Studies on the Electrochemical Deposition of III -v Materials from Non-Aqueous Electrolytes
The electrochemistry of acetonitrile solutions of indium(III) tribromide and arsenic(III) tribromide was studied. Several supporting electrolytes were investigated with the aim of identifying suitable ones for the electro -deposition of each element. Results point to adsorption taking part in the mechanism of indium(III) reduction in the presence of bromide ions. That phenomenon significantly increased the kinetics of the process, In the case of arsenic(III), its reduction was found not to be as sensitive to bromide -ions' presence, while the kinetics of arsenic oxidation were markedly increased. Electrodeposition of composite thin films containing indium and arsenic was achieved from an electrolyte consisting of 0.1 M (N(n-butyl)_4) ClO _4 plus 1-6 mM InBr_3 and AsBr_3. Electrodeposition was carried out at room temperature, on copper and n-type indium phosphide electrodes. Characterization of the resulting electrodeposits by X-ray diffraction revealed that they are composed mainly of indium and arsenic in their elemental states. Arsenic was determined to exist in the alpha -crystalline form, though the presence of additional arsenic in other amorphous states was not ruled out. The films also contain a small mole fraction of indium arsenide. The oxides of these elements were also detected on the surface of the deposits, and are likely the result of exposure of the deposits to the atmosphere during handling. The observed microstructure of the composite films, namely heterogeneous indium and arsenic micro-domains, as opposed to an intimately-mixed deposit, was explained as being due to poor wetting of indium on arsenic. Indium was found to deposit mostly as nodule-like structures on copper and on indium phosphide substrates, while arsenic deposited mostly as a relatively-smooth, adherent, polycrystalline film on all substrates. Electrodeposits were annealed at 300^circC under nitrogen but no significant chemical transformations were detected in them. The elemental composition of the deposits could be made to fall in the range of (In/As) = 1 to 2 by electro -deposition at constant potential between ^ -2.0 to ^-2.2 V vs. polyvinylferrocene/ferricinium(on Pt) reference electrode.
- Pub Date:
- GROUP III V;
- INDIUM ARSENIDE;
- Chemistry: Physical; Chemistry: Inorganic; Engineering: Materials Science; Physics: Condensed Matter