Mobility improvement and temperature dependence in MoSe 2 field-effect transistors on parylene-C substrate

Bhim Chamlagain, Qing Li, Nirmal Jeevi Ghimire, Hsun Jen Chuang, Meeghage Madusanka Perera, Honggen Tu, Yong Xu, Minghu Pan, Di Xaio, Jiaqiang Yan, David Mandrus, Zhixian Zhou

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Abstract

We report low-temperature scanning tunneling microscopy characterization of MoSe 2 crystals and the fabrication and electrical characterization of MoSe 2 field-effect transistors on both SiO 2 and parylene-C substrates. We find that the multilayer MoSe 2 devices on parylene-C show a room-temperature mobility close to the mobility of bulk MoSe 2 (100-160 cm 2 V -1 s -1 ), which is significantly higher than that on SiO 2 substrates (≈50 cm 2 V -1 s -1 ). The room-temperature mobility on both types of substrates are nearly thickness-independent. Our variable-temperature transport measurements reveal a metal-insulator transition at a characteristic conductivity of e 2 /h. The mobility of MoSe 2 devices extracted from the metallic region on both SiO 2 and parylene-C increases up to ≈500 cm 2 V -1 s -1 as the temperature decreases to ≈100 K, with the mobility of MoSe 2 on SiO 2 increasing more rapidly. In spite of the notable variation of charged impurities as indicated by the strongly sample-dependent low-temperature mobility, the mobility of all MoSe 2 devices on SiO 2 converges above 200 K, indicating that the high temperature (>200 K) mobility in these devices is nearly independent of the charged impurities. Our atomic force microscopy study of SiO 2 and parylene-C substrates further rules out the surface roughness scattering as a major cause of the substrate-dependent mobility. We attribute the observed substrate dependence of MoSe 2 mobility primarily to the surface polar optical phonon scattering originating from the SiO 2 substrate, which is nearly absent in MoSe 2 devices on parylene-C substrate.

Original languageEnglish
Pages (from-to)5079-5088
Number of pages10
JournalACS Nano
Volume8
Issue number5
DOIs
StatePublished - May 27 2014

Keywords

  • field-effect transistor
  • mobility
  • surface phonon scattering

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