Dilawar Ali

Characterization of laser-produced plasma ions of various metals and their effect on the optical properties of the CR-39 polymer

The laser-produced plasma (LPP) ions of various metals (Mo, Ni, Cu, Ti and Zn) was implanted in CR-39 polymer, and their influence on its optical properties was investigated. The plasma of these metals was produced using 200 shots of a Q-switched Nd:YAG pulsed laser in a vacuum of 10−3 Torr. The CR-39 specimens were exposed to LPP ions (flux: F=8.01×109−22.14×109 ions/m2, average energy: E av=52−297 keV) emitted along the normal to the metal surface in each case. Both F and E av were found to be a function of the room temperature Debye–Waller thermal parameter B and increase with increase in B-value. The structural behavior of virgin and implanted specimens was investigated using a ultra violet (UV)–visible spectrophotometer. The value of disorder content (Urbach energy E u) was found to lie in the range of 0.287–0.377 eV. The optical band gap energy (E g) for indirect transition decreased on implantation with metallic LPP ions, whereas such a variation in the case of direct transition was negligible. It was observed that E g for indirect transition increases with the increase in E u, whereas the dependence of E g for direct transition on E u was negligible.

Surface topography and structure of laser-treated high-purity zinc

We irradiated 99.995% pure zinc specimens in a vacuum with 50, 60, 70, 80, 90, and 100 nanosecond visible laser shots. SEM images of irradiated specimens were analyzed using Gwyddion 2.29 software. The average length of surface microcones formed at the periphery of the ablated area increases linearly from 30 to 56 μm on the increase in number of laser shots from 50 to 100. Nano-size droplets (16–40 nm) are formed in the vicinity of ablated area; the greater the number of droplets, the smaller is their mean diameter. XRD patterns of un-irradiated and irradiated specimens reveal changes in the intensity of diffracted peaks on laser irradiation. Harris analysis was done to determine texture coefficient; crystallographic planes (002) and (004) get preferentially oriented on laser irradiation. Williamson–Hall analysis was carried out to evaluate the structural parameters, namely crystallite size, dislocation line density, and microstrain.

Impact of 532 nm 6 ns laser pulses on (104) oriented zinc single crystal: surface morphology, phase transformation, and structure hardness relationship

Specimens of (104) oriented Zn single crystal were irradiated in vacuum ~10−3 Torr with pulsed Nd:YAG laser (λ = 532 nm, E = 50 mJ, τ = 6 ns) at a repetition rate 10 Hz. The number of laser shots was varied from 1 to 100. The laser fluence and laser intensity at the one laser shot irradiation spot on the target surface were 97.2 J cm−2 and 1.6 × 1010 W cm−2, respectively. Crater geometry of laser-irradiated specimens was examined by optical microscope. Crater area was found to increase with the increase in number of laser shots. The data points were encompassed by sigmoidal (Boltzmann) fit showing that crater area increases rapidly to begin with up to 50 laser shots and later on rather slowly till 100 laser shots. Surface morphology was examined by SEM and AFM, which revealed ripple patterns, cavities, trenches, ridges, nanohillocks, microcones, droplets, and solid flakes etc. Structural parameters, namely crystallite size and lattice strain were evaluated by Williamson–Hall analysis of x-ray diffraction patterns. Surface hardness was found to increase up to 50 laser shots and later on it decreased progressively till 100 laser shots. Correlation between surface hardness and crystallite size was also examined, and was found to obey inverse Hall–Petch relation.

Optical, structural, and chemical properties of CR-39 implanted with 5.2 MeV doubly charged carbon ions

Poly-allyl-diglycol-carbonate (CR-39) specimens were irradiated with 5.2 MeV doubly charged carbon ions using Pelletron accelerator. Ion dose was varied from 5 × 1013 to 5 × 1015 ions cm−2. Optical, structural, and chemical properties were investigated by UV–vis spectroscopy, x-ray diffractometer, and FTIR/Raman spectroscopy, respectively. It was found that optical absorption increases with increasing ion dose. Absorption edge shifts from UV region to visible region. The measured opacity values of pristine and ion implanted CR-39 range from 0.0519 to 4.7959 mm−1 following an exponential growth (9141%) with the increase in ion dose. The values of direct and indirect band gap energy decrease exponentially with an increase in ion dose by 59% and 71%, respectively. However, average refractive index in the visible region increases from 1.443 to 2.864 with an increase in ion dose, by 98%. A linear relation between band gap energy and crystallite size was observed. Both the number of carbon atoms in conjugation length and the number of carbon atoms per cluster increase linearly with the increase in ion dose. FTIR spectra showed that on C+2 ions irradiation, the intensity of all bands decreases gradually without appearance of any new band, indicating degradation of polymer after irradiation. Raman spectra revealed that the density of −CH2− group decreases on C+2 ions irradiation. However, the structure of CR-39 is completely destroyed on irradiation with ion dose 1 × 1015 and 5 × 1015 ions cm−2.