Abstract
The failure to achieve stable Ohmic contacts in two-dimensional material devices currently limits their promised performance and integration. Here we demonstrate that a phase transformation in a region of a layered semiconductor, PdSe2, can form a contiguous metallic Pd17Se15 phase, leading to the formation of seamless Ohmic contacts for field-effect transistors. This phase transition is driven by defects created by exposure to an argon plasma. Cross-sectional scanning transmission electron microscopy is combined with theoretical calculations to elucidate how plasma-induced Se vacancies mediate the phase transformation. The resulting Pd17Se15 phase is stable and shares the same native chemical bonds with the original PdSe2 phase, thereby forming an atomically sharp Pd17Se15/PdSe2 interface. These Pd17Se15 contacts exhibit a low contact resistance of ∼0.75 kω μm and Schottky barrier height of ∼3.3 meV, enabling nearly a 20-fold increase of carrier mobility in PdSe2 transistors compared to that of traditional Ti/Au contacts. This finding opens new possibilities in the development of better electrical contacts for practical applications of 2D materials.
| Original language | English |
|---|---|
| Pages (from-to) | 8928-8936 |
| Number of pages | 9 |
| Journal | Journal of the American Chemical Society |
| Volume | 141 |
| Issue number | 22 |
| DOIs | |
| State | Published - Jun 5 2019 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The device fabrication and characterization were conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. A.O. acknowledges fellowship support from the UT/ORNL Bredesen Center for Interdisciplinary Research and Graduate Education. A.H. and D.M. acknowledge support from the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant No. GBMF4416. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility. Theoretical work by T.L.F. and S.T.P. is supported in part by the Department of Energy Grant DE-FG0209ER46554 and by the McMinn Endowment. Computations at Vanderbilt University and ORNL were performed at NERSC funded through Contract No. DE-AC02-05CH11231. Computations also used the Extreme Science and Engineering Discovery Environment (XSEDE) resources. The electron microscopy (S.Z.Y. and M.F.C.) was supported in part by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and through a user proposal supported by ORNL’s Center for Nanophase Materials Sciences, which is sponsored by the Scientific User Facilities Division of the U.S. Department of Energy.