| AVS 62nd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Wednesday Sessions |
| Session 2D+EM+IS+MC+NS+SP+SS-WeA |
| Session: | Dopants and Defects in 2D Materials |
| Presenter: | Christopher Smyth, University of Texas at Dallas |
| Authors: | C.M. Smyth, University of Texas at Dallas S. McDonnell, University of Texas at Dallas R. Addou, University of Texas at Dallas H. Zhu, University of Texas at Dallas C.L. Hinkle, University of Texas at Dallas R.M. Wallace, University of Texas at Dallas |
| Correspondent: | Click to Email |
Transition metal dichalcogenides (TMDs) have been studied for years due to their tribological properties, but recent discoveries have illuminated unique opportunities for the use of single or few layer TMDs in electronics, specifically tunnel field effect transistors (TFETs). The properties of FETs fabricated with single and few layer TMDs have been investigated with some degree of success, but it has been shown via in-situ chemical analysis that interface interactions between certain contact metals and the underlying TMD are not fully understood1,2.
In this study, the wettability and reactivity of various metals with a number of bulk TMDs (MoS2, HfSe2, SnSe2, etc.) were investigated. Multiple samples were processed in parallel to ensure that all sample sets saw identical metal depositions. The metal-TMD interface was monitored in-situ using X-ray photoelectron spectroscopy (XPS) and metal film topography was imaged using atomic force microscopy (AFM). For some low work function metals, noticeable differences in interface chemistry were found between samples that saw high vacuum rather than UHV metal e-beam depositions.
Significant variations in compatibility between contact metal and TMD were discovered. These variations were dependent upon the metal-TMD pair and the base pressure of the chamber prior to metal deposition. Au exhibits far superior wettability on MoSe2, where uniform thin films were achieved, compared to ReSe2, on which Au grows as clusters. Au wettability varies between that of thin films and clusters for the other TMDs studied. An Au thin film deposited on SnSe2 results in the formation of reaction products such as Sn metal, as evidenced by the evolution of different chemical states in the Sn 3d spectrum after deposition. Reactions between MoS2 and Sc producing Mo metal occur when Sc is deposited in UHV instead of HV. These results provide further understanding for the critical interface between Sc and TMD in high performance TFETs.
This work was supported in part by NSF Award No. 1407765, the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, and by the Southwest Academy on Nanoelectronics (SWAN) sponsored by the Nanoelectronic Research Initiative and NIST.
[1] McDonnell, S.; Addou, R.; Buie, C.; Wallace, R. M.; Hinkle, C. L. Defect Dominated Doping and Contact Resistance in MoS2. ACS Nano 2014, 8, 2880-2888.
[2] Das, S.; Chen, H.Y.; Penumatcha, A. V.; Appenzeller, J. High Performance Multi-Layer MoS2 Transistors with Scandium Contacts. Nano Lett. 2012, 12, 100-105.