Volume 88, Issue 1, 01 July 2000
Index of content:
Measurement of thermal diffusivity based on the photothermal displacement technique using the minimum phase method88(2000); http://dx.doi.org/10.1063/1.373700View Description Hide Description
A method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as the radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the method are in good agreement with the literature values.
88(2000); http://dx.doi.org/10.1063/1.373701View Description Hide Description
The --type nanocompositemagnets have been prepared by hot pressing melt spun flakes under a conventional pressureP of 125 MPa and high pressures ranging from 1 to 7 GPa. It was found that increasing compaction pressure from 125 MPa to 5 GPa led to marked grain refinement in the magnet and consequently resulted in significant improvement of magnetic properties. When hot pressing under even higher pressure GPa), however, the crystallization was constrained and the hot pressedmagnets retained a certain amount of amorphous phase besides the -type phase and -(FeCo) phase, which resulted in the deterioration of the magnetic properties. A remanence of 11.1 kG, coercivity of 10.2 kOe, and maximum energy product of 23.6 MGOe have been achieved in the magnethot pressed under a pressure of 5 GPa.
88(2000); http://dx.doi.org/10.1063/1.373702View Description Hide Description
An analytic solution of the dissociative and the kickout diffusion mechanisms has been presented for a one-dimensional region bounded by two parallel surfaces, assuming the rapid recovery of equilibrium conditions of vacancies and interstitial matrix atoms. This assumption makes the diffusionequation linear. The calculation results for golddiffusion into a silicon plate with high dislocation density using the literature data are demonstrated. The assumption of the rapid recovery can be verified using the present solution.
88(2000); http://dx.doi.org/10.1063/1.373703View Description Hide Description
Persistent layer-by-layer removal of Au(111) during ion irradiation was observed in a real-time x-ray scattering study. Over 100 specular beam intensity oscillations were measured. For a given ion energy, a smoother surface morphology is obtained when the ion flux is reduced. For a fixed erosion rate, ion energy in the range of 70–500 eV does not have a strong influence on the evolution of surface morphology. Diffuse scattering measurements show the development of features with a characteristic lateral length scale on the surface during ion irradiation.
88(2000); http://dx.doi.org/10.1063/1.373704View Description Hide Description
The strain distribution and strain-induced confinement of carriers in quantum wires (QWRs) and quantum point contacts (QPCs) have been analyzed by elastic continuum and envelope wave function models. Recently, a compressive strain up to has been predicted to exist in the thermally oxidized surrounding the Si waveguide. We show that radial strain in the thermal oxide leads to lowering of the band edge inside the Si wire and to confinement of electrons in a quantum-dot-like potential having a depth of meV. The binding energy of the lowest electron level is −34 meV in a 240 nm long and 60 nm high QWR. The lowest energy level rises above the band edge in the contact pads when the QWR is made narrower than 12 nm. For the QPC, no bound states exist according to our calculations.