Mohsin Ganaie

Effect of laser irradiation on structural and optical properties of thermally evaporated thin films of amorphous Cd5Se95−xZnx

Thin films of Cd5Se95−xZnx (x = 0, 2, 4) were deposited by a thermal evaporation technique on glass substrates. These films were irradiated by pulsed laser at different durations of time. Laser irradiation of Cd5Se95−xZnx (x = 0, 2, 4) was accompanied structural changes which in turn leads to the change in optical properties of the material. The X-ray diffraction pattern of Cd5Se95−xZnx (x = 0, 2, 4) shows that the grain size increases due to the addition of Zn and decreases after laser irradiation. It was also found that the value of dislocation density increases after laser irradiation. The surface morphology of laser-irradiated thin films of Cd5Se95−xZnx (x = 0, 2, 4) shows that the disorderness or defects are produced due to laser irradiation. Energy dispersive X-ray spectroscopy confirms the elemental composition of the ternary alloy of Cd5Se95−xZnx (x = 0, 2, 4). The optical constants of Cd5Se95−xZnx (x = 0, 2, 4) were calculated from optical transmission spectra. The value of optical band gap increases after laser irradiation and decreases due to the addition of Zn.

Dc conductivity and High Field Behavior of Se 100-x Te x Alloy

The dc conductivity has been carried out in vacuum-evaporated thin films of amorphous Se100-xTex(x = 4, 8, 12, 16) in the temperature range of (317–378 K). It is found that dc conductivity increases and the activation energy (ΔE) decreases with increase of Te concentration. The conduction is explained on the basis of tunneling of carrier in the band tail of localized state. The high field measurement has been observed at various fixed temperature, a dc voltage (0–400 V) was applies across the sample. I–V characteristic data show that at low electric fields an ohmic behavior is observed. However, at high electric field super ohmic behavior is observed. Analysis of the data show the absence of space charge limited conduction (SCLC) in all glassy alloys as ln I/V versus V curves are not found to be straight lines. Instead ln I/V versus V 1/2 are found to be straight line, with high correlation coefficient. This suggests the conduction process is either of the Pool-Frenkel or Schottky emission. A detailed analysis show that dominant mechanism is Pool-Frenkel type conduction.

Study of Optical Parameters of the Thin Films of Se 100-x Hg x with Laser Irradiation

In this study the bulk samples of Se100-x Hgx (x = 0, 5, 15) have been prapered by conventional melt quenching technique. The thin films of the material were prepared by thermal evaporation technique. These thin films were irradiated with pulsed diode laser of wavelength 405 nm and power 100 mW for different durations of time. The transmission spectra was recorded by UV- visible spectrophotometer (200–1100 nm) before and after irradiation. The transmission spectra has been studied to measure the optical constants like extinction coefficient (k), absorption coefficient (α), optical band gap (Eg) and urbach’s energy (Ee). It has been found that the value of absorption coefficient and extinction coefficient increases after irradiation. Also the Urbach’s energy increases and the optical band gap decreases after irradiation. This indicates that the irradiation induces variety of defect states in the material system. It has also been found that the change of these optical parameters is more if the concentration of mercury is increased. This may be due to the addition of mercury and the bonding arrangement of the material system changes. These materials are found suitable for optoelectronic devices due to their high absorption coefficient.