Laser induced effects on ZnO targets upon ablation at 266 and 308nm wavelengths

Abstract

The development of structural changes in ZnO targets, upon laser irradiation at the wavelengths of 266 and 308 nm, is studied by Raman spectroscopy. At the wavelength of 308 nm, oxygen vacancies are found to develop monotonically with increasing laser intensity. At 266 nm, a structural change in the irradiated ZnO targets, possibly related to nanostructuring, is observed above the laser fluence of 0.45 J cm −2 . The different natures of the laser target interaction processes taking place at both wavelengths are investigated through the characterization of the composition and energy distribution of the species ejected in the ablation. The energy of the neutral Zn and Zn 2 present in the ablation at 308 nm shows a smooth dependence on laser fluence which is consistent with the observed smooth development of oxygen vacancies. At 266 nm, the average kinetic energy of the ejected fragments is higher than at 308 nm and changes abruptly with the ablating laser fluence, consistently with the presence of a fluence threshold above which structural transform is observed at this wavelength. The plume shows the same neutral composition ͑Zn, ZnO, and Zn 2 ͒ at both wavelengths but the dependence on fluence of the ratio of neutral atomic Zn to the dimer Zn 2 shows significant differences. From the latter, different temperature regimes can be inferred in the plume generated at both wavelengths. At 266 nm the cationic composition of the plume is mainly stoichiometric whereas at 308 nm ZnO 2͑3͒ H 2͑1͒ + cations have the highest intensity.

Deposition and composition-control of Mn-doped ZnO thin films by combinatorial pulsed laser deposition using two delayed plasma plumes

“…The presence of neutral species under similar experimental conditions has been observed by optical emission spectroscopy 40 and time of flight mass spectroscopy. 41 In this set of images, it is also possible to observe emission from the upper region of the ZnO plume. This emission is completely unobservable if the second plume is not produced indicating that there is no presence of excited species or that they cannot be detected for the used value of gating time (100 ns).…”

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

“…Indium phosphide clusters produced by PLA in a carrier gas were found to be highly indium-rich [16] and essentially stoichiometric [17]. The cluster size and stoichiometry depend on various PLA parameters such as laser intensity and wavelength as well as ambient gas environment [10,[18][19][20]. Moreover, the composition the irradiated sample can vary from pulse to pulse due to non-congruent vaporization resulting in enrichment of a surface layer with a less volatile component [21,22].…”

UV-laser-induced orientation of ZnO seed layer crystals for the growth of ZnO nanorods

“…1(a)-1(c) at the center of the laser-irradiated area, which probably has a higher laser intensity. Taking into account that the laser intensity used in our study was much higher than the ablation threshold (∼0.45 J=cm 2 ), 15) the surface of a ZnO seed layer is expected to be ablated to possibly form a granular surface. Regarding the fact that seed layers of 300 nm thickness are seen to be partially peeled via laser irradiation, a thin seed layer (150 nm thick) is believed to be appropriate for efficient laser annealing while maintaining its continuous layer, a though its surface is slightly roughened by laser ablation.…”