Jul 10, 2009
Carbon nanotubes shaped for high-resolution spm
Scientists in Taiwan have used UHV STM/TEM apparatus configured with 3D movable holders to refine the fabrication of carbon nanotube (CNT) probes with sub-nanometre precision. The set-up's tailoring functions include length control, contaminant removal, apex trimming and in situ welding, which can be used to optimize CNT probes for scanning probe microscopy applications.
Scanning tunnelling microscopy (STM) and transmission electron microscopy (TEM) are two well-known atomic imaging techniques. The combination of these two microscopies, deriving from the concepts of nano-eye in STM and nano-finger in TEM, provides in situ observation and measurement to accompany the growth and manipulation of nanostructures. For example, the above HRTEM picture (left), in comparison with the simulated scheme (right), depicts how the group uses the STM@TEM functionality to tailor an ultrasharp CNT apex to approach the dimensions of a single-walled CNT.
A key advantage of the team's set-up is that the entire experiment can be operated in a UHV chamber (< 3 x 10–10 mbar), which reduces the exposure of the manipulated nanostructures to contaminants. In addition, the synchronous control can eliminate unexpected damage that can occur during sample transfer.
In their recent paper, the researchers describe in detail how to fabricate CNT probes using the UHV technique and highlight the advantages of their approach compared with conventional methods. The prominent probe quality has routinely led to a good resolution in SPM measurements, such as <5 nm for AFM and <10 nm for EFM (see earlier work).
The group presented its work in Nanotechnology.
About the author
Shu-Cheng Chin is a research assistant in the Surface and NanoScience Laboratory, Institute of Physics, Academia Sinica (IPAS), Taiwan, where he is working on the application of CNT probes in scanning probe microscopy. Yuan-Chih Chang received his PhD degree from the National Yunlin University of Science & Technology in 2004. He is now a post-doctoral research fellow based at IPAS, where he succeeded in the development of nanostructure manipulation methods using an integrated 3D two-probe UHV TEM system. Prof. Chia-Seng Chang is a faculty research fellow based at IPAS. His research interests focus on the STM study of quantum size phenomena within cluster and thin film growths, the AFM as a DNA manipulation tool in molecular biology, and UHV TEM techniques.