Fabrication and Detection Method for Attachment of CNTs to Nanoprobes
Original Publication Date: 2002-Aug-13
Included in the Prior Art Database: 2002-Aug-13
Theresa Hopson: AUTHOR [+5]
A self-monitoring method for the assembly of carbon nanotube (CNT) probes in a timely fashion exploits the software and piezo precision of a commercially available atomic force microscope (AFM) and eliminates problems associated with laborious mechanical approaches.
A self-monitoring method for the assembly of carbon nanotube (CNT) probes in a timely fashion exploits the software and piezo precision of a commercially available atomic force microscope (AFM) and eliminates problems associated with laborious mechanical approaches. A standard metal-coated silicon cantilever is brought into close proximity to vertically aligned chemical vapor deposited (CVD) grown CNT material, and by using the system’s internal bias source, a voltage step is applied between the probe and CNT sample in two steps to attach the CNT to the probe. Detection of CNT probe attachment utilizesthe built-in resonant tuning and force measurement capabilities of the AFM and thus eliminates the need for any subsequent electron beam inspection. With this technique we have been able to affix CNTs of widely varying dimensions with remarkably high yield and robustness. We suspect that metal particles (from the growth catalysis) that are incorporated inside the CNT aid in forming a eutectic bonding weld during the voltage pulse.
Spatially separated multi-walled nanotube material grown by CVD using a transition metal catalyst method was mounted atop a metal disc with silver epoxy ensuring contact from CNT base to carrier. The carrier was then secured to the sample chuck of the microscope with an adhesive carbon tape. Resistance of a few hundred ohms was measured between CNT and microscope ground. Metallized AFM probes were then mounted onto the cantilever holder where laser alignment and resonant frequency tuning were carried out per standard procedure. With the XY scan size set to zero and the scan rate at less than one hertz (Hz), the automated approach system was used to bring the AFM probe under TappingMode* imaging in air. Once in contact, a low negative voltage was applied (-5 V) for approximately 20 seconds to allow the CNTs to attract with favorab...