Atomic Force Microscope and Carbon Nanotube Probes
Cattien V. Nguyen
NASA Ames Research Center
The atomic force microscope (AFM) and its many scanning force techniques are becoming increasingly important for the characterization and fabrication of nanomaterials, thus contributing to the general development of nanotechnology. At the heart of the AFM is the interaction between the scanning probe tip and sample substrate. The unique mechanical properties and nanometer scale diameter of carbon nanotubes (CNT) render CNT ideal as scanning probe tips. This presentation briefly reviews the various techniques for fabricating both single-walled and multi-walled CNT AFM tips, and some of the technical challenges facing these fabricating methods. Our unique fabrication technique produces very robust multi-walled carbon nanotube tips with a high aspect ratio (>1μm length and 10-20 nm diameter). In addition, a novel and simple tip sharpening technique has been developed to reduce the radius of curvature of the multi-walled carbon nanotube tips (radius < 5 nm). As the result, we now have highly robust carbon nanotube tips with the capability of imaging high aspect ratio features and higher lateral resolution. Data demonstrating the applications of the nanotube tips in a number of different scanning probe techniques, such as magnetic force, chemical force, semiconductor metrology, and liquid imaging of biopolymers will be presented. The carbon nanotube tips are electrically conductive so they are also ideal for application in scanning probe lithography (SPL). SPL, operated by passing an electrical current between the CNT tip and substrates while scanning, can form chemically patterned surfaces with nanometer accuracy. Subsequently, SPL with a nanotube tip offers a high resolution and precise means for nanomaterial deposition and opens up many possibilities for device fabrication. Data demonstrating SPL with CNT probes will also be presented.
Biography of Speaker
Cattien V. Nguyen is an alumnus of Santa Clara University (Chemistry 1988). After a year of graduate study at Brown University and two years as a scientist at IBM Almaden Research Center, he went on to obtain a Ph.D. in chemistry in 1996 from the University of California, Santa Cruz. His doctoral research was in bioinorganic chemistry, with focus on reaction mechanisms of metallo-enzymes. He then worked as post-doctoral fellow at Stanford University’s Department of Chemical Engineering, in collaboration with IBM Almaden Research Center. The research was on the chemistry and physics of photoresists, investigating the phenomenon of line-edge roughness in e-beam, x-ray, and photolithography. In 1997, with funding from NASA, Dr. Nguyen started on the development of nanoporous low-k dielectrics for on-chip interconnect applications. Since 1999, he has been at NASA Ames Research Center, where his research shifted to carbon nanotubes. His current interest lies in AFM and the development and applications of carbon nanotube tips for AFM. In addition to using the AFM and carbon nanotube tips for characterization, Dr. Nguyen is also exploring novel fabrication schemes employing AFM and carbon nanotube tips.