Abstract
Platinum diselenide (PtSe2) is an exciting new member of the two-dimensional (2D) transition metal dichalcogenide (TMD) family. It has a semimetal to semiconductor transition when approaching monolayer thickness and has already shown significant potential for use in device applications. Notably, PtSe2 can be grown at low temperature making it potentially suitable for industrial usage. Here, we address thickness-dependent transport properties and investigate electrical contacts to PtSe2, a crucial and universal element of TMD-based electronic devices. PtSe2 films have been synthesized at various thicknesses and structured to allow contact engineering and the accurate extraction of electrical properties. Contact resistivity and sheet resistance extracted from transmission line method (TLM) measurements are compared for different contact metals and different PtSe2 film thicknesses. Furthermore, the transition from semimetal to semiconductor in PtSe2 has been indirectly verified by electrical characterization in field-effect devices. Finally, the influence of edge contacts at the metal–PtSe2 interface has been studied by nanostructuring the contact area using electron beam lithography. By increasing the edge contact length, the contact resistivity was improved by up to 70% compared to devices with conventional top contacts. The results presented here represent crucial steps toward realizing high-performance nanoelectronic devices based on group-10 TMDs.
Highlights
Over the last decade, the need for further miniaturization and increased functionality of electronic devices has triggered massive research in two-dimensional (2D) channel materials such as graphene and transition metal dichalcogenides (TMDs).[1,2,3] Reliable electrical contacts between devices/materials and metal electrodes are crucial, as the contact resistance can strongly influence or dominate the behavior of the entire device
As reported in our previous studies,[32,33] the PtSe2 synthesized by a thermally assisted conversion (TAC) process has a polycrystalline structure, which is observed in scanning electron microscopy (SEM) images (Fig. S1 of the Supplementary Information) of the PtSe2 film surface
According to atomic-force microscopy (AFM) measurements of the thicknesses of Pt layers before and after selenization, it has been found that the initial Pt thickness expands approximately four times after selenization
Summary
The need for further miniaturization and increased functionality of electronic devices has triggered massive research in two-dimensional (2D) channel materials such as graphene and transition metal dichalcogenides (TMDs).[1,2,3] Reliable electrical contacts between devices/materials and metal electrodes are crucial, as the contact resistance can strongly influence or dominate the behavior of the entire device. Electron beam lithography (EBL) was used to fabricate transmission line method (TLM) structures to extract contact resistivity and sheet resistance of the PtSe2 devices. PtSe2 device channels were synthesized by direct selenization of pre-deposited Pt layers with different thicknesses.
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