Ion Desorption from Single-Walled Carbon Nanotubes Induced by Soft X-ray Illumination

Abstract

We have investigated ion desorption from single-walled carbon nanotubes (SWNTs) that is induced by soft X-ray illumination in the C 1s core-excitation energy range in order to have insight to the mechanism of defect formation caused by the similar excitation. The mass of desorbed ions was analyzed by a time of flight (TOF) spectrometer and the photon energy 2 dependence of the ion yield or the desorption efficiency spectra were measured as a function of the monochromatic photon energy used for illumination. Experimental results exclude the simple detachment of carbon atoms constituting the nanotubes from the cause of the defect formation.Also the photo-induced etching of carbon atoms associated with C-H bond rapture is ruled out from the defect formation mechanism. Auger mechanisms to explain the photo-induced desorption are discussed.

Low-Energy Irradiation Damage in Single-Walled Carbon Nanotubes

“…Recently, Mera et al directly measured ion desorption from SWCNTs under soft X-ray illumination (Mera et al, 2010). They also excluded emission of carbon atoms from the SWCNTs.…”

“…The low-energy irradiation damage has been observed in a surface-science-grade ultra-high vacuum (UHV) of 1×10 -8 Pa by VUV light illumination (Suzuki & Kobayashi, 2006a. Suzuki & Kobayashi, 2007a. Mera et al, 2010, electron beam irradiation , and electron (hole) injection from a STM tip (Berthe et al, 2007.…”

Structural change induced in carbon materials by electronic excitations

“…As mentioned in section 2, Coulomb explosion cold take place because the localized multiple holes generated also in the normal Auger final states have a relatively long lifetime [15]. In fact, the desorption efficiency spectrum in SWNTs obtained by dividing total counts of desorbed ions with the counts of normal Auger electrons of 259 eV in energy exhibits a non-resonant feature at energies higher than 290 eV [26]. Nevertheless, there could be another scenario that low-energy electrons generated as secondary products of core excitations are responsible for the non-resonant damage.…”

“…To examine these hypotheses, we conducted TOF measurements of photo-desorbed species at KEK-PF [25,26]. The ta-C sample we used was basically the same as that used for illumination experiments at SPring-8.…”