Publication Date:
2016-01-05
Description:
A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS 2 -channel-based field effect transistors. Approaches such as choosing metals with appropriate work functions and chemical doping are employed previously to improve the carrier injection from the contact electrodes to the channel and to mitigate the SBH between the MoS 2 and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS 2 . However, the physical or chemical origin of this phenomenon is not yet clearly understood. In this work, density functional theory simulations are performed, employing pseudopotentials with very high basis sets to get insights of the charge transfer between metal and monolayer MoS 2 through the inserted graphene layer. Our atomistic simulations on 16 different interfaces involving five different metals (Ti, Ag, Ru, Au, and Pt) reveal that (i) such a decrease in SBH is not consistent among various metals, rather an increase in SBH is observed in case of Au and Pt; (ii) unlike MoS 2 -metal interface, the projected dispersion of MoS 2 remains preserved in any MoS 2 -graphene-metal system with shift in the bands on the energy axis. (iii) A proper choice of metal (e.g., Ru) may exhibit ohmic nature in a graphene-inserted MoS 2 -metal contact. These understandings would provide a direction in developing high-performance transistors involving heteroatomic layers as contact electrodes.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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