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High Aspect Ratio SPM Probe Development

Goal: To develop conductive high aspect ratio surface probes that can be used to measure critical dimensions of 3D geometries, as well as chemical and electrical surface properties.

Studies:

  • Fabrication of high aspect ratio probes with tunable geometries, and in collaboration with Xidex Corp., development of highly controllable carbon nanotube based SPM probes.
  • Elucidation of surface probe properties and capabilities, and utilization of the conductive nature of the probes for advanced electrical testing. 
  • Implementation of novel probes for surface analytical characterization including high resolution characterization of metal oxides and field effect transistors.
              

Fig 1. (top left) SEM micrograph of a CNT AFM tip welded to a sharpened W wire. (top right) Separation of the two probes causes CNT breakage, resulting in functional CNT AFM and STM probes. (bottom left) Linescan of a scatterometry grating imaged with a conventional probe (black trace) and a CNT AFM tip (red trace). (bottom right) High resolution STM image of highly oriented pyrolitic graphite acquired using a CNT STM probe.
                    
Significance: As the miniturization of electronic devices and features push further and further into the nanoscale world, advanced methods and instrumentation must be constantly improved to keep up with the demands of characterizing such small structures. One such instrument used in this nanoscale research, the atomic force microscope, relies on extremely sharp probes to accurately map the dimensions of nanoscale features. However, conventional probe designs are not capable of reliably evaluating the true morphology of these features. To overcome this shortcoming, our group is working to fabricate and test robust, high resolution high aspect ratio probes that can be tailor made for different sample applications. For instance, by utilizing the conductive nature of our probes as well as the capability to control orientation, length, and diameter, we can design probes that are capable of elucidating structural and electrical properties of  nanoscale features in a variety of environments.
Related Publications:
Williams, R. D.; Mancevski, V.; McClure, P.; Zhang, Z.; Li, S.-C.; Dohnalek, Z.; Stevenson, K. J. "Simultaneous Fabrication of Carbon Nanotube Atomic Force Microscopy and Scanning Tunneling Microscopy Tips Via Localized Chemical Vapor Deposition and Nanomanipulation," ACS Nano, submitted.

Nguyen, C. V.; Yi, Q.; Meyyeppan, M. "Carbon Nanotube Tips for Scanning Probe Microscopy: Fabrication and High Aspect Ratio Nanometrology," Measurement Science and Metrology, 2005, 16, 2138.

Koley, G.; Spencer, M. G.; Bhangale,  H. R. "Cantilever Effects on the Measurement of Electrostatic Potentials by Scanning Kelvin Probe Microscopy," Applied Physics Letters, 2001, 79(4), 545.

McEvoy, T. M.; Stevenson, K. J. “Spatially-Resolved Imaging of Inhomogeneous Ion/Charge Transfer Behavior in Polymorphous MoO3. I. Correlation of Localized Structural, Electronic, and Chemical Properties Using Conductive Probe AFM and Raman Microscopy,”Langmuir, 2005, 21(8), 3521.
Students currently involved in this project: Hugo Celio, Ryan Williams