Fig. 4 | Nature Communications

Fig. 4

From: Ultra-narrow-band near-infrared thermal exciton radiation in intrinsic one-dimensional semiconductors

Fig. 4

Emission spectra of thermally excited nanotubes. a, b High-temperature radiation spectra of the (18,8) semiconducting (a) and (30,12) metallic (b) nanotubes around 1400 K, respectively. The bottom axes show the differences from the peak photon energy (EP − E0). The black solid curves and the gray dotted curves show the calculated results (see Methods for detailed spectral analyses). The inset shows the calculation models based on exciton (a) and free electron–holes in one-dimensional joint density of states (b). c, d Radiation spectra of the semiconducting (c) and metallic (d) nanotubes around 2100 K. The inset shows the dispersion relations of excitons and photons in the exciton picture (c) and those of the conduction band (CB) and valence band (VB) in the free electron–hole picture (d). The shaded regions indicate the energy–momentum states of excitons, electrons, and holes that can be involved in the radiative transitions (vertical arrows). e The high-temperature radiation (red curve) and Rayleigh scattering (purple curve) spectra of the (18,8) semiconducting nanotube at various temperatures. The spectra are vertically offset for clarity. Rayleigh scattering spectra could be measured up to ~970 K, and the high-temperature radiation spectra could be observed above ~970 K. In the high-temperature radiation region (>~1000 K), Rayleigh spectra could hardly be measured. The orange curve is a guide to the eye

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