Volume 104, Issue 4, 15 August 2008
Index of content:
104(2008); http://dx.doi.org/10.1063/1.2968209View Description Hide Description
We employ a microprobe photoluminescence(PL) technique to determine the thermal resistance and wall-plug efficiency of narrow-ridge interband cascade lasers emitting at . Using two different semiconductor epilayers as integrated thermometers, the local lattice temperature is extracted from the PL spectra and the wall-plug efficiency derived from the slope of the temperature increase versus electrical power. The maximum at 78 K is found to be , and a fit to the lattice temperature gradient implies cross-plane thermal conductivities of for the short-period InAs/AlSb superlatticecladding and of for the active region.
104(2008); http://dx.doi.org/10.1063/1.2969056View Description Hide Description
A new ferroelectricsolid solution of (PT) has been synthesized in the form of ceramics by solid-state reactions and characterized by means of x-ray diffraction, ferroelectric measurements, and dielectric spectroscopy. All ceramics with different compositions crystallize in the pure perovskite phase. With increasing PT content, the properties of ceramics gradually transfer from dielectrics to relaxors, and then to normal ferroelectrics. Based on the x-ray and dielectric measurements, a partial phase diagram of the system is established, which exhibits a morphotropic phase boundary with compositions .
104(2008); http://dx.doi.org/10.1063/1.2969053View Description Hide Description
Structural and electronic properties of NiO in the zinc-blende (zb) structure have been studied by ab initio calculations based on density functional theory. The results show that zb-NiO has a half-metallic band structure and its lattice constant is compatible to that of wide gap semiconductors such as SiC, GaN, and ZnO. The half-metallic character can survive the in-plane strain from the wide gap semiconductor substrates. Thus, our calculations indicate that NiO can be a potential half metal for these wide gap semiconductors for spin injection.
Surface roughness influence on parametric amplification of nanoresonators in presence of thermomechanical and environmental noise104(2008); http://dx.doi.org/10.1063/1.2970108View Description Hide Description
We investigate the surface roughness influence on the gain from parametric amplification in nanoresonators in the presence of thermomechanical and momentum exchange noise. The roughness is characterized by the rms amplitude , the correlation length , and the roughness exponent . It is found that the gain strongly increases with increasing roughening (decreasing and/or increasing ratio ) due to the increment in capacitive coupling, which plays a dominant role when the intrinsic quality factor is comparable or lower than the quality factor due to gas collisions. However, for , the influence of surface roughness on the gain strongly diminishes.