Amorphous silicon is the most popular material in the field of semiconductors. However, little is known about its microstructures. To understand the dependence of these microstructures on the fabrication process and on structural relaxation, amorphous silicon samples fabricated by various simulated processes are classified according to structural parameters within the molecular dynamics method.
The results show that the amorphous structures fabricated by the melt-quench method have many odd-membered rings and large bond-angle deviation. The structures fabricated by the molecular-beam epitaxy method involve fewer floating bonds, smaller bond-angle deviations, and fewer six-membered rings in comparison with the melt-quenched structure. Through long-term annealing, both structures are transformed to the most stable structure as described by the Tersoff potential. It is also found that the continuous random network structure does not meet the Tersoff potential. Verification of the results through first-principle calculations shows that well-relaxed amorphous structure can be described by classical molecular dynamics despite the slightly large number of the floating bond and the overestimation of amorphous-phase energy. 相似文献
In order to non-destructively evaluate changes in toughness of cast duplex stainless steel, which is frequently used in main coolant pipes of PWR type nuclear power plants, due to thermal aging, we tried to apply thermoelectric power (TEP) measurement. because TEP is sensitive to microstructural material changes, and to clarify the mechanism behind TEP changes due to thermal aging. As a result, TEP of cast duplex stainless steel increased with aging time, and good correlations were found between TEP and toughness. Concerning the mechanism, TEP of high and low Cr content alloys was higher than that of intermediate Cr content alloys. Because high and low Cr areas are created in the ferrite phase due to thermal aging. TEP of the entire material increased. Furthermore, when each Cr fluctuating area acted in parallel, the increase in TEP became larger. According to the Mott-Jones theory, TEP is largely related to the electron density of states at the Fermi level. The electron density of states of Fe–Cr–Ni alloys in the valence band was measured with X-ray photoelectron spectroscopy (XPS). As a result, there was a high correlation between the TEP calculated from the XPS spectrum and the measured TEP. Therefore, we showed experimentally that the electron density of states changed due to variations in Cr concentration, which also affect TEP. 相似文献
Maximum stress intensity factors of a surface crack usually appear at the deepest point of the crack, or a certain point along
crack front near the free surface depending on the aspect ratio of the crack. However, generally it has been difficult to
obtain smooth distributions of stress intensity factors along the crack front accurately due to the effect of corner point
singularity. It is known that the stress singularity at a corner point where the front of 3 D cracks intersect free surface
is depend on Poisson's ratio and different from the one of ordinary crack. In this paper, a singular integral equation method
is applied to calculate the stress intensity factor along crack front of a 3-D semi-elliptical surface crack in a semi-infinite
body under mixed mode loading. The body force method is used to formulate the problem as a system of singular integral equations
with singularities of the form r−3 using the stress field induced by a force doublet in a semi-infinite body as fundamental solution. In the numerical calculation,
unknown body force densities are approximated by using fundamental density functions and polynomials. The results show that
the present method yields smooth variations of mixed modes stress intensity factors along the crack front accurately. Distributions
of stress intensity factors are indicated in tables and figures with varying the elliptical shape and Poisson's ratio. 相似文献
In order to deposit transparent and hard DLC films, magnetic field was introduced to enhance the plasma density of radiofrequency plasma chemical vapor deposition (RF-PCVD). In this paper, the configuration and computation of external magnetic field B are introduced. The restriction effect of magnetic field B on the charged particles and the effect of magnetic field B on the primary parameters-nonindependent power Pf and self-bias Uz were also studied. The mechanism of how magnetic field B affects self-bias Uz was analyzed. 相似文献