Pressure-Modulated Conductivity, Carrier Density, and Mobility of Multilayered Tungsten Disulfide

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• 作者：Avinash P. Nayak ; Zhen Yuan ; Boxiao Cao ; Jin Liu ; Junjie Wu ; Samuel T. Moran ; Tianshu Li ; Deji Akinwande ; Changqing Jin ; Jung-Fu Lin
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：9
• 期：9
• 页码：9117-9123
• 全文大小：501K
• ISSN：1936-086X

文摘

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 E_g of 鈭?.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 鈭?5 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鈥揗) transition at approximately 22 GPa at 280 K, which arises from the overlap of the highest valence and lowest conduction bands. The S鈥揗 transition is caused by increased sulfur鈥搒ulfur 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.