Paper NS-ThM3
STM and STS Studies of SWCNT on NaCl/Ag(100)

Thursday, October 18, 2007, 8:40 am, Room 616

Single-walled carbon nanotubes (SWCNTs) have been considered as one of the most promising candidates for future electronic devices due to their unique electrical properties. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have provided a lot of information about the structure and electronic properties of SWCNTs.^1,2 In most STM studies of SWCNT, it was carried out on metals or semiconductors so far. In these cases, the electronic structure of SWCNT can be perturbed by the presence of the electrons of the surface. For example, the charge transfer between metal substrate and SWCNT results in the shift of Fermi-level of SWCNT on Au(111) to the valence band.² In this study, we studied electronic structure of SWCNT on NaCl thin film by STM and STS. We introduced insulating layer to reduce the influence of metal surface. We deposited SWCNT on the NaCl(100) film, grown on Ag(100) single crystal by dry contact transfer technique in UHV.³ Interestingly, the Fermi-level of SWCNT shifted to the conduction band on Ag(100), while it shifted to the valence band on NaCl film. The charge transfer due to work function difference between Ag(100) (4.3eV) and SWCNT (4.8 ~ 5.0eV) was the main reason for the Fermi-level shift of SWCNT on Ag surface. On NaCl film, it is thought that the dipole moment at the interface between NaCl and Ag brought about Fermi-level shift to the conduction band, though the work function of NaCl on Ag(100) is 3.6 ~ 4.0eV, much lower than that of Ag(100). The influence of dipole moment on the electronic structure of SWCNT will be discussed in details.

¹ J.W.G. Wildöer, L.C. Venema, A.G. Rinzler, R.E. Smalley, and C. Dekker, Nature 391, 59 (1998).
² M. Ouyang, J.-L. Huang, and C.M. Lieber, Annu. Rev. Phys. Chem. 53, 201 (2002).
³ P.M. Albrecht and J.W. Lyding, Appl. Phys. Lett. 83, 5029 (2003).