Figure 1

Scanning electron micrograph of nanotubes on pillars. An array of silicon pillars is shown from an angle ($\sim 30°$). Single walled nanotubes are clearly seen bridging the pillars. On close inspection, some tubes lying on the surface below can also be seen.Reuse & Permissions

Figure 2

Photoluminescence spectra: ($a$) from the pillar areas of an argon-only control sample; (b) on flat areas of a methane CVD sample with abundant nanotubes; ($c$) on pillar areas of methane CVD samples with bridging nanotubes. Spectra were taken at room temperature in air with the $\mu \mathrm{P}\mathrm{L}$ configuration (see text), using a HeNe laser (633 nm) at 1.7 mW, with a $2\mu \mathrm{m}$ diameter spot.Reuse & Permissions

Figure 3

Excitation wavelength dependence of photoluminescence spectra. Photoluminescence spectra are shown for a series of excitation wavelengths. Spectra were taken at room temperature in air with the MPL configuration using various lasers (see text). A $100\mu \mathrm{m}$ spot diameter and an average power of 1.7 mW was used in all cases. Each spectrum is offset along the $y$ axis by an amount proportional to the excitation wavelength. The same laser power and collection optics were used for all spectra so the intensity can be compared for different curves. The thick grey band highlights the expected PL resonance. The black vertical lines highlight PL peaks which are resonant. The dotted and dashed lines trace the $G^{\prime }$ and $G$ Raman modes, respectively.Reuse & Permissions