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Photoluminescence (PL) spectroscopy is one of the important analysis techniques for the optical properties of single-walled carbon nanotubes (SWNTs). However, PL spectra are measured only from surfactant-wrapped SWNTs [1], suspended SWNTs [2], and vertically-aligned SWNTs [3]. For optical and opto-electronic applications of SWNTs, SWNTs which lie on substrates and emit PL signal are needed. In this study, SWNTs were directly synthesized on hexagonal boron nitride (h-BN) substrates and PL spectroscopy was performed. h-BN is a suitable substrate for SWNTs because it has large band gap and its surface is atomically flat [4]. By using mechanical exfoliation technique, multilayered h-BN was obtained on silicon substrates. Iron metal particles and ethanol were used as the catalyst and carbon source of SWNT growth, respectively. Figure 1 shows (A) PL spectrum and (B) PL map obtained from SWNTs on h-BN. Relatively sharp PL emission was measured. It is known that the optical transition energy (Eii) of SWNTs depends on the surrounding conditions. The E11 and E22 of SWNTs on h-BN were almost the same as those of surfactant-wrapped SWNTs, and PL map, as shown in Fig. 1(B), exhibited that the chirality was (9,5).
[1] S. M. Bachilo, et al., Science 298, 2361 (2002).
[2] J. Lefebvre, et al., Phys. Rev. Lett. 90, 217401 (2003).
[3] O. Kiowski, et al., Phys. Rev. B 75, 075421 (2007).
[4] N. A Lanzillo, N. Kharche and S. K. Nayak, Sci. Rep. 4, 3609 (2014).
[5] S. Chiashi, S. Watanabe, T. Hanashima, Y. Homma, Nano Lett. 8, 3097 (2008).
