Next generation of multifunctional scanning probes

AFM;SECM;Electrochemical sensor

Moon, Jong Seok ; Chemistry and Biochemistry

University:Georgia Institute of Technology

Department:Chemistry and Biochemistry

关键词: AFM;    SECM;    Electrochemical sensor;   

Others  :  https://smartech.gatech.edu/bitstream/1853/42935/1/moon_jongseok_201012_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

The goal of this thesis was the advanced design, fabrication, and application ofcombined atomic force microscopy - scanning electrochemical microscopy (AFMSECM)probes for high-resolution topographical and electrochemical imaging.The first part of the thesis describes innovative approaches for the optimization ofAFM-SECM probe fabrication with recessed frame electrodes. For this purpose,commercial silicon nitride AFM cantilevers were modified using optimized criticalfabrication processes including improved metallization for the deposition of the electrodelayer, and novel insulation strategies for ensuring localized electrochemical signals. As anovel approach for the insulation of AFM-SECM probes, sandwiched layers of PECVDSixNy and SiO2, and plasma-deposited PFE films were applied and tested. Usingsandwiched PECVD SixNy and SiO2 layers, AFM-SECM probes providing straight(unbent) cantilevers along with excellent insulation characteristics facilitating thefunctionality of the integrated electrode were reproducibly obtained. Alternatively, PFEthin films were tested according to their utility for serving as a mechanically flexibleinsulating layer for AFM-SECM probes. The electrochemical characterization of PFEinsulatedAFM-SECM probes revealed excellent insulating properties at an insulationthickness of only approx. 400 nm. Finally, AFM-SECM cantilevers prepared via bothinsulation strategies were successfully tested during AFM-SECM imaging experiments.In the second part of this thesis, disk-shaped nanoelectrodes were for the first timeintegrated into AFM probes for enabling high-resolution AFM-SECM measurements.Disk electrodes with an electrode radius < 100 nm were realized, which provides asignificantly improved lateral resolution for SECM experiments performed insynchronicity with AFM imaging. Furthermore, the developed fabrication schemeenables producing AFM-SECM probes with integrated disk nanoelectrodes atsignificantly reduced time and cost based on a highly reproducible semi-batch fabricationprocess providing bifunctional probes at a wafer scale. The development of a detailedprocessing strategy was accompanied by extensive simulation results for developing afundamental understanding on the electrochemical properties of AFM-SECM probes withnanoscale electrodes, and for optimizing the associated processing parameters. Thusfabricated probes were electrochemically characterized, and their performance wasdemonstrated via bifunctional imaging at model samples.The third part of this thesis describes the development and characterization of thefirst AFM tip-integrated potentiometric sensors based on solid-state electrodes with submicrometerdimensions enabling laterally resolved pH imaging. Antimony and iridiumoxides were applied as the pH sensitive electrode material, and have been integrated intothe AFM probes via conventional microfabrication strategies. The pH response of suchAFM tip-integrated integrated pH microsensors was tested for both material systems, andfirst studies were performed demonstrating localized pH measurements at a model system.