DEVELOPMENT OF A NANOGAP FABRICATION METHOD FOR APPLICATIONS IN NANOELECTROMECHANICAL SYSTEMS AND NANOELECTRONICS
Anıl Günay Demirkol
Physics, Ph.D. Dissertation, 2013
Assoc. Prof. İsmet İnönü Kaya (Thesis Supervisor), Assoc. Prof. Mehmet Zafer Gedik, Assoc. Prof. Ayhan Bozkurt, Prof. Dr. Ahmet Oral, Assoc. Prof. Kaan Güven
Date & Time: January 28th, 2013 – 14:00
Place: FENS L048
Keywords: Nanogap, Vacuum Tunnel Junction, Controlled Thermal Evaporation, High Tensile Stress Thin Films, NEMS
There is a great need for a well-controlled nanogap fabrication technique compatible with NEMS applications. Theoretically, a displacement sensor based on vacuum tunnel junction or a nanogap can be capable of performing quantum-limited measurements in NEMS applications. Additionally, in the context of nanoelectronics, nanogaps are widely demanded to characterize nanostructures and to incorporate them into nanoscale electronic devices. Here, we have proposed and implemented a fabrication technique based on the controlled shrinkage of a lithographically defined gap between two suspended structures by thermal evaporation. We have consistently produced rigid and stable metallic vacuum tunneling junctions at nanometer or sub-nanometer sizes. The fabricated nanogaps were characterized by I-V measurements and their gap sizes and potential barrier heights were interrogated using the Simmons’ model. Throughout this work, high tensile stress silicon nitride thin films were preferred for the fabrication of suspended structures because they have high resonance frequencies with low dissipation, they are mechanically stable, and they are resilient to stiction problem. However, high-stress nitride structures experience a complex shape deformation once they are suspended. The shape deformation is undesired when the precise positioning of the structures is required as in nanogap fabrication. We developed a new method in which the built in stress gradient is utilized to tune the distance between two suspended structures. The technique was simulated by finite element analysis and experimentally implemented to demonstrate a gap tuning capability beyond the lithographic resolution limits.