Optoelectronics with Carbon Nanotubes
Optoelectronics with Carbon Nanotubes
Optoelectronics with Carbon Nanotubes
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3. Conclusions<br />
We have examined the intensity and spectral shapes of EL from single-tube CNTFETs.<br />
From transport measurements, it is seen that their electrical transfer depends on the control of<br />
Schottky barriers at metal contacts. In agreement <strong>with</strong> an impact-excitation process of exciton<br />
generation, a threshold behavior is observed at the EL onset. The very broad lineshape of the E11<br />
transition is attributed to tube non-homogeneity, phonon scattering, electronic heating, and the<br />
effect of external electric field in the longitudinal direction. There is evidence that phonon<br />
temperatures (and <strong>with</strong> it, possibly electron temperatures) saturate at very high input power,<br />
possibly because of the energy dissipation by the EL mechanism.<br />
We have observed E11 and E22 peaks, defect-mediated E11 peak, and the E11 - optical<br />
phonon side band complex. In polarized measurements, a clear suppression of E11 and E22 peaks<br />
is observed in the perpendicular direction. Conversely, we were able to observe the E12<br />
transition for the first time in EL by investigating perpendicularly polarized component of the<br />
emission.<br />
Our data point to possible future explorations that include phonon and electron<br />
temperature measurements, a more detailed investigation of the broadening mechanisms, and a<br />
realization of better signal-to-noise ratio for superior spectroscopic data. While polarized EL<br />
from CNT may have interesting applications in future nano-scale optoelectronics, there are many<br />
issues, especially in carrier and phonon dynamics and their interactions, that still need to be<br />
better understood.<br />
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