Atomic deuterium bonding to multi-walled carbon nano tubes

Atomic deuterium adsorption on multi-walled carbon nanotubes (MWCNTs) has been achieved with a high deuteration level (≃70% of deuterated carbon atoms), and studied using complementary spectroscopic techniques, namely, photoelectron spectroscopy and Raman spectroscopy. As a consequence of the deuterium (D) adsorption on the MWCNTs, the sp2 bonds of the C atoms are distorted toward an sp3 configuration, and the π plasmon excitation of the metallic MWCNTs is quenched, suggesting the transition to a semiconducting phase. Such a controlled deuteration in ultra-high vacuum conditions induces the opening of an energy gap in the metallic MWCNTs, with the valence band maximum at about ∼3.1 eV below the Fermi level. The bond distortion and the strain induced by the D uptake is evidenced by the modification of the Raman response. This work shows that the molecular cracking of D2 in ultra-high vacuum is an efficient way to obtain stable, homogeneous, and high uptake of deuterium atoms with minimal presence of defects.