Candidate: Ferhat Aydinoglu
Title: Fabrication of high aspect ratio (HAR) atomic force microscopy (AFM) probes by one step e-beam lithography and AFM cantilever patterning using grafted monolayer
Date: October 3, 2018
Time: 2:00 PM
Place: EIT 3142
Supervisor(s): Cui, Bo
Abstract:
Atomic force microscopy (AFM) allows imaging individual atoms where a very sharp tip touches and feels the substrate. Although a regular AFM tip can achieve atomic resolution, it produces false images on substrates with tall and dense features because of the shape and dimensions of the tip. To solve this problem, high aspect ratio (HAR) AFM tips have emerged. However, the HAR AFM tips are often fabricated individually with the need of expensive instruments such as focused ion beam causing low throughput and high cost. In this thesis, several processes are developed for batch fabrication of HAR AFM tips to reduce the cost and increase the throughput where HAR tips with down to 9 nm tip apex diameter without oxidation sharpening has been obtained by our methods. Moreover, there are cantilever-based devices demanded in a wide range of applications such as tip enhanced Raman spectroscopy.
Our one-step e-beam lithography technique is capable of forming arbitrary patterns for a variety of applications. Alternatively, a process based on grafting polystyrene monolayer brush has been developed to pattern irregular substrates like cantilevers with e-beam lithography where both negative and positive tone behaviors are obtained under different development conditions. That is, the process allows both recessed and protruded feature fabrication on nonflat and very small surfaces. As a result, an AFM cantilever is patterned with high resolution on both top and sidewalls at the same time.