Volume 109, Issue 5, 01 March 2011
Index of content:
109(2011); http://dx.doi.org/10.1063/1.3554624View Description Hide Description
Magnetic measurements up to 1000 K have been performed on hydrothermally synthesized α-Fe2O3 nanoparticles (60 nm) using a Quantum Design vibrating sample magnetometer. A high vacuum environment (1×10−5 Torr) during the magnetic measurement up to 1000 K leads to a complete reduction of α-Fe2O3 to Fe3O4. This precludes the determination of the Néel temperature for the α-Fe2O3 nanoparticles. In contrast, coating α-Fe2O3 nanoparticles with SiO2 stabilizes the α-Fe2O3 phase up to 930 K, which allows us to determine the Néel temperature of the α-Fe2O3 nanoparticles for the first time. The Néel temperature of the 60-nm α-Fe2O3 nanoparticles is found to be 945 K, about 15 K below the bulk value. The small reduction of the Néel temperature of the α-Fe2O3 nanoparticles is consistent with a finite-size scaling theory.
109(2011); http://dx.doi.org/10.1063/1.3554673View Description Hide Description
Carrier profiles of quantum wells, obtained from experimental capacitance-voltage (C-V) measurements match the theoretically simulated carrier profile quite closely but these are much different from the actual carrier profile. It is observed that the peaks of the experimental and simulated carrier profiles move in the opposite direction and at low temperature there nature changes drastically. These observations have been explained taking into account the two dimensional carrier confinement and its temperature dependence through self-consistent solutions of the Schrödinger and Poisson equations. The effect of the series resistance seems to be highly pronounced in experimental C-Vmeasurements.
The channel mobility degradation in a nanoscale metal–oxide–semiconductor field effect transistor due to injection from the ballistic contacts109(2011); http://dx.doi.org/10.1063/1.3554623View Description Hide Description
The ballisticmobility degradation is shown to originate from nonstationary (transient) transport in response to the ohmic electric field. The source and drain reservoirs launch electrons into the channel with injection velocity transiting the channel with finite ballisticity defined as the probability of a collision-free flight. The distinction is made between the ballistic mean free path and that present in a long channel. The results are in excellent agreement with those obtained from Monte Carlo procedures and experiments.
109(2011); http://dx.doi.org/10.1063/1.3562137View Description Hide Description
The plasma absorption effects on the collisions of positively charged dust grains are investigated in dusty plasmas. The method of stationary phase and the effective interaction potential containing the attractive part are employed to obtain the scattering cross-section between a pair of positively charged dust grains as a function of the impact parameter, collision energy, electron and ion temperatures, and Debye length. The result shows that the plasma absorption effects on the dust surface strongly suppress the total scattering cross-section. It is also shown that the plasma absorption effects on the scattering cross-section decrease with an increase of the ratio of the electron temperature to the ion temperature. In addition, the plasma absorption effects are found to be decreased with increasing the collision velocity.