Temperature Dependence Of Decay Rate Research Articles

Temperature dependence of the anharmonic decay of optical phonons in carbon nanotubes and graphite

We report on the temperature dependence of the anharmonic decay rate of zone-center ($G$ mode) optical phonons in both single-walled carbon nanotubes and graphite. The measurements are performed using a pump-probe Raman scattering scheme with femtosecond laser pulses. For nanotubes, measured over a temperature range of 6 K--700 K, we observe little temperature dependence of the decay rate below room temperature. Above 300 K, the decay rate increases from 0.8 to 1.7 ps${}^{\ensuremath{-}1}$. The decay rates observed for graphite range from 0.5 to 0.8 ps${}^{\ensuremath{-}1}$ for temperatures from 300 K--700 K. We compare the behavior observed in carbon nanotubes and graphite and discuss the implications of our results for the mechanism of the anharmonic decay of optical phonons in both systems.

Spin relaxation of polarized Xe atoms stored in deuterated ethanol

We measured a spin relaxation of polarized xenon atoms in deuterated ethanol. The decay behavior depends on the magnetic dipole interaction and the electric quadrupole relaxation of deuterons. Though the cross-relaxation rate of deuteron with xenon was much less than that of proton, the enhancement of deuteron signal could be observed since the detection was performed at low magnetic fields. We define the figure of merit for a spin reservoir of solvent as the result of intensive investigation of the temperature dependence of decay rates and the solubility of xenon atoms in ethanol. For the long-term storage of a large number of polarized xenon atoms, it is important to take into account the viscosity of solvent which affects the translational motion as well as the decay time. By a time-resolved chemical-shift imaging, we observed the xenon atom acquiring its homogeneous distribution in viscous ethanol at low temperatures.

Temperature effects in the MONOS transistor

Metal-Oxide-Nitride-Oxide-Semiconductor (MONOS) memory transistors have been studied as a function of endurance cycling and elevated temperatures to determine the effects on memory window size and retention characteristics. Endurance cycling is shown to result in window loss and an increase in charge decay rate. Elevated temperatures enhance both of these degradation processes. However, following 10 9 cycles, the temperature dependence of decay rate is essentially masked by the damage caused by write/erase cycling. Following exposure to the most severe testing conditions (10 9 cycles at 175°C), the devices were still functional but the performance was significantly degraded.