Surface analysis of a well-aligned carbon nanotube film by positron-annihilation induced Auger-electron spectroscopy

Positron-annihilation induced Auger-electron spectroscopy (PAES) was used to study the surface of a well-aligned carbon nanotube film grown on a Si substrate. Since the nanotubes are aligned perpendicular to the substrate, the surface analysis of the film provides information on the tip of the nanotube. We compared the Auger spectra obtained by PAES and 3 keV electron-induced AES (EAES) and found that PAES has an extremely high sensitivity to small quantities of impurities such as Cl, N, and O. The result can be explained by the fact that the positrons implanted at low energy (50 eV) have high probabilities of being trapped by the impurities adsorbed at the tip of the nanotubes. Depth-resolved positron lifetime spectroscopy and Doppler-broadening spectroscopy were also carried out to get information on the depth profiles of defects and impurities in the carbon nanotube (CNT) film.

[1]  Zettl,et al.  Extreme oxygen sensitivity of electronic properties of carbon nanotubes , 2000, Science.

[2]  S. Iijima.  Helical microtubules of graphitic carbon , 1991, Nature.

[3]  N. Shiotani,et al.  Stretching of slow positron pulses generated with an electron linac , 1990 .

[4]  Lynn,et al.  Increased Elemental Specificity of Positron Annihilation Spectra. , 1996, Physical review letters.

[5]  Liming Dai,et al.  Patterned Growth and Contact Transfer of Well-Aligned Carbon Nanotube Films , 1999 .

[6]  Zhu,et al.  Adsorption and desorption of an O2 molecule on carbon nanotubes , 2000, Physical review letters.

[7]  M. Dresselhaus,et al.  Carbon nanotubes : synthesis, structure, properties, and applications , 2001 .

[8]  R. Suzuki,et al.  Slow Positron Pulsing System for Variable Energy Positron Lifetime Spectroscopy , 1991 .

[9]  Y. Kobayashi,et al.  Direct evidence of positron trapping at polar groups in a polymer-blend system , 1999 .

[10]  Lynn,et al.  Auger-electron emission resulting from the annihilation of core electrons with low-energy positrons. , 1988, Physical review letters.

[11]  T. Ohdaira,et al.  High sensitivity of positron-annihilation induced Auger-electron spectroscopy to surface impurities , 1996 .

[12]  Y. Kawazoe,et al.  Stable Vacancy Clusters in Neutron-Irradiated Graphite: Evidence for Aggregations with a Magic Number , 1999 .

[13]  T. Ohdaira,et al.  Apparatus for positron-annihilation-induced Auger electron spectroscopy with a pulsed positron beam , 1996 .