The kinetics and initial stages of Bi 2 Te 3 electrodeposition on gold from an aqueous electrolyte composed of bismuth and telluryl ions and nitric acid were investigated using voltammetry and chronopotentiometry. For tellurium alone, it is found that the reduction of tellurium ions to tellurium occurs with four exchanging electrons at −0.05 V vs Ag/AgCl ͑3 M KCl͒. At −0.6 V, tellurium reduces to H 2 Te under kinetic control and the following simultaneous diffusion-controlled reaction occurs with one exchange electron per tellurium atom: HTeO 2 + + H 2 Te + H + + 2e − → 2Te + 2H 2 O. Bismuth telluride deposition starts at more positive potential than bismuth and tellurium deposit individually. It is suggested that the electrodeposition of Bi 2 Te 3 proceeds via a Stransky-Krastanov mechanism. From the Bard correction to the Sand equation, the diffusion coefficients of bismuth and telluryl ions were determined to be 1.90 ϫ 10 −5 and 1.39 ϫ 10 −6 cm 2 /s, respectively, in the investigated solutions. Due to the low diffusivity and solubility of telluryl ions, the limiting current density for Bi 2 Te 3 deposition in the investigated solution is low; it is only 2 mA/cm 2 . Above the limiting current density, a smooth deposit cannot be obtained without agitation. A smooth deposit can be achieved when the depletion of anions is eliminated.

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We report on selective area growth of InAs and GaAs quantum dots (QDs) on GaAs through ∼20 nm SiO2 windows prepared by block copolymer lithography. We discuss the mechanisms of growth through these masks, highlighting the variation of the resulting morphology (dot size, spacing, uniformity, and areal density) as a function of growth parameters. We have obtained highly uniform arrays of InAs and GaAs QDs with mean diameters and areal densities of 20.6 nm and 1×1011 cm−2, respectively. We have also investigated the optical characteristics of these QDs as a function of temperature and drawn correlations between the optical response and their crystalline quality.

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We report on selective area growth of InAs quantum dots on GaAs substrates patterned with a hexagonal array of 20 nm pores using block copolymer lithography. We discuss the mechanisms of growth, highlighting the variation in the resulting morphology as a function of nucleation enhancing AlGaAs layers. We also evaluate the optoelectronic performance of p-i-n photodiodes based on single layer nanopatterned grown InAs quantum dot devices. At low to moderate reverse biases, we observe room temperature photoresponse in both near- and mid-IR regimes. At high biases, we observe strong avalanche effects in the mid-IR range with a gain factor of ∼4000.