Shabir Ahmad

Investigation of structural and optical properties of 100 MeV F7+ion irradiated Ga10Se90-xAlxthin films

Present work focuses on the effect of swift heavy ion (SHI) irradiation of 100 MeV F7+ ions by varying the fluencies in the range of 1 × 1012 to 1 × 1013 ions/cm2 on the morphological, structural and optical properties of polycrystalline thin films of Ga10Se90-xAlx (x = 0, 5). Thin films of ~300 nm thickness were deposited on cleaned Al2O3 substrates by thermal evaporation technique. X-ray diffraction pattern of investigated thin films shows the crystallite growth occurs in hexagonal phase structure for Ga10Se90 and tetragonal phase structure for Ga10Se85Al5. The further structural analysis carried out by Raman spectroscopy and scanning electron microscopy verifies the defects or disorder of the investigated material increases after SHI irradiation. The optical parameters absorption coefficient (α), extinction coefficient (K), optical band gap (Eg) and Urbach’s energy (EU) are determined from optical absorption spectra data measured from spectrophotometry in the wavelength range 200–1100 nm. It was found that the values of absorption coefficient and extinction coefficient increase while the value of optical band gap decreases with the increase in ion fluence. This post irradiation change in the optical parameters was interpreted in terms of bond distribution model.

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.

Structural and optical analysis of 60Co gamma-irradiated thin films of polycrystalline Ga10Se85Sn5

The present study focuses on the effects of gamma irradiation on structural and optical properties of polycrystalline Ga10Se85Sn5 thin films with a thickness of ∼300 nm deposited by the thermal evaporation technique on cleaned glass substrates. X-ray diffraction patterns of the investigated thin films show that crystallite growth occurs in the orthorhombic phase structure. The surface study carried out by using the scanning electron microscope (SEM) confirms that the grain size increases with gamma irradiation. The optical parameters were estimated from optical transmission spectra data measured from a UV–vis-spectrophotometer in the wavelength range of 200–1100 nm. The refractive index dispersion data of the investigated thin films follow the single oscillator model. The estimated values of static refractive index n0, oscillator strength Ed, zero frequency dielectric constant ε0, optical conductivity σoptical and the dissipation factor increases after irradiation, while the single oscillator energy Eo decreases after irradiation. It was found that the value of the optical band gap of the investigated thin films decreases and the corresponding absorption coefficient increases continuously with an increase in the dose of gamma irradiation. This post irradiation changes in the values of optical band gap and absorption coefficient were interpreted in terms of the bond distribution model.

Effect of60Co γ-irradiation on structural and optical properties of thin films of Ga10Se80Hg10

Thin films of Ga10Se80Hg10 have been deposited onto a chemically cleaned Al2O3 substrates by thermal evaporation technique under vacuum. The investigated thin films are irradiated by 60Co γ-rays in the dose range of 50–150 kGy. X-ray diffraction patterns of the investigated thin films confirm the preferred crystallite growth occurs in the tetragonal phase structure. It also shows, the average crystallite size increases after γ-exposure, which indicates the crystallinity of the material increases after γ-irradiation. These results were further supported by surface morphological analysis carried out by scanning electron microscope and atomic force microscope which also shows the crystallinity of the material increases with increasing the γ-irradiation dose. The optical transmission spectra of the thin films at normal incidence were investigated in the spectral range from 190 to 1100 nm. Using the transmission spectra, the optical constants like refractive index (n) and extinction coefficient (k) were calculated based on Swanepoel’s method. The optical band gap (Eg) was also estimated using Tauc’s extrapolation procedure. The optical analysis shows: the value of optical band gap of investigated thin films decreases and the corresponding absorption coefficient increases continuously with increasing dose of γ-irradiation.

Enhancement in the dielectrics of poly( o -toluidine)/single wall carbon nanotubes (POT/SWCNTS) polymer nanocomposites for electrical energy storage

Present study focuses on influence of carbon nanotubes in POT polymer, in order to improve performance of energy storage devices. (POT/SWCNTS) nanocomposites are synthesized by situ polymerization with different concentrations of SWCNTS. POT had long chain of qunoid and benzoined rings provide together large transport of charge along with SWNTs resulting to store large amount of electric charge. Synthesized samples are characterized by dc conductivity; UV–Vis studies, FTIR, X-ray diffraction (XRD) and dielectric techniques. Electrical conductivity enhances up to four orders with dopant concentrations. Incorporation of dopant into polymer matrix is confirmed by FTIR studies. XRD analysis revealed crystallinity of nanocomposites. Present consequences of synthesized polymer nanocomposites shows meaningful impact with changes in dielectric properties due to better dispersion of SWCNTS in polymer matrix. As results enhancements in dielectric parameters values, highlights their great potential for supercapacitors. These nanocomposites do not need any binding substance that is an important practical advantage.

Laser irradiation induced photo-crystallization in nano-structured amorphous Se90−xHgxS10 (x = 0, 5, 10, 15) thin films

The present study focuses on the influence of laser irradiation induced photo crystallization on the modification of the optical and electrical properties of thermally evaporated amorphous Se90−xHgxS10 (x = 0, 5, 10, 15) thin films. The chemical composition and amorphous nature of the as-prepared thin films were examined by energy dispersive X-ray analysis and X-ray diffraction (XRD) respectively. However, the XRD analysis revealed the crystalline nature of the thin films irradiated using a 337.1 nm pulsed laser. These results were further investigated by surface morphological techniques, namely atomic force microscopy (AFM) and scanning electron microscopy (SEM). An enhancement in the average grain sizes after laser irradiation was observed. The absorption spectra obtained using a UV-vis-spectrophotometer were evaluated using the Urbach’s edge method. As the duration of laser irradiation was increased, the optical energy gap and tail energy width for all the compositions decreased. Further, it has been observed that the value of the optical energy gap decreases with Hg content in the Se–S alloy. These results have been interpreted on the basis of laser irradiation-induced photo-crystallization in the film. Electrical analyses such as dark dc conductivity and photoconductivity in the temperature range 310–390 K show an enhancement of the electrical conductivity and a reduction in activation energy as the irradiation time increases and specify that the density of defect states decreases after irradiation. Temperature dependent photoconductivity measurements show similar trends to that of dark conductivity. This is because the photo-created carriers can move easily in laser irradiated thin films due to the crystallinity of the material.

Electronic excitation induced structural, optical and electrical properties of Se85S10Zn5 thin films and applicability of a single oscillator model

The effect of electronic excitation induced by 120 MeV Ag9+ ion irradiation on the structural, optical and electrical properties of Se85S10Zn5 thin films has been investigated at various ion fluencies. Thin films of Se85S10Zn5 have been prepared by vacuum evaporation technique with thickness ∼250 nm on cleaned glass substrates. X-ray diffraction (XRD) patterns confirm that preferred crystallite growth occurs in the (100) plane corresponding to the hexagonal phase structure. XRD analysis also shows that the crystallite size decreases with increasing ion fluence. This post irradiation change was also supported by morphological studies carried out by scanning electron microscopy (SEM) which indicate the grain fragmentation process has been taking place due to excessive energy deposition during the passage of ion beams. The optical parameters calculated from optical transmission spectra in the wavelength range 200–1000 nm show the reduction of the optical band gap and an enhancement in absorption coefficient after ion irradiation. The data from refractive index dispersions of the thin films before and after irradiation fit well with a single oscillator model. This post irradiation change in the values of optical parameters suggests that the investigated material may have industrial applications for various optoelectronic devices. Electrical properties such as dc conductivity of investigated thin films were carried out in the temperature range 309–370 K. Analysis shows that the value of the activation energy decreases with the increase of ion fluence indicating that the density of defect states increases after swift heavy ion irradiation.

Effect of 50MeV Li3+ ion irradiation on structural, optical and electrical properties of amorphous Se95Zn5 thin films

Present work focuses on the effect of swift heavy ion (SHI) irradiation of 50MeV Li3+ ions by varying the fluencies in the range of 1×1012 to 5×1013 ions/cm2 on the morphological, structural, optical and electrical properties of amorphous Se95Zn5 thin films. Thin films of ~250nm thickness were deposited on cleaned glass substrates by thermal evaporation technique. X-ray diffraction (XRD) analysis shows the pristine thin film of Se95Zn5 growsin hexagonal phase structure. Also it was found that the small peak observed in XRD spectra vanishes after SHI irradiation indicates the defects of the material increases. The optical parameters: absorption coefficient (α), extinction coefficient (K), refractive index (n) optical band gap (Eg) and Urbach’s energy (EU) are determined from optical absorption spectra data measured from spectrophotometry in the wavelength range 200-1000nm. It was found that the values of absorption coefficient, refractive index and extinction coefficient increases while the value optical b...

Investigation of optical and electrical properties of amorphous Se95−xSxZn5(x=0.2, 2, 5 and 10) thin films

In this study, we reported that the optical and electrical analysis of amorphous Se90-xSxZn5 (x=0.2, 2, 5, 10) thin films. Bulk samples of the investigated material were prepared by melt quenching technique. Thin films of ~ 300nm thickness were deposited on cleaned glass substrates by thermal evaporation technique. The morphological study of the investigated material in powder form carried out by scanning electron microscopy (SEM) confirms the disorder of the material increases at lower sulfur doping (up to 5%) whereas at higher (S) doping (10%) the defects of the material decreases. The optical parameters were estimated from optical absorption spectra data measured from UV-Vis-spectrophotometer in the wavelength range 200-900 nm. It was found that the value of optical band gap (Eg) of the investigated thin films decreases up to lower S doping and increases at higher (S) doping. The other optical parameters such as absorption coefficient (α) and extinction coefficient (K) increases up to lower S doping an...

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.