title: Pressure-Modulated Conductivity, Carrier Density, and Mobility of Multilayered Tungsten Disulfide.
abstract: Tungsten disulfide (WS2) is a layered transition metal dichalcogenide (TMD) that differs from other two-dimensional (2D) compounds such as graphene due to its unique semiconducting, tunable-band-gap nature. Multilayered WS2 exhibits an indirect band gap Eg of ∼1.3 eV, along with a higher load-bearing ability that is promising for strain-tuning device applications, but the electronic properties of multilayered WS2 at higher strain conditions (i.e., static strain >12%) remain an open question. Here we have studied the structural, electronic, electrical, and vibrational properties of multilayered WS2 at hydrostatic pressures up to ∼35 GPa experimentally in a diamond anvil cell and theoretically using first-principles ab initio calculations. Our results show that WS2 undergoes an isostructural semiconductor-to-metallic (S-M) transition at approximately 22 GPa at 280 K, which arises from the overlap of the highest valence and lowest conduction bands. The S-M transition is caused by increased sulfur-sulfur interactions as the interlayer spacing decreases with applied hydrostatic pressure. The metalization in WS2 can be alternatively interpreted as a 2D to 3D (three-dimensional) phase transition that is associated with a substantial modulation of the charge carrier characteristics including a 6-order decrease in resistivity, a 2-order decrease in mobility, and a 4-order increase in carrier concentration. These distinct pressure-tunable characteristics of the dimensionalized WS2 differentiate it from other TMD compounds such as MoS2 and promise future developments in strain-modulated advanced devices.
authors.forename: Avinash P
authors.initials: AP
authors.lastname: Nayak
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Collaborative Innovation Center of Quantum Matt , Beijing 100190, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Department of Civil and Environmental Engineering, Computational Materials Science Group, George Washington University , 20052, Washington, D.C., United States.
authors.forename: Boxiao
authors.initials: B
authors.lastname: Cao
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Center for High Pressure Science and Advanced Technology Research (HPSTAR) , Shanghai 201900, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Wu
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Moran
authors.affiliation: Department of Civil and Environmental Engineering, Computational Materials Science Group, George Washington University , 20052, Washington, D.C., United States.
authors.forename: Tianshu
authors.initials: T
authors.lastname: Li
authors.forename: Deji
authors.initials: D
authors.lastname: Akinwande
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Collaborative Innovation Center of Quantum Matt , Beijing 100190, China.
authors.forename: Changqing
authors.initials: C
authors.lastname: Jin
authors.affiliation: Center for High Pressure Science and Advanced Technology Research (HPSTAR) , Shanghai 201900, China.
authors.forename: Jung-Fu
authors.initials: JF
authors.lastname: Lin
keywords: 2D materials; diamond anvil cell; pressure engineering; strain; transition metal dichalcogenides