January 2008

EEEL Researchers Develop New Measurement Technique for Carbon Nanotubes

EEEL Researchers Katie Hurst and John Lehman, along with collaborators Richard Ahrenkiel and Tom Campbell, have developed a new technique for measuring the recombination lifetimes of carbon nanotubes (CNT) called the resonant-coupled photoconductive decay (RCPCD) method. The carrier recombination lifetime is a fundamental property of carbon nanotubes that is typically determined by contact-based techniques or spectroscopic methods. These methods do not readily allow for the characterization of bulk material properties. The new measurement technique is based on a pump-probe technique (1) in which an optical pump and a low frequency microwave probe are employed. RCPCD offers the first rapid, non-contact technique for routine nanometrology of carbon nanotube electronic properties.

The researchers conducted measurements of carrier lifetimes for multi-walled and single-walled CNT thin films. The thin films were made by depositing a ~30 micrometer thick CNT coating on a glass slide by an air-brush technique. The researchers also considered the influence of material purity on the measurement of lifetimes in these nano-scale systems. Raman spectroscopy and UV-VIS absorption measurements provide further identification and characterization of nanotube samples to enable correlation of nanotube properties with the efficiency of charge transport in these samples. RCPCD is shown to be a fast and effective method for measuring the lifetimes of bulk carbon nanotubes, thereby overcoming present issues of routine carbon nanotube electronic nanometrology. This work was presented at the recent 54th American Vacuum Society International Symposium and Exhibition in Seattle.
(1) R.K. Ahrenkiel, S.W. Johnston Mater. Sci. Eng. B 102 (2003) 161.

Contact: Katie Hurst, phone 303-497-4884