(Invited) Excellent Wetting Behavior of Yttria on 2D Materials

A high quality yttrium oxide (yttria, Y₂O₃) dielectric has been grown on different carbon derivatives materials (carbon nanotubes, exfoliated graphene, chemical vapor deposition graphene).^1-5 This opens the possibility to use such dielectric for the fabrication of graphene devices.^4-5 In this talk, the good wettability of Y₂O₃ on graphene is demonstrated using various surface science methods. Furthermore, the favorable wetting behavior of yttria is exploited as an effective seeding layer for atomic layer deposition of Al₂O₃ on graphene.⁶ Moreover, we investigated the interface between Y₂O₃ and the transition metal dichalcogenide MoS₂ as well as on highly ordered pyrolytic graphite (HOPG). The growth of the yttria film was monitored in-situ by monochromatic X-ray photoelectron spectroscopy and scanning tunneling microscopy (XPS and STM). Depositing yttrium metal results in a chemical interaction between the adlayer and the substrate. However, no indication of chemical interaction was detected for the Y₂O₃ growth, formed by evaporating yttrium in background O₂ environment. This is due to the initial formation of Y-O bonds, before the weak Y-MoS₂ and Y-C interaction occurs. The STM results indicate the formation of a uniform dielectric film on both MoS₂ and HOPG surfaces, confirming the previous findings on graphene. In conclusions, our results reveal that the underlying MoS₂and graphene remains intact following yttria seed deposition. Photoemission measurements of the graphene/oxide contacts indicate n-type doping of graphene with different doping levels caused by the charge transfer at the interfaces.

This work was supported in part by the Southwest Academy on Nanoelectronics sponsored by the Nanoelectronic Research Initiative.

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