Browsing by Author "Ebrahimi, Mohamad"

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    Fabrication of Hybrid Atomic Force Microscopy Probe for Enhancing Sensitivity of AFM-Infrared Nanoscale Spectroscopy
    (2019-08-30) Ebrahimi, Mohamad; Kim, Seonghwan; Lee, Jihyun; Lu, Qingye
    Atomic force microscopy infrared-spectroscopy (AFM-IR) has emerged as a novel method that combines nanoscale resolution of AFM with IR-spectroscopy. In this technique heat generated by IR absorption within the sample will induce thermal expansion, which is detected by AFM probe, in contact with the sample, to discover the chemical composition of the sample based on IR absorption spectrum. One of the issues in applying this technique is that the heat generated in sample will also diffuse to the probe, due to thermal conduction which results in reducing the sensitivity of the probe. One of the alternative solutions to overcome this problem is to replace the AFM probe, which is commonly made by silicon, with a photopolymeric AFM probe. Since thermal conductivity of photopolymers are orders of magnitude lower than silicon, this alternative seems to be promising. To address this issue, I am developing a MEMS fabrication method enabling us to make a hybrid AFM probe (silicon cantilever with photopolymeric tip). Fabrication process starts with fixating a conventional AFM probe over a Petri dish with some photopolymeric resin which covers underneath of the cantilever. Secondly, I silanize the surface of the cantilever and then I replicate the tip of the cantilever using soft lithography with PDMS (Polydimethylsiloxane) to make a mold for tip fabrication. Finally, I cure a photopolymer inside the PDMS tip mold in contact with a silicon cantilever. I have utilized the hybrid probe in AFM imaging and AFM-IR spectroscopy over standard samples. Hybrid probes showed comparable results with standard silicon probes for AFM imaging. On the other hand, hybrid probes - in comparison with silicon probes - showed about 1.6 times increasement in signal to noise ratio in AFM-IR spectroscopy. Based on the measured results the sensitivity of AFM-IR technique has been improved utilizing hybrid probes.