Growth of cdte nanocrystals in glass via heat-treatment procedure and investigation of electronic, linear and nonlinear optical properties of these nanocrystals

Cadmium-telluride (CdTe) from the II-VI group semiconductors class occupies a very important place in the present-day semiconductor technology. The technological importance of the cadmium-telluride arises from its being a cost-efficient,pass-through semiconductor that has the optimum direct forbidden energy band gap to benefit from the electromagnetic radiation energy of the sun, which reaches our world, and the highest linear electro-optic coefficient in its own group.In this study, the electronic and optical features of cadmium telluride crystals in very small dimensions such as just a few nanometers have been handled closely and systematically. The cadmium-telluride nanocrystals have been tried to grow by applying the melting and two step heat treatment process to small samples cutting from the commercially-available,RG850-coded Schott filter glass. The dimensions, distributions, numbers, and the compositions of the crystals grown in the glass samples have been examined depending upon the conditions of the heat treatment (temperature, time, and environment).These parameters of the nanocrystals have been determined as based on the results of optical absorption and resonant Raman measurements. In consequence of the said measurements, it has been understood that average radius of the nanocrystals grown in the glass environment in the open air atmosphere in the samples vary between ~ 3-5 nm, that they have almost narrow distribution and could not be grown as pure cadmium-telluride actually, and that there is zinc in their compositions. The radiation capability of these impure cadmium-telluride nanocrystals in the visible region has been examined through photoluminescence measurements, and their nonlinear optical features such as the absorption and refraction index changes through photomodulation measurements. The temperature dependence of the forbidden energy band gaps, another important parameter for the semiconductor nanocrystals, has been examined by the aid of optical absorption measurements performed in room and above temperatures for the impure cadmium-telluride nanocrystals.