Cl2 Ion Research Articles

Investigation of electrochemical etch differences in AlGaAs heterostructures using Cl2 ion beam assisted etching

A deeply etched, anisotropic 45° and 90° mirror technology is developed for AlxGa1−xAs heterostructures using a Cl2 ion beam assisted etching system. When etching vertically, using a conductive low-erosion Ni mask, electrochemical etch differences between layers with various Al mole fractions caused nonuniform sidewall profiles not seen in semi-insulating GaAs test samples. These variations, based on alloy composition, were found to be negligible when etching at a 45°. A Si3N4-Ni etch mask is designed in order to electrically isolate charge buildup caused by the incoming Ar+ ion beam to the Ni layer, preventing conduction to the underlying epitaxial layers. This modification produced smoothly etched facets, up to 8 μm in depth, enabling fabrication of substrate–surface-emitting slab-coupled optical waveguide lasers and other optoelectronic devices.

Hydrogen permeation and corrosion behaviour of high strength steel 35CrMo under cyclic wet–dry conditions

Hydrogen permeation behaviours of high strength steel 35CrMo under different cyclic wet–dry conditions have been investigated by using Devanathan–Stachurski's technique. Four electrolytes were used: distilled water, seawater, seawater containing 1500 ppm H2 S and seawater containing 0 · 03 mol L2 1 SO2. The corrosion weight loss of 35CrMo in the wet–dry cycles was measured simultaneously. The experimental results show that hydrogen can be detected at the surface opposite to the corroding side of the specimen during wet–dry cycles and the permeation current density during a wet–dry cycle showed a maximum during the drying process. The hydrogen permeation was obviously promoted by Cl2 ions, H2 S and SO2. The hydrogen permeation in the real marine atmosphere has also been investigated. There is a clear correlation between the amount of hydrogen permeated and the corrosion weight losses. Results show the importance of hydrogen permeation that merits further investigation.

Reactive ion etching of Si by Cl and Cl2 ions: Molecular dynamics simulations with comparisons to experiment

We present results of molecular dynamics simulations of reactive ion etching (RIE) of a reconstructed Si(100)(2×1) surface. The existing Stillinger–Weber interatomic potential for Si/Cl of Feil et al. has been modified by correcting the Si–Si bond strength for a SiCln moiety bound to a Si surface and the Si–Cl bond strength in SiClm molecules. This potential has been used to study RIE of Si by Cl and Cl2 ions. The calculated properties such as the Si yield, product stoichiometry, stoichiometry of the chlorosilyl surface, and Cl content of the chlorosilyl layer are in reasonable agreement with experiment. The dissociative chemisorption probability of Cl2 on Si(100)(2×1) as a function of energy has been simulated and the results are in reasonable agreement with experiment.

Surface composition and etching of III-V semiconductors in Cl2 ion beams

Surface composition and etching of InP and GaAs in Cl2 ion beams was investigated. In situ analysis of the substrate using Auger electron spectroscopy demonstrated selective removal of phosphorous from InP leaving a thin (⩽50 Å) surface layer enriched with In after etching at room temperature with a 500-eV Cl+/Cl+2 beam. GaAs does not show selective removal of the group V element, resulting in no significant change in surface composition after etching. These results reflect the involatility of the In chlorides at room temperature. Etch rate results indicate that at low ion energy (200 eV) or high neutral reactant flux, removal of the group III chloride from the surface is rate limiting. At high ion energy (500 eV) and low neutral flux, supply of reactant to the surface is rate limiting.

Chlorine randomization between phenyl groups in the electron impact-induced fragmentation of polychlorinated biphenyls

The mass spectra of dichlorobiphenyls show chlorine randomization over both phenyl rings with the exception of 2,2′- and 2,6-biphenyl (I, e and f) in which both chlorine atoms are ortho to the Ph–Ph bond; similar results are obtained with tetrachlorobiphenyls which show chlorine randomization in the M– Cl2 ion.