TY - JOUR A1 - Beke, S. A1 - Sugioka, K. A1 - Midorikawa, K. A1 - Péter, Á. A1 - Nánai, L. A1 - Bonse, Jörn T1 - Characterization of the ablation of TeO2 crystals in air with femtosecond laser pulses N2 - Femtosecond (fs) laser pulse ablation (pulse duration of 150 fs, wavelength of 775 nm, repetition rate of 1 kHz) of single-crystalline TeO2 surfaces was performed in air using the direct focusing technique. The lateral and vertical dimensions of laser ablated craters as well as the laser damage thresholds were evaluated for different pulse numbers applied to the same spot. The joint observation using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters and also showed that the ablation threshold depends significantly on the number of laser pulses applied to the same spot due to incubation effects. The incubation effects change the absorption processes involved in fs-laser ablation of the transparent material from multiphoton absorption to a single-photon absorption. These results are discussed on the basis of recent models of the interaction of fs-laser pulses with dielectrics. KW - Femtosecond laser ablation KW - Damage threshold KW - TeO2 KW - Dielectrics PY - 2010 U6 - https://doi.org/10.1088/0022-3727/43/2/025401 SN - 0022-3727 SN - 1361-6463 VL - 43 IS - 2 SP - 025401-1 - 025401-6 PB - IOP Publ. CY - Bristol AN - OPUS4-20665 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Probing the heat affected zone by chemical modifications in femtosecond pulse laser ablation of titanium nitride films in air N2 - A new approach is presented to quantify the so-called "heat affected zone" (HAZ) during femtosecond laser pulse processing. Ablation of titanium nitride (TiN) thin films (~3 μm thickness) by multiple femtosecond laser pulses (τ=130 fs, λ=800 nm) in air environment was studied by means of two different surface analytical methods both being sensitive to chemical alterations at the surface. Scanning Auger electron microscopy was applied for a visualization of the spatial distribution of specific elements (Ti, O) within the laser-modified areas. The chemical state of the irradiated surface was revealed by complementary x-ray photoelectron spectroscopy. Both methods were used for a depth-profiling chemical analysis (tracking the elements Ti, N, O, and C) using an Ar-ion beam for surface sputtering. In a narrow laser fluence range slightly below the ablation threshold of TiN significant superficial oxidation can be observed leading to the formation of substoichiometric TiO2-x. At fluences above the ablation threshold, an increased titanium concentration is observed within the entire ablation craters. Following upon sputter removal the elemental distribution into the depth of the nonablated material, the results allow an estimation of the heat-affected zone for femtosecond laser ablation in air environment. According to our analyses, the HAZ extends up to a few hundreds of nanometers into the nonablated material. KW - Femtosecond laser ablation KW - Heat affected zone KW - Titanium nitride KW - Scanning Auger electron microscopy KW - X-ray KW - Photoelektron spectroscopy PY - 2010 UR - http://link.aip.org/link/?JAP/107/054902 U6 - https://doi.org/10.1063/1.3311552 SN - 0021-8979 SN - 1089-7550 VL - 107 IS - 5 SP - 054902-1 - 054902-5 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-20949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Puerto, D. A1 - Siegel, J. A1 - Gawelda, W. A1 - Galvan-Sosa, M. A1 - Ehrentraut, L. A1 - Bonse, Jörn A1 - Solis, J. T1 - Dynamics of plasma formation, relaxation, and topography modification induced by femtosecond laser pulses in crystalline and amorphous dielectrics N2 - We have studied plasma formation and relaxation dynamics along with the corresponding topography modifications in fused silica and sapphire induced by single femtosecond laser pulses (800 nm and 120 fs). These materials, representative of high bandgap amorphous and crystalline dielectrics, respectively, require nonlinear mechanisms to absorb the laser light. The study employed a femtosecond time-resolved microscopy technique that allows obtaining reflectivity and transmission images of the material surface at well-defined temporal delays after the arrival of the pump pulse which excites the dielectric material. The transient evolution of the free-electron plasma formed can be followed by combining the time-resolved optical data with a Drude model to estimate transient electron densities and skin depths. The temporal evolution of the optical properties is very similar in both materials within the first few hundred picoseconds, including the formation of a high reflectivity ring at about 7 ps. In contrast, at longer delays (100 ps–20 ns) the behavior of both materials differs significantly, revealing a longer lasting ablation process in sapphire. Moreover, transient images of sapphire show a concentric ring pattern surrounding the ablation crater, which is not observed in fused silica. We attribute this phenomenon to optical diffraction at a transient elevation of the ejected molten material at the crater border. On the other hand, the final topography of the ablation crater is radically different for each material. While in fused silica a relatively smooth crater with two distinct regimes is observed, sapphire shows much steeper crater walls, surrounded by a weak depression along with cracks in the material surface. These differences are explained in terms of the most relevant thermal and mechanical properties of the material. Despite these differences the maximum crater depth is comparable in both material at the highest fluences used (16J/cm2). The evolution of the crater depth as a function of fluence can be described taking into account the individual bandgap of each material. KW - Femtosecond laser ablation KW - Plasma formation KW - Time-resolved microscopy KW - Dielectrics KW - Fused silica KW - Sapphire KW - Scanning force microscopy KW - Reflectivity measurements KW - Transmission measurements KW - Drude model PY - 2010 U6 - https://doi.org/10.1364/JOSAB.27.001065 SN - 0740-3224 SN - 1520-8540 VL - 27 IS - 5 SP - 1065 EP - 1076 PB - Optical Society of America CY - Washington, DC AN - OPUS4-21167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Bachelier, G. A1 - Wiggins, S. M. A1 - Siegel, J. A1 - Solis, J. A1 - Krüger, Jörg A1 - Sturm, Heinz T1 - Femtosecond laser ablation of indium phosphide in air: dynamical, structural and morphological evolution N2 - The irradiation of single-crystalline indium phosphide (c-InP) by Ti:sapphire femtosecond laser pulses (130 fs, 800 nm) in air is studied by means of in-situ time resolved reflectivity measurements [fs-time-resolved microscopy (100 fs-10 ns) and point probing analysis (ns - µs)] and by complementary ex-situ surface analytical methods (Micro Raman Spectroscopy, Scanning Force, and Optical Microscopy). The dynamics of melting, ablation, and optical breakdown as well as structural changes resulting from rapid solidification are investigated in detail. Different laser-induced surface morphologies are characterized and discussed on the basis of recent ablation and optical breakdown models. KW - Femtosecond laser ablation KW - Optical breakdown KW - Time-resolved measurements KW - Semiconductor KW - Indium phosphide PY - 2010 SN - 1454-4164 VL - 12 IS - 3 SP - 421 EP - 426 PB - INOE & INFM CY - Bucharest AN - OPUS4-21082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sokolowski-Tinten, K. A1 - Barty, A. A1 - Boutet, S. A1 - Shymanovich, U. A1 - Bogan, M. A1 - Marchesini, S. A1 - Hau-Riege, S. A1 - Stojanovic, N. A1 - Bonse, Jörn A1 - Tobey, R. A1 - Ehrke, H. A1 - Cavalleri, A. A1 - Duesterer, S. A1 - Frank, M. A1 - Bajt, S. A1 - Schulz, J. A1 - Seibert, M. A1 - Hajdu, J. A1 - Treusch, R. A1 - Chapman, H. T1 - Short-pulse laser induced transient structure formation and ablation studied with time-resolved coherent XUV-scattering N2 - XUV- and X-ray free-electron-lasers (FEL) combine short wavelength, ultrashort pulse duration, spatial coherence and high intensity. This unique combination of properties opens up new possibilities to study the dynamics of non-reversible phenomena with ultrafast temporal and nano- to atomic-scale spatial resolution. In this contribution we wish to present results of time-resolved experiments performed at the XUV-FEL FLASH (HASYLAB/Hamburg) aimed to investigate the nano-scale structural dynamics of laser-irradiated materials. Thin films and fabricated nano-structures, deposited on Si3N4-membranes, have been excited with ultrashort optical laser pulses. The dynamics of the non-reversible structural evolution of the irradiated samples during laser-induced melting and ablation has been studied in an optical pump - XUV-probe configuration by means of single-shot coherent scattering techniques (i.e. diffraction imaging [1]). In a first set of experiments we investigated the formation of laser induced periodic surface structures (LIPSS) on the surface of thin Si-films (thickness 100 nm). In a simplified view LIPPS are generated as a result of interference between the incident laser pulse and surface scattered waves which leads to a periodically modulated energy deposition. Time-resolved scattering using femtosecond XUV-pulses (with a wavelength of 13.5 nm and 7 nm) allowed us to directly follow LIPSS evolution on an ultrafast time-scale and with better than 40 nm spatial resolution. The observed scattering patterns show almost quantitative agreement with theoretical predictions [2] and reveal that the LIPSS start to form already during the 12 ps pump pulse. In the second set of measurements we studied picosecond and femtosecond laser induced ablation and disintegration of fabricated nano-structures. Correlations of coherent diffraction patterns measured at various time delays to the pattern of the undisturbed object show that order in the structure is progressively lost starting from short length scales. This structural rearrangement progresses at close to the speed of sound in the material. Under certain circumstances (e.g. adequate sampling) it became also possible to reconstruct real-space images of the object as it evolves over time [3]. The possibility of femtosecond single-shot imaging of ultrafast dynamic processes with nanoscale resolution provides yet more details of the physical processes involved. [1] H. N. Chapman et al. Nature Phys. 2, 839 (2006). [2] J. F. Young et al., Phys. Rev. B 27, 1155 (1983). [3] A. Barty et al. Nature Phot. 2, 415 (2008). T2 - Fall meeting of the materials research society 2009 CY - Boston, MA, USA DA - 2009-11-30 KW - Femtosecond laser ablation KW - Laser-induced periodic surface structures KW - Time-resolved coherent XUV scattering KW - Semiconductor KW - Silicon PY - 2010 U6 - https://doi.org/10.1557/PROC-1230-MM05-03 N1 - Serientitel: Materials Research Society symposium proceedings – Series title: Materials Research Society symposium proceedings VL - 1230E IS - Paper 1230-MM05-03 SP - 1 EP - 6 AN - OPUS4-21438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sokolowski-Tinten, K. A1 - Barty, A. A1 - Boutet, S. A1 - Shymanovich, U. A1 - Chapman, H. A1 - Bogan, M. A1 - Marchesini, S. A1 - Hau-Riege, S. A1 - Stojanovic, N. A1 - Bonse, Jörn A1 - Rosandi, Y. A1 - Urbassek, H. M. A1 - Tobey, R. A1 - Ehrke, H. A1 - Cavalleri, A. A1 - Düsterer, S. A1 - Redlin, H. A1 - Frank, M. A1 - Bajt, S. A1 - Schulz, J. A1 - Seibert, M. A1 - Hajdu, J. A1 - Treusch, R. A1 - Bostedt, C. A1 - Hoener, M. A1 - Möller, T. T1 - Short-pulse laser induced transient structure formation and ablation studied with time-resolved coherent XUV-scattering T2 - International high-power laser ablation conference CY - Santa Fe, USA DA - 2010-04-18 KW - Femtosecond laser ablation KW - Free electron lasers KW - Coherent scattering PY - 2010 SN - 978-0-7354-0828-9 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1278 SP - 373 EP - 379 PB - American Institute of Physics CY - Melville, NY, USA AN - OPUS4-22230 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -