Dynamics of functional devices based on intercalated layered materials
Ling Lee1*, 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