Highly stable 2D material (2DM) field-effect transistors (FETs) with wafer-scale multidyad encapsulation

Area of Science:

• Materials Science
• Nanotechnology
• Electronics

Background:

• Two-dimensional materials (2DMs) like transition-metal dichalcogenides (TMDs) are highly sensitive to ambient air, particularly water adsorbates, leading to unstable electrical characteristics in field-effect transistors (FETs).
• Existing encapsulation methods have not been adequately explored for their effectiveness in protecting 2DM FETs from environmental degradation.

Purpose of the Study:

• To demonstrate the long-term retention of electrical characteristics in a molybdenum disulfide (MoS2) FET using a multidyad encapsulation method.
• To investigate the feasibility and effectiveness of multidyad encapsulation for 2DM FETs and determine the required water vapor transmission ratio (WVTR) for stability.

Main Methods:

• Fabrication of MoS2 FETs using both exfoliation and chemical vapor deposition (CVD) methods.
• Application of a multidyad encapsulation technique, comprising polymer layers (spin coating) and aluminum oxide (Al2O3) layers (atomic layer deposition - ALD).
• Primary investigation focused on exfoliated MoS2 FETs to isolate the encapsulation method's effectiveness.

Main Results:

• The multidyad encapsulation method demonstrated wafer-scale uniformity, high transparency, and excellent protective barrier properties against adsorbates.
• The encapsulated MoS2 FETs maintained stable electrical characteristics for one month.
• Achieved a low water vapor transmission ratio (WVTR) of 8 x 10^-6 g m^-2 day^-1.

Conclusions:

• The multidyad encapsulation method is effective in ensuring the long-term stability of MoS2 FETs in ambient air.
• This approach mitigates the high sensitivity of 2DMs to water adsorbates, paving the way for more robust 2DM electronic devices.
• The study validates the application of encapsulation techniques previously used for organic light-emitting diodes (LEDs) to 2DM FETs.