Insulator-to-metal phase transition in a few-layered MoSe2 field effect transistor

Nihar R Pradhan; Carlos Garcia; Bhaswar Chakrabarti; Daniel Rosenmann; Ralu Divan; Anirudha V Sumant; Suzanne Miller; David Hilton; Denis Karaiskaj; Stephen A McGill

doi:10.1039/d2nr05019f

Insulator-to-metal phase transition in a few-layered MoSe₂ field effect transistor

Nanoscale. 2023 Feb 9;15(6):2667-2673. doi: 10.1039/d2nr05019f.

Authors

Nihar R Pradhan^{1

2}, Carlos Garcia^{2

3}, Bhaswar Chakrabarti^{4

5}, Daniel Rosenmann⁴, Ralu Divan⁴, Anirudha V Sumant⁴, Suzanne Miller⁴, David Hilton⁶, Denis Karaiskaj⁷, Stephen A McGill²

Affiliations

¹ Layered Materials and Device Physics Laboratory, Department of Chemistry, Physics and Atmospheric Science, Jackson State University, Jackson, MS 39217, USA. nihar.r.pradhan@jsums.edu.
² National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, FL 32310, USA. mcgill@magnet.fsu.edu.
³ Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USA.
⁴ Center for Nanoscale Materials, Argonne National Laboratory, 9700 S-Cass Avenue, Lemont, IL-60439, USA.
⁵ Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu-600036, India.
⁶ Department of Physics, Baylor University, One Bear Place 97316, Waco, TX 76798-7316, USA.
⁷ Department of Physics, University of South Florida, Tampa, FL 33620, USA.

PMID: 36652441
DOI: 10.1039/d2nr05019f

Abstract

The metal-to-insulator phase transition (MIT) in low-dimensional materials and particularly two-dimensional layered semiconductors is exciting to explore due to the fact that it challenges the prediction that a two-dimensional system must be insulating at low temperatures. Thus, the exploration of MITs in 2D layered semiconductors expands the understanding of the underlying physics. Here we report the MIT of a few-layered MoSe₂ field effect transistor under a gate bias (electric field) applied perpendicular to the MoSe₂ layers. With low applied gate voltage, the conductivity as a function of temperature from 150 K to 4 K shows typical semiconducting to insulating character. Above a critical applied gate voltage, V_c, the conductivity becomes metallic (i.e., the conductivity increases continuously as a function of decreasing temperature). Evidence of a metallic state was observed using an applied gate voltage or, equivalently, increasing the density of charge carriers within the 2D channel. We analyzed the nature of the phase transition using percolation theory, where conductivity scales with the density of charge carriers as σ ∝ (n - n_c)^δ. The critical exponent for a percolative phase transition, δ(T), has values ranging from 1.34 (at T = 150 K) to 2 (T = 20 K), which is close to the theoretical value of 1.33 for percolation to occur. Thus we conclude that the MIT in few-layered MoSe₂ is driven by charge carrier percolation. Furthermore, the conductivity does not scale with temperature, which is a hallmark of a quantum critical phase transition.