Anwar Latif - Academia.edu (original) (raw)
Papers by Anwar Latif
Journal of Modern Physics, 2011
The micro structural morphological investigations of the laser exposed samples of Platinum are pr... more The micro structural morphological investigations of the laser exposed samples of Platinum are presented. Q-Switched Nd: YAG laser (1064 nm, 1.1 MW, 9 -14 ns) represented by Gaussian profile, power density 3 × 10 15 Watt/m 2 and focal spot size 12 µm is used to irradiate the targets (4 N, 1 × 1 × 0.3 cm 3 ). Surface modifications are observed and examined for optimized 50 pulses in air (1 atm) as well as under vacuum (~10 -3 torr) by analyzing SEM micrographs. Ripples, cones, crater and hillocks formation, splashing, sputtering, solidification and redeposition are observed as main modifications at the irradiated surface. It is explored that material is ejected with explosive expel. Motic digital microscope is used for the measurements of ablated micron sized droplets. The average distance between the adjacent cones is larger near the crater region. Topographical changes are characterized applying Atomic Force Microscopy. RMS surface roughness, hillocks and crater sizes on the irradiated surfaces are also calculated. The structural analysis is mainly focused on measurements of grain sizes, diffracted X-Rays intensity and interplanar distance. The results thus obtained determine that IR radiations are unable to change interplanar distance of the target where as changes in diffracted x-rays intensity and grain sizes for irradiated platinum are noticed.
Physica B-condensed Matter, 2011
The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG la... more The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG laser (1064 nm, ∼12 ns nominal, 1.1 MW) is used to irradiate 4 N pure (99.99%) fine polished and annealed silver samples in ambient air and under vacuum ∼10−6 Torr. The laser spot size and power density at tight focus are 12 μm and 3×1011 W/cm2, respectively. SEM micrographs and X-ray diffractograms of the exposed and unexposed targets reveal the surface texture and structural changes, respectively. Amongst the ablation mechanisms involved, exfoliation and hydrodynamic sputtering are found to be dominant. Surface modifications appear in the form of craters and ripples formation. Heat is conducted non-uniformly through narrow channels at the surface. Thermal stresses induced by the laser do not disturb inter planar distance of the target. On the other hand irradiation causes significant variations in grain size and diffracted X-rays intensities.
Physica B-condensed Matter, 2010
Ion bombarded polycrystalline fine polished silver surfaces are exposed to Nd:YAG (1064 nm, 10 mJ... more Ion bombarded polycrystalline fine polished silver surfaces are exposed to Nd:YAG (1064 nm, 10 mJ, 12 ns) and KrF excimer (248 nm, 57 mJ, 20 ns) lasers to examine structural and morphological changes employing X-ray diffractometry and optical microscopy, respectively. Irradiation causes considerable changes in grain sizes. Hydrodynamic sputtering is found to be dominant in heat affected zones (HAZs). Craters with irregular boundary and non-uniform thermal conduction are resulted on laser ablated surfaces of ion bombarded specimens. No disturbance takes place in the d-spacing of the planes of irradiated samples.
Investigations on the laser irradiation effects on gold are explored in terms of plasma-plume dyn... more Investigations on the laser irradiation effects on gold are explored in terms of plasma-plume dynamics and morphological and crystallographic changes. Annealed 4N gold samples were irradiated with a Q-switched Nd:YAG laser (53 mJ, 21 MW, 532 nm, and pulse width 6–8 ns) for plume dynamics using 10-ns gated fast photography. A Q-switched pulsed Nd:YAG laser (10 mJ, 1.1 MW, 1064 nm, and pulse width 9 ns) was used to irradiate the surface of the samples for morphological and crystallographic studies of laser-irradiated gold in a vacuum ∼10−3 Torr. The annealed samples were exposed to 50 shots of a Nd:YAG laser (10 mJ, 1.1 MW, 1064 nm, and pulse width 9 ns). The investigation on the plume was done by using an intensified charged-couple device ICCD-5760/IR-UV camera. The morphological investigation of the irradiated surface was carried out by analyzing micrographs obtained using an Hitachi S 3000 H scanning-electron microscope (SEM). The crystallographic studies of the irradiated samples were performed by analyzing the XRD patterns obtained using an X’ Pert Pro Pan Analytical X-ray diffractometer. The investigation on gated ICCD images of the plume reveal that, at very earlier times, the plasma-plume expansion has a linear trend, whereas, at later times, the plasma-plume expansion is nonuniform. SEM micrographs exhibit the primary mechanisms of pulsed-laser ablation (PLA), such as hydrodynamic sputtering, thermal sputtering, exfoliation sputtering, and splashing. The surface morphology was explained in terms of crater formation, swelling, burning, nucleation, grain growth, and nonsymmetric heat conduction. The nonuniform thermal expansion of gold due to thermal-energy transfer is also studied by SEM micrographs, which was supported by XRD analysis. The structural analysis on the basis of XRD shows that the composition of the irradiated samples is not disturbed even after laser irradiation. The grain sizes also changed due to laser irradiation.
Physica B: Condensed Matter, 2011
... [2] Muhammad Shahbaz Anwar, Anwar Latif, M. Iqbal, M. Shahid Rafique, M. Khaleeq-ur-Rahman, S... more ... [2] Muhammad Shahbaz Anwar, Anwar Latif, M. Iqbal, M. Shahid Rafique, M. Khaleeq-ur-Rahman, Sofia Siddique, Laser and Particle Beams 24 (2006) 347 [3] MS Rafique, M. Khaleeq-Ur-Rahman, T. Firdous, K. Aslam, M. Shahbaz Anwar, M. Imran , H. Latif, Laser Phys. ...
Laser and Particle Beams, 2009
Annealed and fine polished Ag and Cu samples are irradiated for 25, 50, 75, and 100 shots with a ... more Annealed and fine polished Ag and Cu samples are irradiated for 25, 50, 75, and 100 shots with a Q-Switched Nd:YAG laser in air and under high vacuum 10 26 Torr. The irradiated samples are investigated under scanning electron microscopy, which reveals the formation of laser induced ripples structures with spacing 10 mm to 25 mm. Careful analysis revealed that the ripple spacing is not only dependent on laser wavelength, target properties, but also on the number of laser shots. It is also observed that ripples spacing varies from center to edge of the thermal damage zone. Two-fold spacing is measured near the edge compared to spacing at the center of the crater. Anisotropic stresses and stress waves (shock waves) are guiding the laser induced heat energy through particular channels. Splashing cones are developed with the increase in the laser shots. More theoretical investigations are needed to study the laser ripple periodicity in the context of laser shots effect.
Radiation Effects and Defects in Solids, 2012
Fine polished 4N (99.99%) pure copper samples are irradiated in ambient air using Q-Switched Nd:Y... more Fine polished 4N (99.99%) pure copper samples are irradiated in ambient air using Q-Switched Nd:YAG Laser (10 mJ, 9–12 ns, 1064 nm). The laser energy density and spot size at tight focus are 3×1011 W/cm2 and ∼12 μm, respectively. The laser-produced crater is analyzed considering its dimensional changes with the increase in laser shots employing optical microscopy. The width of the crater (along horizontal) increases, thereby exhibiting its exponential trend. The length along the vertical and the depth of the crater both increase exponentially. The heat-affected zone expands exponentially as well. Hydrodynamics and exfoliation are the two main dominant observed ablation mechanisms.
Radiation Effects and Defects in Solids, 2012
Laser-induced modifications on platinum (Pt) and silicon (Si) are compared by considering the dev... more Laser-induced modifications on platinum (Pt) and silicon (Si) are compared by considering the development of various features on the irradiated surface. The experiments were carried out both in air and under vacuum. The interaction of 50 pulses of 1064 nm Nd:YAG laser with both targets in air resulted in nonlinear phenomena. The periphery of the irradiated spot on the Pt surface exhibits wave-like patterns with a featureless central portion. A non-uniform distribution of cones of different sizes is also observed on the irradiated surface. In the case of silicon, the laser-induced periodic surface structures along with the formation of micro-column, rectangular blocks and grid are prominently observed features. However, when both the targets were irradiated with the same number of shots under vacuum (∼10 −3 Torr), the surface morphologies of both the targets exhibited the hydrodynamic sputtering but with more explosive expulsion in Pt when compared with silicon. In platinum, there is a periodic variation in the distance between adjacent cones formed in various ablated zones. The Gaussian beam mode TEM 00 provided the evidences for melt pool formation in silicon when irradiated under vacuum. Additionally, we observed other mechanisms including splashing, sputtering, burning, re-solidification and redeposition on the surface of irradiated targets.
Radiation Effects and Defects in Solids, 2009
Laser and Particle Beams, 2006
... 348 MS Anwar et al. Page 3. Under these assumptions, above Eq. ~1! can be written for electro... more ... 348 MS Anwar et al. Page 3. Under these assumptions, above Eq. ~1! can be written for electrons as, Q Ke dTe dx . ~2! Where, Ke is the electronic thermal conductivity and Te is the electron temperature. Eq. ~2! can be solved as, ke dTe Q dx. ~3! ...
Journal of Modern Physics, 2011
The micro structural morphological investigations of the laser exposed samples of Platinum are pr... more The micro structural morphological investigations of the laser exposed samples of Platinum are presented. Q-Switched Nd: YAG laser (1064 nm, 1.1 MW, 9 -14 ns) represented by Gaussian profile, power density 3 × 10 15 Watt/m 2 and focal spot size 12 µm is used to irradiate the targets (4 N, 1 × 1 × 0.3 cm 3 ). Surface modifications are observed and examined for optimized 50 pulses in air (1 atm) as well as under vacuum (~10 -3 torr) by analyzing SEM micrographs. Ripples, cones, crater and hillocks formation, splashing, sputtering, solidification and redeposition are observed as main modifications at the irradiated surface. It is explored that material is ejected with explosive expel. Motic digital microscope is used for the measurements of ablated micron sized droplets. The average distance between the adjacent cones is larger near the crater region. Topographical changes are characterized applying Atomic Force Microscopy. RMS surface roughness, hillocks and crater sizes on the irradiated surfaces are also calculated. The structural analysis is mainly focused on measurements of grain sizes, diffracted X-Rays intensity and interplanar distance. The results thus obtained determine that IR radiations are unable to change interplanar distance of the target where as changes in diffracted x-rays intensity and grain sizes for irradiated platinum are noticed.
Physica B-condensed Matter, 2011
The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG la... more The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG laser (1064 nm, ∼12 ns nominal, 1.1 MW) is used to irradiate 4 N pure (99.99%) fine polished and annealed silver samples in ambient air and under vacuum ∼10−6 Torr. The laser spot size and power density at tight focus are 12 μm and 3×1011 W/cm2, respectively. SEM micrographs and X-ray diffractograms of the exposed and unexposed targets reveal the surface texture and structural changes, respectively. Amongst the ablation mechanisms involved, exfoliation and hydrodynamic sputtering are found to be dominant. Surface modifications appear in the form of craters and ripples formation. Heat is conducted non-uniformly through narrow channels at the surface. Thermal stresses induced by the laser do not disturb inter planar distance of the target. On the other hand irradiation causes significant variations in grain size and diffracted X-rays intensities.
Physica B-condensed Matter, 2010
Ion bombarded polycrystalline fine polished silver surfaces are exposed to Nd:YAG (1064 nm, 10 mJ... more Ion bombarded polycrystalline fine polished silver surfaces are exposed to Nd:YAG (1064 nm, 10 mJ, 12 ns) and KrF excimer (248 nm, 57 mJ, 20 ns) lasers to examine structural and morphological changes employing X-ray diffractometry and optical microscopy, respectively. Irradiation causes considerable changes in grain sizes. Hydrodynamic sputtering is found to be dominant in heat affected zones (HAZs). Craters with irregular boundary and non-uniform thermal conduction are resulted on laser ablated surfaces of ion bombarded specimens. No disturbance takes place in the d-spacing of the planes of irradiated samples.
Investigations on the laser irradiation effects on gold are explored in terms of plasma-plume dyn... more Investigations on the laser irradiation effects on gold are explored in terms of plasma-plume dynamics and morphological and crystallographic changes. Annealed 4N gold samples were irradiated with a Q-switched Nd:YAG laser (53 mJ, 21 MW, 532 nm, and pulse width 6–8 ns) for plume dynamics using 10-ns gated fast photography. A Q-switched pulsed Nd:YAG laser (10 mJ, 1.1 MW, 1064 nm, and pulse width 9 ns) was used to irradiate the surface of the samples for morphological and crystallographic studies of laser-irradiated gold in a vacuum ∼10−3 Torr. The annealed samples were exposed to 50 shots of a Nd:YAG laser (10 mJ, 1.1 MW, 1064 nm, and pulse width 9 ns). The investigation on the plume was done by using an intensified charged-couple device ICCD-5760/IR-UV camera. The morphological investigation of the irradiated surface was carried out by analyzing micrographs obtained using an Hitachi S 3000 H scanning-electron microscope (SEM). The crystallographic studies of the irradiated samples were performed by analyzing the XRD patterns obtained using an X’ Pert Pro Pan Analytical X-ray diffractometer. The investigation on gated ICCD images of the plume reveal that, at very earlier times, the plasma-plume expansion has a linear trend, whereas, at later times, the plasma-plume expansion is nonuniform. SEM micrographs exhibit the primary mechanisms of pulsed-laser ablation (PLA), such as hydrodynamic sputtering, thermal sputtering, exfoliation sputtering, and splashing. The surface morphology was explained in terms of crater formation, swelling, burning, nucleation, grain growth, and nonsymmetric heat conduction. The nonuniform thermal expansion of gold due to thermal-energy transfer is also studied by SEM micrographs, which was supported by XRD analysis. The structural analysis on the basis of XRD shows that the composition of the irradiated samples is not disturbed even after laser irradiation. The grain sizes also changed due to laser irradiation.
Physica B: Condensed Matter, 2011
... [2] Muhammad Shahbaz Anwar, Anwar Latif, M. Iqbal, M. Shahid Rafique, M. Khaleeq-ur-Rahman, S... more ... [2] Muhammad Shahbaz Anwar, Anwar Latif, M. Iqbal, M. Shahid Rafique, M. Khaleeq-ur-Rahman, Sofia Siddique, Laser and Particle Beams 24 (2006) 347 [3] MS Rafique, M. Khaleeq-Ur-Rahman, T. Firdous, K. Aslam, M. Shahbaz Anwar, M. Imran , H. Latif, Laser Phys. ...
Laser and Particle Beams, 2009
Annealed and fine polished Ag and Cu samples are irradiated for 25, 50, 75, and 100 shots with a ... more Annealed and fine polished Ag and Cu samples are irradiated for 25, 50, 75, and 100 shots with a Q-Switched Nd:YAG laser in air and under high vacuum 10 26 Torr. The irradiated samples are investigated under scanning electron microscopy, which reveals the formation of laser induced ripples structures with spacing 10 mm to 25 mm. Careful analysis revealed that the ripple spacing is not only dependent on laser wavelength, target properties, but also on the number of laser shots. It is also observed that ripples spacing varies from center to edge of the thermal damage zone. Two-fold spacing is measured near the edge compared to spacing at the center of the crater. Anisotropic stresses and stress waves (shock waves) are guiding the laser induced heat energy through particular channels. Splashing cones are developed with the increase in the laser shots. More theoretical investigations are needed to study the laser ripple periodicity in the context of laser shots effect.
Radiation Effects and Defects in Solids, 2012
Fine polished 4N (99.99%) pure copper samples are irradiated in ambient air using Q-Switched Nd:Y... more Fine polished 4N (99.99%) pure copper samples are irradiated in ambient air using Q-Switched Nd:YAG Laser (10 mJ, 9–12 ns, 1064 nm). The laser energy density and spot size at tight focus are 3×1011 W/cm2 and ∼12 μm, respectively. The laser-produced crater is analyzed considering its dimensional changes with the increase in laser shots employing optical microscopy. The width of the crater (along horizontal) increases, thereby exhibiting its exponential trend. The length along the vertical and the depth of the crater both increase exponentially. The heat-affected zone expands exponentially as well. Hydrodynamics and exfoliation are the two main dominant observed ablation mechanisms.
Radiation Effects and Defects in Solids, 2012
Laser-induced modifications on platinum (Pt) and silicon (Si) are compared by considering the dev... more Laser-induced modifications on platinum (Pt) and silicon (Si) are compared by considering the development of various features on the irradiated surface. The experiments were carried out both in air and under vacuum. The interaction of 50 pulses of 1064 nm Nd:YAG laser with both targets in air resulted in nonlinear phenomena. The periphery of the irradiated spot on the Pt surface exhibits wave-like patterns with a featureless central portion. A non-uniform distribution of cones of different sizes is also observed on the irradiated surface. In the case of silicon, the laser-induced periodic surface structures along with the formation of micro-column, rectangular blocks and grid are prominently observed features. However, when both the targets were irradiated with the same number of shots under vacuum (∼10 −3 Torr), the surface morphologies of both the targets exhibited the hydrodynamic sputtering but with more explosive expulsion in Pt when compared with silicon. In platinum, there is a periodic variation in the distance between adjacent cones formed in various ablated zones. The Gaussian beam mode TEM 00 provided the evidences for melt pool formation in silicon when irradiated under vacuum. Additionally, we observed other mechanisms including splashing, sputtering, burning, re-solidification and redeposition on the surface of irradiated targets.
Radiation Effects and Defects in Solids, 2009
Laser and Particle Beams, 2006
... 348 MS Anwar et al. Page 3. Under these assumptions, above Eq. ~1! can be written for electro... more ... 348 MS Anwar et al. Page 3. Under these assumptions, above Eq. ~1! can be written for electrons as, Q Ke dTe dx . ~2! Where, Ke is the electronic thermal conductivity and Te is the electron temperature. Eq. ~2! can be solved as, ke dTe Q dx. ~3! ...