Structural and Optical Properties of CdBr Films Deposited On to Ge Substrates رسالة ماجستير

Abstract

Structural and Optical Properties of CAdBr: Films Deposited On to Ge Substrates In this thesis cadmium bromide (CdBr) thin are coated onto glass and amorphous germanium (Ge) thin film substrates. The constructed Ge/CdBr bilayers are structurally and optically characterized. The X-ray diffraction analysis have shown that the Ge, CdBr: and Ge/CdBr, films, which are grown by the thermal evaporation techniques, are of amorphous and polycrystalline structures, respectively. Coating CdBr: onto Ge caused a decrcasc in crystallite size a companied with an increase in the lattice parameters, microstrain, stacking faults and defcct density. Optically, remarkable redshift in the transmittance and reflectance spectra is observed upon coating CdBr, onto Ge, which is considered as a substrate for CdBr. The light absorbability in the visible and infrared ranges of light increased by more than 80 times allowing large scale of light absorption. It is also noted that the energy band gap is redshifted from 3.32 to 3.27 eV as a result of depositing CdBr on to glass by amorphous Ge substrates. On the other hand, the dielectric spectra of Ge/CdBr mostly followed that of Ge meaning that the dielectric constant values have increased significantly. In addition,

employing Drude — Lorentz model to determine the optical conductivity parameters have shown that the drift mobility and plasmon frequency of CdBr: can be increased when deposited on to glass by Ge. The plasmon frequency remarkably incrcased reaching values of 12 GHz making the Ge/CdBr, interfaces promising for application in communication technology.