Dynamics of functional devices based on intercalated layered materials

Ling Lee^1*, Chun-Shou Chiang¹, Sueh-Liang Loo¹, Kuangye Wang¹, Yu-Lun Chueh¹

¹Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Ling Lee, email:leeling0430@gmail.com

Intercalations of foreign atoms into weakly bonded interlayers of two-dimensional (2D) materials have been utilized recently to modulate their intrinsic physical and chemical properties and open more feasibilities in diverse applications, such as exfoliation, catalysis, and energy storage. However, since typical intercalations are triggered in liquid phase, applications onto electronic devices are still not practical enough yet. In this work, several functional electronic devices based on 2D materials intercalated in solid-state and vapor-phase were demonstrated and the dynamics of working principles were also elucidated.
First, reversible and orientation-selective intercalation of copper were achieved in solid state memristors based on 1T-rich molybdenum diselenide (MoSe₂) as the basis of phase-changed memory. Once copper atoms are intercalated between vertical lamallar and vice versa via external bias with opposite polarities, a switching between the conducting 1T-phase and the semiconducting 2H-one occurs and causes the lateral two-terminals devices exhibiting resistance switchings of ratios approaching 100 after 100 cycles, powers of about 0.1 microwatt, and linear weight updates.
Second, nitrogen intercalations of MoSe₂ were also demonstrated by plasma-assisted post-selenization process, which partially deforms lattices and enlarges the work function. Once the intercalation is minor, the conduction band of MoSe₂ exceeds the reduction potential of NO₂, whereas large degree of nitrogen intercalation causes the valance band close to the oxidation potential of NH₃. Accordingly, electron extractions from MoSe₂ toward NO₂ molecules and donations from NH₃ molecules are individually promoted in the two opposite conditions, respectively, and result in a controlled gas selectivity between NH₃ and NO₂. In comparison to typical transition metal chalcogenides which is sensitive to NO₂ only, a ten times higher selectivity ratio against NH₃ than NO₂ was successfully demonstrated by the nitrogen intercalation.

Keywords: molybdenum diselenide, intercalation, phase change memory, gas sensor, selectivity