Integration of Two-Dimensional Materials for Electronics and Photonics
Time: Wed 2022-06-15 14.00
Location: F3, Lindstedtsvägen 26 & 28, Stockholm
Subject area: Electrical Engineering
Doctoral student: Arne Quellmalz , Mikro- och nanosystemteknik
Opponent: Dr. Cedric Huyghebaert, Interuniversity Microelectronics Centre (IMEC)
Supervisor: Kristinn Gylfason, Mikro- och nanosystemteknik; Frank Niklaus, Mikro- och nanosystemteknik
Two-dimensional (2D) materials with a thickness on the atomic scale promise to continue the trend of increasing performance in electronics, photonics, and sensing. However, despite record-breaking demonstrations of individual devices, the commercial exploitation of 2D materials is still limited. This constraint is partly because of challenges in integration technologies for manufacturing devices.
This thesis presents manufacturing methods of transferring and patterning 2D materials. On the device level, it investigates the influence of environmental factors on electrical contacts and material properties. Finally, it demonstrates the integration of photodetectors for integrated photonic circuits.
The synthesis of 2D materials requires high process temperatures to obtain high material quality, which precludes the direct synthesis on top of device wafers. Thus, manufacturing requires a transfer of the 2D material from a dedicated growth substrate to the device wafer.This thesis introduces a universal method of transferring 2D materials by wafer bonding. The method targets the integration on top of electronic circuits at the back-end of the line in semiconductor foundries. A variation of the approach suspends free-hanging membranes of 2D materials and stacks layers to 2D material heterostructures.
The patterning of 2D materials is a fundamental step in device fabrication. However, standard lithographic methods cause residues of protective resists that degrade the device performance. This thesis presents a non-contact and resist-free method of patterning 2D materials with nanoscale precision by laser direct writing with an off-the-shelf system.
The electrical contact resistance between metal electrodes and 2D materials significantly affects the performance of devices. This thesis investigates the influence of humidity on the contact resistance and sheet resistance of graphene. This insight is essential for operation in ambient environments without encapsulation or hermetic packaging.
Multilayered platinum diselenide (PtSe2) is a semimetallic 2D material that can be synthesized below 450 degree Celsius. This thesis demonstrates the integration of PtSe2 photodetectors with silicon waveguides by direct growth on the device substrate. The photodetectors operate at infrared wavelength, which is promising for integrated photonic circuits.