Environmental considerations in the MOVPE growth of (Hg,Cd)Te

Two solid-state colorimetric sensors for the precursors (Me2Cd, (Pr2Te)-Te-i, Hg) and the by-product dimethylmercury (Me2Hg) produced in the growth of mercury cadmium telluride by metal organic vapour phase epitaxy are described. KMnO4 adsorbed onto silica gel exhibits a colour change from pale purple to brown in a non-reductive carrier gas at Me2Cd, (Pr2Te)-Te-i, Hg, and Me2Hg gas-phase concentrations of 8, 3, 69 and 13 ppm, respectively. Niobium pentachloride, which can also be used in a hydrogen atmosphere, is found to change its colour from yellow to orange in the presence of gaseous Me2Hg, or to black with Me2Cd or (Pr2Te)-Te-i at concentrations of 26, 23 and 8 ppm, respectively. Water used for rinsing reactor glassware that has been washed with acid post-deposition can contain 0.3 g dm(-3) of mercury salts. This has been purified by the use of a column of ion-exchange resin. A colorimetric sensor for determining when the ion-exchange resin is saturated is described. Alcoholic solutions of 1,5-diphenylcarbazone are shown to be capable of detecting Hg2+ ions in water samples yielding a colour change from orange to purple at concentrations >7 ppm. (C) 2004 Elsevier B.V. All rights reserved.