Two different mechanisms of formation of quantum dots in borosilicate glass

Abstract

The nucleation and growth of Cd1-xZnxS and CdSxSe1-x nanocrystals in borosilicate glass are investigated through optical absorption and resonant Raman scattering measurements. The optical absorption spectra are interpreted with the help of a quantized-state effective-mass model applied for heterogeneous and homogeneous nucleation of nanocrystals. Stoichiometry changes of the particles during the growth stage are monitored by resonant Raman measurements. The findings indicate that the formation of Cd1-xZnxS particles involves a stage of homogeneous nucleation and then a rapid transition to ripening. No growth is observed. CdSxSe1-x particles undergo heterogeneous nucleation and growth simultaneously with a gradual transition into the ripening stage.

Solid‐phase precipitation of CdTe nanoparticles in glass

“…The evolution of the absorption edge spectra over time is consistent with heterogeneous nucleation of nanoparticles, followed by diffusive growth. The time rate at which the absorption peak position moves to lower energies, i.e., = / E t~0.25 eV h -1 at 625 °C compares well with the previously reported rate of ~0.33 eV h -1 at 625 °C for the growth of CdS 0.5 Se 0.5 particles [9] and ~0.41 eV h -1 at 625 °C for the growth of CdS 0.08 Se 0.92 particles [10] in glass, which undergo heterogeneous nucleation. In diffusionlimited growth of the particles, all nuclei are assumed to be extrinsic and created at t = 0 prior to the heat treatment during quenching the melt to room temperature.…”

“…A Gaussian weighting function was used to include the inhomogeneous broadening for the size distribution. The details of the model calculation have been published elsewhere [9,23]. Our purpose here is not to test the theory rather to account for the observed evolution of the absorption peaks with time by a simple effective mass based model in which the height of potential barrier is infinite.…”

“…The present work follows previous work in Cd 1-x Zn x S and CdS x Se 1-x by Yükselici [9,10]. We employed optical absorption spectroscopy to study the growth kinetics of CdTe nanoparticles in glass.…”

Thermal treatment-dependent chemical composition of ternary CdS1−xSex nanocrystals grown in borosilicate glass

“…Diffusion-limited growth in a glass matrix is a well elaborated technique for obtaining II-VI semiconductor nanocrystals, with the growth process basically consisting of three stagesnucleation, normal growth, and coalescence (Ostwald ripening or competitive growth) [1][2][3][4][5][6][7][8]. The near-spherical shape of thus grown nanocrystals is evidenced by transmission electron microscopy (TEM) [1][2][3]9].…”

Phonon spectra of quaternary Cd1–yZny S1–xSex semiconductor nanocrystals grown in a glass matrix

“…In any case, for relatively small y, in both cases (Cd 1-y Zn y S and Cd 1-y Zn y Se), the compositional shift of the LO phonon frequencies is monotonous, the zinc-induced increment being given by Similarly to [13], the Se content for the NC series was determined from the LO phonon peak frequency difference Δν for the sample subjected to the least intense heat treatment. As follows from [23], for CdS 1-x Se x NCs x = 0.0165Δν -0.94 (Δν being taken in cm -1 ).…”