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.
The growth of CdS 0.08 Se 0.92 nanoparticles in glass is studied through the analysis of optical absorption spectra with the help of a quantized-state effectivemass model in which the conduction band effective mass is particle size dependent. The glass includes nanoparticles with an initial average size of ∼1.4 nm on cooling down to room temperature from the melt at ∼1000 • C. Particles grow by diffusion of the reactants onto the surface of initially formed nuclei upon heat treatment between 575 and 675 • C. Combined use of Arrhenius plots and the model yields an activation energy of ∼500 kJ mol −1 .
Growth of CdTe nanoparticles in glass is studied through the analysis of optical absorption spectroscopy with the help of a quantized state effective mass model. Glass includes nanoparticles with an initial size of ~1.6 nm on cooling to room temperature from the melt at ~1000 °C. Particles form by heterogeneous nucleation followed by diffusion-limited growth. The narrowest particle size dispersion of 15% is obtained for an average radius of ~2.28 nm at the end of heat treatment at 600 °C for 4.5 h. The magnitude of the absorption related to the number of particles is low due to the oxidation of Te. A combinative use of Arrhenius plots and the model yields an activation energy for diffusion of ~170 kJ mol -1 .
Physical vapor deposition (PVD) is used to grow CdTe thin films of different thicknesses on glass substrates. The characterization of the samples is then investigated optically and structurally. Three experimental techniques were used in this study; optical absorption (ABS), Raman, and X‐ray diffraction (XRD) spectroscopies. In optical ABS spectroscopy, the Urbach energy related to the width of long‐wavelength tail decreases from 827 to 585 meV as the thickness increases from 100 to 500 nm, respectively. The thickness‐dependent particle size was calculated using the value of the size‐dependent optical absorption edge energy. A shift of 710 meV in the ABS edge energy takes place as the thickness increases from 100 to 500 nm. Thickness‐dependent shifting and widening of XRD line is presumably due to the size effect and strain. Relative to the phonon frequency of bulk CdTe crystal, a thickness‐dependent blueshift was observed in Raman spectra for the Longitudinal Optical (LO) phonon frequency, while a redshift for the longitudinal acoustic (LA) and transverse optical (TO) phonon frequencies is observed. In the present work, the results of optical absorption, XRD, and Raman analyses are combined in order to study the effect of particle‐size evolution, thickness‐dependent strain, and structural disorder.
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