Determination of X6 valley hot electron dynamics and the intervalley X6 → Γ6 scattering time in GaAs

The time-resolved infrared absorption in a GaAs crystal was measured by picosecond visible-pump and infrared-probe absorption spectroscopy. The dynamics of hot electrons in the X₆ valley subsequent to the excitation was obtained. From the time evolution of the population of the X₆ electrons, the intervalley X₆ → Γ₆ scattering time was determined to be ≈ 500 fs by a rate equation analysis.     

An improved numerical method for computation of stress intensity factors along 3D curved non-planar cracks in FGMs

A simplified strategy based on the interaction energy integral is implemented in the finite element framework to evaluate mixed mode Stress Intensity Factors (SIFs) in 3D non-planar cracks. The proposed approach does not require any a priori information about crack front and crack surface curvatures, therefore different arbitrary non-planar cracks can be easily investigated. In particular, both conical and lens-shaped cracks in homogeneous materials are considered as case studies in order to demonstrate the accuracy of the present approach. Finally, the computational strategy is extended to Functionally Graded Materials (FGMs) and the effect of graded material properties (Young’s modulus and Poisson’s ratio) on the SIFs is studied in detail.