Effects of annealing on electrical and optical properties of a multilayer InAs/GaAs quantum dots system

Abstract

A systematic investigation of the properties of the InAs/GaAs self-assembled quantum dots (SAQDs) system subjected to a post-growth annealing using capacitance-voltage, Raman scattering and photoluminescence measurements is presented. The application of both electrical and optical methods allowed us to obtain reliable information on the microscopic structural evolution of this system. The single layer and the multilayer quantum dots were found to respond differently to the annealing process, due to the differences in strain that occur in both systems. The diffusion activated by strain provoked the appearance of an InGaAs alloy layer in substitution to the quantum dots layers; this change occurred at the annealing temperature T = 600 °C in the multilayer system. A single dot layer, however, was observed even after the annealing at T = 700 °C. Moreover, the low temperature annealing was found to improve the homogeneity of the multilayer system and to decrease the electrical interlayer coupling.

An approach toward miRNA detectionviadifferent thermo-responsive aggregation/disaggregation of CdTe quantum dots

“…But aer addition of miR-155 and duplex formation with DNA probe, the interaction between chalcogenide QDs and DNA/miRNA heteroduplex [21][22][23][24][25][26][27] results in aggregation of the QD nanoparticles and their UV-vis absorption coefficient is reduced and therefore, their uorescence intensity also is reduced ("signal off") [28][29][30][31][32] (Scheme 3a 0 ). Then, by applying melting temperature, DNA probe strand dissociated from miRNA and red emission (at 615 nm) can be observed ("signal on") [32][33][34][35][36] (Scheme 3b 0 ). This is due to the shorter distances between the CdTe QDs in the dsDNA/miRNA than that of the ssDNA and free CdTe QDs, which can increase the dipole-dipole interaction between the CdTe QDs resulting in a larger Stoke's shi emission change.…”

“…Here, this nucleic acid heteroduplex aggregates thioglycolic acid (TGA)-stabilized CdTe QDs; and as a result, uorescence quenching occurs. [28][29][30][31][32] Applying melting temperature (T m : is dened as the temperature at which half of the double strand begins to dissociate), resulted in a larger Stoke's shi emission change upon the de-aggregation, [32][33][34][35][36] which depends on the concentration of miRNA. This is due to the shorter distances between the CdTe QDs in the heteroduplex than that of the single strand and free CdTe QDs, which can increase the dipole-dipole interaction between the CdTe QDs, resulting in a larger Stoke's shi emission change (Schemes 1-3).…”