The Urbach tail in crystalline GaAs and Si due to thermal vibration is evaluated in the temperature range 0—810 K. Recent experiments suggest that there is no thermally induced Urbach tail in undoped GaAs. This is most unexpected since thermally induced tails at the absorption edge having the Urbach form and widths Eo(T) linear in T are observed in a wide range of crystalline and amorphous semi...

Investigation of new calculate depends on the controlled optical properties of nanomaterials. Understanding the growth mechanism and growth parameters of nanostructured materials is essential. ZnO is one of the most important semiconductor materials for its semiconducting characteristics. In the present paper, we investigated a new model by theoretical methods; it is based on correlation from t...

We report a study of the 2.8 eV blue luminescence ~BL! in heavily Mg-doped p-GaN via resonant excitation with a tunable blue dye laser. The dependence of the BL on the excitation photon energy (Eex) is unlike that of the yellow luminescence found in n-type GaN. An Urbach-type band tail, with Urbach parameter of 33 meV is observed in the vicinity of the BL energy. We propose that the peak energy...

We study a specific type of lifetime broadening resulting in the well-known exponential "Urbach tail" density of states within the energy gap of an insulator. After establishing the frequency and temperature dependence of the Urbach edge in GaAs quantum wells, we show that the broadening due to the zero-point optical phonons is the fundamental limit to the Urbach slope in high-quality samples. ...

zno and zno:mn nanocrystals synthesized via reverse micelle method. the size, band gap, urbach energy, optical constants and penetration depth of nanocrystals were calculated by uv-vis spectroscopy data. the surface morphology was studied with the use of scanning electron microscope (sem). moreover the samples exposed to gama ray source of 60co and their thermoluminescence properties were also ...

This article discusses details study on crystallization , optical properties of Li-Al-Si-La glass containing nanocrystalline LaF3.and their optical energy gaps. The Urbach energy of glass samples was evaluated. By using (2% mole) Tb the green–blue range emission occurred, while by accumulation 1% mole Gd beside Tb, the indigo emission intensity (418 to 441 nm) increased.

Borosilicate BK7 glasses doped with different amounts of CeO2 (0.5,1,1.5%) were prepared by the convenient melting process in this work. DTA analysis proved that 0.5-1% CeO2 has a network modifier role and then up to 1.5% it shows network former role.For structural studies, FT-IR and Raman spectroscopy were carried out. Fermi energy level, direct/ indirect optical band gap and Urbach energy wer...

Thin films of GeTe2 were deposited on glass substrates using radio-frequency magnetron sputtering with various hydrogen flow rates in the growth chamber. Transmission data of deposited films were taken and used to determine optical constants refractive index n , extinction coefficient , and absorption coefficient and the energies corresponding to absorption coefficients of 104 and 103 cm−1 E04,...

ZnO and ZnO:Mn nanocrystals synthesized via reverse micelle method. The size, band gap, Urbach energy, optical constants and penetration depth of nanocrystals were calculated by UV-vis spectroscopy data. The surface morphology was studied with the use of scanning electron microscope (SEM). Moreover the samples exposed to Gama ray source of 60Co and their thermoluminescence properties...