通过离子插入二维材料的高效单轴面内拉伸( Highly Efficient Uniaxial In-Plane Stretching of a 2D Material via Ion Insertion )

Philipp K. Muscher Daniel A. Rehn Aditya Sood Kipil Lim Duan Luo Xiaozhe Shen Marc Zajac Feiyu Lu Apurva Mehta Yiyang Li Xijie Wang Evan J. Reed William C. Chueh Aaron M. Lindenberg 2D materials actuation electrochemistry in situ XRD intercalation structural analysis WTe2

Onヽhip dynamic strain engineering requires efficient micro゛ctuators that can generate large in﹑lane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1 V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful "straintronic" devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe2 causes large anisotropic in﹑lane strain: 5% in one in﹑lane direction and 0.1% in the other. This efficient stretching of the 2D WTe2 layers contrasts to intercalation﹊nduced strains in related materials which are predominantly in the out﹐f﹑lane direction. The unusual actuation of LixWTe2 is linked to the formation of a newly discovered crystallographic phase, referred to as Td , with an exotic atomic arrangement. Onヽhip low﹙oltage (<0.2 V) control is demonstrated over the transition to the novel phase and its composition. Within the Td ㎜i0.5δWTe2 phase, a uniaxial in﹑lane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in﹑lane chemical expansion coefficient of Td ㎜i0.5δWTe2 far greater than of any other single﹑hase material, enabling fast and efficient planar electrochemical actuation. Ion insertion in between the 2D layers of WTe2 is shown to induce an exotic crystallographic phase. This novel phase is linked to uniquely large uniaxial in﹑lane strain. Onヽhip electrochemical control over the lithium content in single flakes of WTe2 is demonstrated as an efficient, fast, and reversible way to control the strain, making LixWTe2 a promising microscale actuator.

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