Zhang Cheng, Zhao Wei, Bi Sheng, Rouleau Christopher M, Fowlkes Jason D, Boldman Walker L, Gu Genda, Li Qiang, Feng Guang, Rack Philip D
Department of Materials Science and Engineering , University of Tennessee , Knoxville , Tennessee 37996 , United States.
Center for Nanophase Materials Sciences , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.
ACS Appl Mater Interfaces. 2019 May 15;11(19):17979-17986. doi: 10.1021/acsami.9b02373. Epub 2019 May 6.
Ionic liquids (ILs) have been investigated extensively because of their unique ability to form the electric double layer (EDL), which induces high electrical field. For certain materials, low-temperature IL charging is needed to limit the electrochemical etching. Here, we report our investigation of the low-temperature charging dynamics in two widely used ILs-DEME-TFN and Cmim-TFN. Results show that the formation of the EDL at ∼220 K requires several hours relative to milliseconds at room temperature, and an equivalent voltage V is introduced as a measure of the EDL formation during the biasing process. The experimental observation is supported by molecular dynamics simulation, which shows that the dynamics are logically a function of gate voltage, time, and temperature. To demonstrate the importance of understanding the charging dynamics, a 140 nm thick FeSeTe film was biased using the DEME IL, showing a tunable T between 18 and 35 K. Notably, this is the first observation of the tunability of the T in thick film FeSeTe superconductors.
