Investigation of and Raman Modes of Few-Layer MoS₂ on HfO₂ Substrate

Hui-chun Chien

Recently the research work by Radisavljevic et al.[1] shows that the mobilities of monolayer MoS₂ transistors can be improved by employing a thin layer of hafnium oxide as  top-gate dielectric. Dielectric screening has been successfully demonstrated to suppress the Coulomb interactions of charged impurities on the substrate. Therefore, we develop an alternative method of building a monolayer MoS₂ transistor on HfO₂ substrate. Owing to the low contrast of few-layer MoS₂ flakes on thin HfO₂ substrate, which makes the realization of such device configuration difficult. By utilizing the thickness dependence of  in-plane and out-of-plane Raman modes of MoS₂ flakes, and, respectively, we establish an efficient approach to improve the identification of MoS₂ layers by Raman spectrum instead of AFM. Our investigation of and Raman modes of few-layer MoS₂ on HfO₂ substrate shows the significant difference from those on SiO₂ substrate. The substrate effect of Raman spectrum as well as its further application will be discussed in this talk.

Reference:  [1]. Radisavljevic, et al., Nat. Nanotech. 6, 147 (2011)