5507
Nahed Hamada Ibrahem Teleb
Structural Characterization And Physical Properties Of Ternary Se75Te25-Xgex Thin Films
Selenium Tellurium Germanium (se-Te,Ge-Se,Ge-Te,Te-Te), Pulsed laser deposition(PLD), X-Ray Diffraction (XRD); Scanning Electron Microscopy (SEM); Transmission Electron Microscopy (TEM); Differential scanning caliometry (DSC); Optical properties; Electrical Properties.
Se75Te25-xGex(0 ≤ x ≤ 8) bulk materials was firstly prepared from the constituent elements in the stoishiometric proportions in evacuated silica tubes using laser deposition technique the prepared bulk ingot materials were characterized by means of X-ray differaction, [XRD] depicts the absence of any sharp diffraction peaks within the investigated“2θ” range, which confirms the expected amorphous nature of the prepared powdery compositions. Pulsed laser deposition technique was used for preparation of Se75Te25-xGex(0 ≤ x ≤ 8) thin films. high power femto-second laser [Titanium Sapphire] ~ Coherent US ~ with a wavelength of 800 nm and pulse duration of 30 fs delivered an average power of 700 m watt. The laser was operated at 1000 Hz and focused through a 50 cm focal length lens onto a rotating target at a 45° angle of incidence. The energy dispersive X-ray spectrometry [EDX], X-ray diffraction, transmission electron microscopy, electron diffraction, scanning electron microscopy and spectrometer were used to investigate the prepared films. Coordination number, mean bond energy, and heat of atomization for the ternary Se75Te25-xGex system was calculated. The optical properties of the deposited Se75Te25-xGex thin films were calculated in the wavelength range 500-2500 nm. The single-effective oscillator model proposed by the Wemple–DiDomenico (WDD) used to analyze the refractive index dispersion of the investigated compounds. Also the dielectric constant, absorption coefficient and optical band gap of the compounds were analyzed. The effect of thermal annealing on the optical properties of the deposited Se75Te25xGex(0 ≤ x ≤ 8) thin films was carried out at 150 °C. The DC electrical conductivity of the deposited films was studied. The measurement has been carried out during both heating and cooling cycles in the temperature range 300-530 K, the magnitude of the film conductivity increases with increasing Ge content at%. Also the activation energy, ∆Eσ induced. The current-voltage characteristic curves was reproducible nonlinear behavior in both forward and reverse directions; indicates that the prevalent conduction mechanism is non-ohmic in nature.
2017
Ph.d
Ain Shams
Faculty of Girls for Art Science