Measurements were made on the title system using an e.m.f. cell, without liquid junction, of the type : Pt, H2(g, 1 atm)lHBr(ml), (B~)~NBr(rn~)lAgBr, Ag at 25°C in the total molality ranges of m, where m = ml +ma, equal to 0.1, 0.25, 0.5 and 1.0 mol kg-l. Harned's Rule has been tested for the variation of the activity coefficients in these mixtures of electrolytes. The results are discussed at low dilution (0.1 rnol kg-') in terms of the specific interaction coefficient, B ( B " ) ~N + , B ~-, as well as interpreted in terms of Pitzer's equation for the total molality range under investigation.Increasing use of the activity coefficients of mixtures of strong electrolytes in such fields as chemical oceanography, metallurgical chemistry and studies on blood plasma has recently prompted numerous This paper reports part of a study into the aqueous behaviour of a series of tetra-alkyl groups substituted into the ammonium cation (NHZ). The purpose of the present investigation is two-fold : (a) to study salt effects in mixtures of hydrobromic acid and tetrabutylammonium bromide, and (b) to determine if there is any regular sequence in the strength of H+-(Bu)~N+, (Bu),N+ -Br-, or (Bu)~N+ -Br--H+ interactions when ammonium bromide is replaced by the tetrabutylammonium ion. To obtain the necessary activity coefficient data, e.m.f. measurements were made at 25°C using cells of the type
With the objective of developing an improved process for in situ etching of GaAs-based materials in organometallic vapor phase epitaxy reactors, GaAs wafers and AlxGa1−xAs epilayers have been etched with CH3I vapor in a horizontal reactor operated at atmospheric pressure with H2 or He carrier gas. For a H2 flow rate of 2.1 s lpm, etching temperatures from 400 to 625 °C, and CH3I mol fractions (yCH3I)from 0.0012 to 0.015, the measured GaAs etch rate r (in Å min−1) is given by r = k0 y0.83CH3I exp[ − 45(kcal mol−1)/RT] with k0=3.2×1016 Å min−1. The value of k0 depends on the type of carrier gas, flow rate, total pressure, and reactor geometry. The etch rate appears to be controlled mainly by the decomposition of CH3I to CH3 and I, for which the activation energy has been reported to be 43.5 kcal mol−1. The etch rate of AlxGa1−xAs epilayers with x up to 0.7, which was measured at 480 °C with yCH3I= 0.015, does not depend on Al content. The surface morphology of etched GaAs wafers improves with decreasing temperature. Specular surfaces are maintained at temperatures below 500 °C for etch depths up to 5000 Å.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.