Thermal conductivity of multiwalled carbon nanotubes ͑CNT's͒ prepared using a microwave plasma chemical vapor deposition system is investigated using a pulsed photothermal reflectance technique. We find that the average thermal conductivity of carbon nanotube films, with the film thickness from 10 to 50 m, is around 15 W/m K at room temperature and independent of the tube length. Taking a small volume filling fraction of CNT's into account, the effective nanotube thermal conductivity could be 2ϫ10 2 W/m K, which is smaller than the thermal conductivity of diamond and in-plane graphite by a factor of 9 and 7.5, respectively.

Comparison of nitrogen compositions in the as-grown GaN[sub x]As[sub 1-x] on GaAs measured by high-resolution x-ray diffraction and secondary-ion mass spectroscopy

The plasmonic behavior of dimers of touching semiconductor disks is studied experimentally in the difficult‐to‐realize regime where the disks are only marginally overlapping. Previous theoretical studies have shown that this geometry exhibits a highly efficient broadband response that may be very promising for light harvesting and sensing applications. By taking advantage of the plasmonic character of InSb in the terahertz regime, we experimentally confirm this broadband response and describe the associated strong field enhancement and sub‐micrometer field confinement between the disks.

The photoluminescence of GaAs 0.973 Sb 0.022 N 0.005 was investigated at different temperatures, pressures, and excitation powers. Both the alloy band edge and the N-cluster emissions, which show different temperature and excitation power dependences, were observed. The pressure coefficients obtained in the pressure range of 0 -1.4 GPa for the band edge and N-related emissions are 67 and 45 meV/ GPa, respectively. The N-cluster emissions shift to higher energy in the lower pressure range and then begin to redshift at about 8.5 GPa. This redshift is possibly caused by the increase of the x-valley component in the N-related states with increasing pressure. A rapid decrease of the emission intensity of the N-related band was also observed when the pressure exceeded about 8 GPa.

A strained-modified, single-band, constant-potential three-dimensional model is formulated to study the dependence of electronic states of InAs/ GaAs quantum dots ͑QDs͒ on shape and size variation. The QD shapes considered are ͑i͒ cuboid, ͑ii͒ cylindrical, ͑iii͒ pyramidal, ͑iv͒ conical, and ͑v͒ lens shaped. Size variations include ͑i͒ QD volume ͑ii͒ QD base length, and ͑iii͒ QD height, taking into account aspect ratio variation. Isovolume QD shapes with narrow tips were found to have higher ground-state energies than those with broad tips, and this is attributed to the smaller effective volume. The volume, base length, and height dependencies were obtained and found to tally well with both experimental results and advanced calculations. Hence, upon growth parameter variation, this can provide an alternative to confirm whether the change to the size of the uncapped QDs implies a similar change to the capped ones. Ground-state energy as function of aspect ratio does not follow a monotonic trend. Owing to the competing effect of a decrease in base length and an increase in height, the energy trend exhibits a sharp decrease to an optimum aspect ratio, followed by gentle, almost linear increase. The optimum aspect ratio varies among shapes and is predicted to be smaller for shapes with broad tips. The effective volume ratio of both shapes ͑V eff,CUBOID / V eff,PYRAMID ͒ was determined, and found to vary with aspect ratio. Furthermore, a "cross-over" of lens-shaped QD from "lower energy" to "higher energy" group is predicted due to significant shape transition.