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TEM and Raman scattering determination of nanocrystalline distributions of CdSxSe1-x nanoparticles embedded in glass matrix

The extraction of structural parameters of nanocrystalline materials prepared under different conditions is a necessary prerequisite in understanding their properties and possible application in technology. Therefore, their structural features are a widespread subject of research nowadays. However, there are special types of nanocrystalline materials, where the extraction of their structural parameters using conventional diffraction techniques like XRD fails. They are very often thin films, embedded nanosized crystals in glass host, or implanted ions in matrix. In such cases, the selected area electron diffraction (SAED) is the only tool in structural characterization [1]. Here, we present the investigation of commercially available Schott filter glasses with different concentration of CdSxSe1-x quantum dots having different sizes, embedded in a glass host. The samples OG515, OG530, OG550, OG570, OG590, were investigated by transmission electron microscopy and SAED (JEOL 2010 200kV microscope with point resolution 0.19 nm). The numbers next to the letters point out the cut-off wavelength of the glass. The grains of CdSxSe1-x are crystallized in the hexagonal structure of wurtzite type, space group P63mc. The analysis of corresponding SAED pattern (Figure 1(c)), using the formula for hexagonal structure, leads to the lattice parameter values of CdSxSe1-x, a=0.4196 nm and c=0.6857nm.The TEM micrographs indicate the presence of nanocrystallites in the glass matrix, whose sizes are from 2.6 nm (OG515) to 6.7 nm (OG590). The grains are mostly spherical in shape. The size distribution of TiO2 [2] and CdSxSe1-x nanocrystallites obtained by TEM showed a good agreement with the Raman scattering results [3]. In Fig 2, we give the distributions for CdSxSe1-x nanoparticles in an amorphous host A. We used Fourier filtering of HRTEM image (Fig 1(a)) in order to reveal lattice fringes (110) and (102) of CdSxSe1-x, nanocrystallites.

Nanoparticles; TEM; Raman Scattering

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