for contact improvement through local annealing.
Highlights
Molybdenum disulfide (MoS2) is one of the most studied transition metal dichalcogenides, owing to its layered structure and useful mechanical, chemical, electronic, and optoelectronic properties.[1−4] A molybdenum (Mo) atomic plane sandwiched between two sulfur (S) planes constitutes the monolayer that is bonded to other monolayers by weak van der Waals forces to form the bulk material. several applications,[5−9]
We investigated the effects of 10 keV electron beam irradiation of the Schottky metal contacts in MoS2-based field-effect transistors (FETs)
The electrical measurements revealed that electron beam irradiation improves the device conductance, reduces the rectification of the output characteristic, and causes a left shift of the threshold voltage
Summary
Molybdenum disulfide (MoS2) is one of the most studied transition metal dichalcogenides, owing to its layered structure and useful mechanical, chemical, electronic, and optoelectronic properties.[1−4] A molybdenum (Mo) atomic plane sandwiched between two sulfur (S) planes constitutes the monolayer that is bonded to other monolayers by weak van der Waals forces to form the bulk material. several applications,[5−9]. We present the spectroscopic and electrical characterization of monolayer MoS2-based FETs, with Schottky Ti/Au contacts, focusing on the effects of low-energy e-beam irradiation. The local heat can induce atomic diffusion and interfacial reactions that change the chemical composition and structure of the metal−MoS2 interface or can generate or release tensile strain Both effects cause the lowering of the Schottky barrier and the consequent increase in transistor current. The chosen reference measurements are spectra obtained from MoS2 flakes on the same substrate, which were in contact with the photoresist and various solvents during the processing and lift-off for the production of the FETs, but are not in contact with metal electrodes themselves. The e-beam of SEM, set to 10 keV and 10 pA, was used for the time-controlled irradiation of specific parts of the device
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