Volume 84, Issue 7, 01 October 1998
Index of content:
84(1998); http://dx.doi.org/10.1063/1.368583View Description Hide Description
Photoluminescence coupled with repetitive thermal annealing has been used to study the interdiffusion process in a 10 nm single quantum well. The diffusion equations and the Schrödinger equation were solved numerically to obtain the composition profile and the electron to heavy-hole transition energies in the intermixed quantum well, respectively. The intermixing process was shown to obey Fick’s second law.
84(1998); http://dx.doi.org/10.1063/1.368584View Description Hide Description
The Boltzmann equation was solved exactly for the case of low-field electron transport in bulk GaN at 300 K in the presence of polar-optical phononscattering only, giving a mobility at low electron densities of 2200 or 2500 The effect of increasing the electron concentration to around was found to reduce the mobility to 640 . This new result was shown to be a consequence of there being at high densities, a greater proportion of electrons able to emit phonons.
84(1998); http://dx.doi.org/10.1063/1.368585View Description Hide Description
We report on a temperature dependence of the frequency of all the major peaks in the Raman spectra of carbon nanotubes, using different excitation laser powers at the sample. The frequency decreases with increasing temperature for all peaks, and the shifts in Raman frequencies are linear in the temperature of the sample. In comparison, a similar dependence is found in active carbon, but no shift is observed for the highly ordered pyrolytic graphite within the same range of variation in laser power. A lowering of frequency at higher temperature implies an increase in the carbon–carbon distance at higher temperature. The relatively strong temperature dependence in carbon nanotubes and active carbon may be due to the enhanced increase in carbon–carbon distance. This enhancement may originate from the heavy defects and disorder in these materials.