Transferring porous layer from InP wafer based on the disturbance
We present a new method to transfer the three dimensional (3D) porous layer from InP wafer based on the disturbance, during electrochemical etching of n-InP (100) with chronopotentiometry with current ramp in 3 mol-L−1 NaCl solution. The potential bursting phenomenon was observed due to the disturbing instantaneously. In addition, the correlation between the amplitude of the potential and the porous layers separated from the InP wafer was discussed.
Morphology and strongly enhanced photoluminescence of porous GaAs layers made by anodic etching
Abstract Porous GaAs layers obtained by electrochemical etching were investigated using SEM, TEM and optical methods. The morphology, chemical composition and photoluminescence of porous layers were investigated. It was shown that porous layer consists of Ga 2 O 3 , As 2 O 3 , As 2 O 5 and GaAs submicron grains. Photoluminescence spectra of investigated porous layers consist of “infrared” and “green” spectral structures. The observed short wavelength photoluminescence (PL) at 590–778 nm of the porous layer is explained by the quantum size effect in the GaAs nanocrystals.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME