Development of MEMS-Based Devices for Characterizing 2D Nanomaterials at Low Temperatures

Investigates the mechanical and electronic properties of two-dimensional nanomaterials under strain, addressing gaps in the existing literature. The primary challenge with these materials is the inconsistent application of high strain rates and the absence of experimental data at low temperatures. To overcome these challenges, we develop Microelectromechanical Systems (MEMS)-based devices for characterizing 2D nanomaterials and semiconductor materials at low temperatures. Four MEMS-based devices are developed to facilitate this characterization. The first device is a unique MEMS testing platform with on-chip actuation, sensing, and feedback control systems, capable of applying controlled displacements to nanoscale specimens while minimizing temperature fluctuations. To achieve this, MEMS thermal actuators with an axial stiffness of 40253.6 N/m are used. Capacitive sensors and V-beam amplification mechanisms are designed for precise measurement. The second device, the cascaded MEMS device, employs horizontal and vertical V-shaped structures to measure stress-strain curves of 2D nanomaterials at low temperatures. The third device is a customized MEMS electrostatic actuator for bending tests on silicon material under low-temperature conditions. Finally, two MEMS rotational structures, including a novel C-shaped structure, are developed to amplify movement. The MEMS devices are fabricated using bulk micromachining and deep reactive-ion etching (DRIE) with silicon-on-insulator (SOI) wafers, incorporating underpass technology for electrical isolation within the MEMS-based testing platforms. To optimize DRIE etching parameters for creating underpass islands in SOI MEMS, a study was conducted considering a total of nine wafers, divided into two batches for fabrication process, and examining their behavior concerning the etching process. The devices are optically characterized at room temperature and tested in a vacuum environment and at low temperatures using scanning tunneling microscope (STM) tool.