کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1611119 | 1516289 | 2014 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Structural and optical characterization of CdTe quantum dots thin films
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی مواد
فلزات و آلیاژها
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Structural and optical characterization of CdTe quantum dots thin films Structural and optical characterization of CdTe quantum dots thin films](/preview/png/1611119.png)
چکیده انگلیسی
Cadmium telluride quantum dots (CdTe QDs) have been synthesized using hot-injection chemical technique. The CdTe QDs thin films were deposited onto optical flat fused quartz substrates using thermal evaporation technique. The CdTe QDs powder and the as deposited films were characterized using X-ray diffraction and high resolution transmission electron microscope (HRTEM). The X-ray analysis shows that both CdTe QDs powder and the as deposited films crystallize in cubic zinc-blende type structure with lattice parameter 6.46Â Ã
and 6.45Â Ã
, respectively. The X-ray calculation shows that the average crystallite size of the as deposited CdTe QDs films varied from 1.1 nm for the powder to 2.3 nm for the thin film. The HRTEM examination of the as deposited films shows that the average particle size vary from 2.5 nm for the powder to 2.7 nm for the thin film. For the as deposited films, the dependence of (αhν)2 on the incident photon energy indicates that the optical transitions within the film are allowed direct with energies observed at Eg1â
2eV and Eg2â
2.3eV which attributed to quantum confinement effect. The optical band gap increases from 1.5 eV for microstructure CdTe to 2 eV for nanostructure quantum dots which corresponding to wavelength(620 nm) so it is a great benefit to use CdTe quantum dots as solar harvesting devices application in solar spectrum region (400-800 nm). Urbach energy is calculated and found to be 360 meV which is higher than microstructure CdTe. The refractive index and refractive index dispersion of the as deposited CdTe QDs film has been calculated from transmission and reflection spectra. It has been found that the refractive index is reduced from (2.66) for microstructure CdTe to be (1.7) for CdTe quantum dots. The variation of the refractive index at normal dispersion is well described by Wemple-DiDomenico single oscillator model. The dielectric constant at infinite frequency εâ and the ratio of free carriers' concentration to the effective mass (N/mâ) are calculated and discussed. Finally, the non linear optical parameters are calculated using some empirical relation.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Alloys and Compounds - Volume 604, 15 August 2014, Pages 253-259
Journal: Journal of Alloys and Compounds - Volume 604, 15 August 2014, Pages 253-259
نویسندگان
M.M. El-Nahass, G.M. Youssef, Sohaila Z. Noby,