TY - GEN A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Krüger, Jörg A1 - Kautek, Wolfgang ED - Phipps, C. T1 - Femtosecond laser micromachining of technical materials N2 - Micromachining experiments were performed with Ti:sapphire laser pulses (130 fs - 150 fs, 800 nm, approximately 10 Hz) in air. Employing the direct focusing technique, highly absorbing titanium nitride (TiN) and weakly absorbing polyimide (PI) and polymethylmethacrylate (PMMA) served as target materials. The lateral and vertical precision of the laser ablation and morphological features were characterized by scanning force (SFM), scanning electron (SEM) and optical microscopy. For TiN, incubation can be observed, i.e. the single-pulse surface damage threshold (0.26 J/cm2) is by a factor of two greater than the threshold for 100 pulses. Ablation rates below 10 nm per pulse can be achieved. The evolution of sub-wavelength ripples is presented in dependence on pulse number and laser fluence, respectively. The incubation behavior of the polymers can be described by an accumulation model as for TiN. Experiments on PI with varying focal lengths result in the same modification thresholds. Different polarization states of light (linear, circular) lead to a variation of the ablation rate and to various morphological patterns in the ablation craters (wavelength ripples, cones). Swelling of PMMA occurred at fluences below the ablation threshold. T2 - 3rd SPIE's International Conference on High-Power Laser Ablation CY - Santa Fe, NM, USA DA - 24.04.2000 KW - Ablation KW - Femtosecond pulse laser KW - Laser processing KW - Micromachining KW - Polymer KW - Titanium nitride KW - Ripples PY - 2000 SN - 0-8194-3700-X U6 - https://doi.org/10.1117/12.407346 SN - 1605-7422 N1 - Serientitel: SPIE proceedings series – Series title: SPIE proceedings series IS - 4065 SP - 161 EP - 172 PB - SPIE CY - Bellingham, Wash. AN - OPUS4-967 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bonse, Jörn A1 - Krüger, Jörg A1 - Kautek, Wolfgang A1 - Wrobel, J. M. T1 - Femtosecond pulse laser machining of InP wafers N2 - Ablation of indium phosphide wafers in air was performed with 130 fs laser pulses at a wavelength of 800 nm at a low repetition rate of 10 Hz. In order to evaluate the role of the incubation effects, the relationship between the number of laser pulses used for the ablation and the threshold fluence was studied. Particular attention was paid to the chemical composition, surface morphology and structural variations of the ablated area. T2 - 5th Laser Applications in Microelectronics and Optoelectronics Manufacturing Conference (LAMOM) CY - San José, CA, USA DA - 240.01.2000 KW - Femtosecond laser ablation KW - Indium phosphide KW - Auger electron spectroscopy PY - 2000 SN - 0-8194-3550-3 SN - 1605-7422 N1 - Serientitel: SPIE proceedings series – Series title: SPIE proceedings series IS - 3933 SP - 280 EP - 287 PB - SPIE CY - Bellingham, Wash. AN - OPUS4-937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Krüger, Jörg A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Kautek, Wolfgang A1 - Lenzner, M. A1 - Wrobel, J. M. T1 - Femtosecond-Pulse Laser Machining of Semiconducting Materials N2 - Summary form only given. Machining investigations of crystalline silicon have been performed with laser pulses at a wavelength of 780 nm in the range between 5 fs and 400 fs. Applying 100 pulses per spot, surface damage thresholds were determined by the measurement of the damage diameter. In this pulse duration regime, the threshold fluences were nearly constant. Single-pulse investigations with 5 fs pulses yielded a value of about 0.15 J cm-2 identical to the multi-pulse experiment. This is in contradiction to the behaviour of dielectrics where incubation effects alter the optical properties down to the 5 fs pulse regime. Employing laser pulses with a duration of 130 fs at a wavelength of 800 nm, single-pulse ablation thresholds of 0.23 J cm-2 and 0.16 J cm-2 were determined for Si and InP in air, respectively. The threshold fluence was calculated from the linear relation between the square of the diameters versus the logarithm of the laser fluences. T2 - CLEO/Europe 2000 ; Conference on Lasers and Electro-Optics Europe ; Conférence Européenne sur les Lasers et l'Electro-Optique ; CLEO/Europe-IQEC CY - Nice, France DA - 2000-09-10 PY - 2000 SN - 0-7803-6319-1 U6 - https://doi.org/10.1109/CLEOE.2000.910410 PB - IEEE Service Center CY - Piscataway, NJ AN - OPUS4-958 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bonse, Jörn A1 - Munz, Martin A1 - Sturm, Heinz ED - Vajtai, R. T1 - Scanning force microscopic investigations of the femtosecond pulse laser ablation of indium phosphide in air N2 - Laser ablation of single-crystalline indium phosphide (InP) was performed in air by means of linearly polarized Ti:sapphire femtosecond-pulses (800 nm, 130 fs, 10 Hz). As a result of the first laser pulses, several morphological changes (crater formation, rim formation, ripple structures and cones) were observed. These effects were explored using force modulation microscopy (FMM), a technique based on scanning force microscopy (SFM), allowing the simultaneous imaging of both topography and local stiffness at a high lateral resolution. The first laser pulse induces the formation of a protruding rim (height <20 nm, width ~300 nm) bordering the ablated crater. A Fourier-analysis of the multi-pulse generated topographies reveals the formation of wavelength-sized periodic ripples (modulation depth <100 nm) with an orientation perpendicular to that of the electric field vector of the laser radiation. Besides these morphological alterations, also material modifications were observed in the irradiated regions by means of the FFM technique. Within the ablated craters, local stiffness variations were found revealing an inhomogeneous material composition/structure as a consequence of the femtosecond pulse laser treatment. T2 - Nanotechnology Conference 2003 CY - Maspalomas, Gran Canaria, Spain DA - 2003-05-19 KW - Femtosecond laser irradiation KW - Microstructure KW - Indium phosphide KW - Scanning/atomic force microscopy (SFM/AFM) KW - Stiffness KW - Laser induced periodic surface structures (LIPSS) PY - 2003 UR - http://cat.inist.fr/?aModele=afficheN&cpsidt=15329222 SN - 0-8194-4978-4 N1 - Serientitel: SPIE proceedings series – Series title: SPIE proceedings series IS - 5118 SP - 221 EP - 234 PB - SPIE, the International Society for Optical Engineering CY - Bellingham, Wash. AN - OPUS4-2865 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Rudolph, Pascale A1 - Krüger, Jörg A1 - Baudach, Steffen A1 - Kautek, Wolfgang T1 - Femtosecond pulse laser processing of TiN on silicon N2 - Ultrashort pulse laser microstructuring (pulse duration 130 fs, wavelength 800 nm, repetition rate 2 Hz) of titanium nitride (TiN) films on silicon substrates was performed in air using the direct focusing technique. The lateral and vertical precision of laser ablation was evaluated. The TiN ablation threshold changed with the number of pulses applied to the surface due to an incubation effect. An ablation depth per pulse below the penetration depth of light was observed. Columnar structures were formed in the silicon substrate after drilling through the TiN layer. KW - Femtosecond laser ablation KW - Titanium nitride KW - Silicon KW - Optical properties PY - 2000 U6 - https://doi.org/10.1016/S0169-4332(99)00481-X SN - 0169-4332 SN - 1873-5584 VL - 154-155 SP - 659 EP - 663 PB - North-Holland CY - Amsterdam AN - OPUS4-802 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baudach, Steffen A1 - Bonse, Jörn A1 - Krüger, Jörg A1 - Kautek, Wolfgang T1 - Ultrashort pulse laser ablation of polycarbonate and polymethylmethacrylate N2 - Ablation experiments with ultrashort laser pulses (pulse duration 150 fs, wavelength 800 nm) on polymers (PC, PMMA) relevant for biomedical technology have been performed in air. The lateral and vertical machining precision was evaluated by optical, atomic force and scanning electron microscopy. The ablation threshold reaches values in the range of 0.5–2.5 J/cm2 and depends significantly on the number of laser pulses applied to the same spot. The hole diameters are influenced by the laser fluence and the number of laser pulses. The relation between the ablation threshold and the number of laser pulses applied to the same spot is described in accordance with an incubation model. KW - Femtosecond laser ablation KW - Polymer KW - Polycarbonate KW - Polymethylmethacrylate PY - 2000 U6 - https://doi.org/10.1016/S0169-4332(99)00474-2 SN - 0169-4332 SN - 1873-5584 VL - 154-155 SP - 555 EP - 560 PB - North-Holland CY - Amsterdam AN - OPUS4-803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Brzezinka, Klaus-Werner A1 - Meixner, A.J. T1 - Modifying single-crystalline silicon by femtosecond laser pulses: an analysis by micro Raman spectroscopy, scanning laser microscopy and atomic force microscopy N2 - The surface modification of single-crystalline silicon induced by single 130 femtosecond (fs) Ti:sapphire laser pulses (wavelength 800 nm) in air is investigated by means of micro Raman spectroscopy (?-RS), atomic force microscopy and scanning laser microscopy. Depending on the laser fluence, in some regions the studies indicate a thin amorphous top-layer as well as ablated and recrystallized zones. The single-pulse threshold fluences for melting, ablation and polycrystalline recrystallization are determined quantitatively. Several different topographical surface structures (rims and protrusions) are found. Their formation is discussed in the context of recent studies of the laser irradiation of silicon. In combination with a thin-film optical model, the thickness of the amorphous layer is determined by two independent and nondestructive optical methods to be in the order of several 10 nm. KW - Femtosecond laser ablation KW - Silicon KW - Raman spectroscopy KW - Atomic force microscopy KW - Laser scanning microscopy PY - 2004 U6 - https://doi.org/10.1016/S0169-4332(03)00881-X SN - 0169-4332 SN - 1873-5584 VL - 221 IS - 1-4 SP - 215 EP - 230 PB - North-Holland CY - Amsterdam AN - OPUS4-3224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Sturm, Heinz A1 - Schmidt, Dieter A1 - Kautek, Wolfgang T1 - Chemical, morphological and accumulation phenomena in ultrashort-pulse laser ablation of TiN in air N2 - Ultrashort-pulse laser ablation (F=130 fs, 5=800 nm, repetition rate 2-20 Hz) of titanium nitride was investigated for laser fluences between 0.3 and 4.5 J/cm2 using the direct focusing technique in air. The influence of the laser pulse number and the peak fluence was investigated by means of several surface analytical techniques (optical microscopy, dynamic friction atomic force microscopy, scanning Auger electron microscopy and small-spot electron spectroscopy for chemical analysis). The correlation of the results about optical, physical and chemical properties of the irradiated areas allows us to propose a simple oxidation model, which explains different observed phenomena associated with surface damage such as mound formation and crater widening and clarifies the incubation behavior reported earlier for this material. PY - 2000 U6 - https://doi.org/10.1007/s003390000585 SN - 0947-8396 VL - 71 IS - 6 SP - 657 EP - 665 PB - Springer CY - Berlin AN - OPUS4-1067 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Wrobel, Jerzy A1 - Krüger, Jörg A1 - Kautek, Wolfgang T1 - Ultrashort-pulse laser ablation of indium phosphide in air N2 - Ablation of indium phosphide wafers in air was performed with low repetition rate ultrashort laser pulses (130 fs, 10 Hz) of 800 nm wavelength. The relationships between the dimensions of the craters and the ablation parameters were analyzed. The ablation threshold fluence depends on the number of pulses applied to the same spot. The single-pulse ablation threshold value was estimated to be fth(1)=0.16 J/cm2. The dependence of the threshold fluence on the number of laser pulses indicates an incubation effect. Morphological and chemical changes of the ablated regions were characterized by means of scanning electron microscopy and Auger electron spectroscopy. PY - 2001 U6 - https://doi.org/10.1007/s003390000596 SN - 0947-8396 VL - 72 IS - 1 SP - 89 EP - 94 PB - Springer CY - Berlin AN - OPUS4-1068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Kautek, Wolfgang A1 - Geuss, Markus A1 - Sturm, Heinz T1 - The precision of the femtosecond-pulse laser ablation of TiN films on silicon N2 - Ti:sapphire laser pulses of 130 fs and 800 nm were focused on 3.2-7m-thick TiN films by a 60-mm focal length lens in air. The morphology of the ablated areas generated by laser pulses at a fluence slightly above the ablation threshold was characterized in dependence on the pulse number by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The cavity profiles, depths, diameters, and volumes were quantitatively evaluated by AFM. The polarization state of the laser light is discussed as a further parameter, in addition to fluence and pulse number, that influences and controls the ablation precision of these materials. It was observed that circularly polarized radiation enhances the average ablation rates and reduces the roughness in the cavities by a factor of 2-3 as compared to linearly polarized radiation of the same incident laser fluence. Special attention was paid to the interfacial region between the coating and substrate. Ultrashort-pulse laser drilling into the Si substrate revealed the generation of columnar features which even may surmount the original coating under laser conditions. T2 - 5th International Conference on Laser Ablation ; COLA '99 CY - Göttingen, Germany DA - 1999-07-19 KW - Laser ablation KW - Picosecond PY - 1999 U6 - https://doi.org/10.1007/s003390051425 SN - 0947-8396 VL - 69 IS - 7 SP - S399 EP - S402 PB - Springer CY - Berlin AN - OPUS4-778 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baudach, Steffen A1 - Bonse, Jörn A1 - Kautek, Wolfgang T1 - Ablation experiments on polyimide with femtosecond laser pulses N2 - Some applications of polymer films require the microstructuring of partly uneven substrates. This cannot be achieved by conventional photolithography, usually performed with ultraviolet short-pulse lasers (excimer, fourth harmonic Nd:YAG). When processing thermally sensitive or undoped polymers with low optical absorption, the use of femtosecond laser pulses can improve the ablation precision, also reducing the heat-affected zone. Therefore, a Ti:sapphire laser system was employed to perform ablation experiments on polyimide (PI). The irradiated areas were evaluated by means of optical and scanning electron microscopy. Highly oriented ripple structures, which are related to the polarization state of the laser pulses, were observed in the cavities. The relationship between the ablation threshold fluence and the number of laser pulses applied to the same spot is described in accordance with an incubation model. T2 - 5th International Conference on Laser Ablation ; COLA '99 CY - Göttingen, Germany DA - 1999-07-19 KW - Polyimide KW - Laser KW - Ablation KW - Femtosecond laser PY - 1999 U6 - https://doi.org/10.1007/s003390051424 SN - 0947-8396 VL - 69 IS - 7 SP - S395 EP - S398 PB - Springer CY - Berlin AN - OPUS4-780 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rudolph, Pascale A1 - Bonse, Jörn A1 - Krüger, Jörg A1 - Kautek, Wolfgang T1 - Femtosecond- and nanosecond-pulse laser ablation of bariumalumoborosilicate glass N2 - Laser ablation with femtosecond pulses (130 fs, wavelength 800 nm, repetition rate 2 Hz) was compared with nanosecond-pulse ablation (10 ns, wavelength 266 nm, repetition rate 2.5 Hz) of bariumalumoborosilicate glass in air using the direct focusing technique. Different ablation thresholds and heat-affected zones were observed. The lateral and vertical machining precision was evaluated. Single nanosecond laser pulses in the far UV resulted in a bubble or a circular hole in the centre of the illuminated spot, depending on the applied fluence. The ablation behaviour in the case of near-IR femtosecond pulses contrasted to this. Bubble formation was not detected. It needed repeated pulses at the same spot to modify the surface until material removal could be observed (incubation). Cavity dimensions of less than the beam diameter were achieved in this case. T2 - 5th International Conference on Laser Ablation ; COLA '99 CY - Göttingen, Germany DA - 1998-07-19 KW - Laser ablation KW - Bariumalumoborosilicate glass PY - 1999 U6 - https://doi.org/10.1007/s003390051524 SN - 0947-8396 VL - 69 IS - 7 SP - S763 EP - S766 PB - Springer CY - Berlin AN - OPUS4-801 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Jörg A1 - Bonse, Jörn A1 - Lenzner, Matthias T1 - Modification and Ablation of Semiconductors by Femtosecond Laser Pulses N2 - Physical and chemical phenomena resulting from irradiation of silicon and indium phosphide with ultrashort laser pulses (~100fs) were investigated with respect to the difference between single- and multiple-pulse treatment. In the single-pulse case, several processes were identified: modification, recrystallization and ablation. All processes exhibit a distinct treshold behaviour. A two photon-absorption coefficient can be determined from a single spatial ablation profile. Accumulation effects were observed for multi-pulse illumination. Different morphological features like bubbles, rippels and microcolumns were found. PY - 2002 VL - 5 IS - 2 SP - 437 EP - 461 PB - Transworld Research Network CY - Trivandrum AN - OPUS4-1585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Wrobel, J. M. A1 - Brzezinka, Klaus-Werner A1 - Esser, N. A1 - Kautek, Wolfgang T1 - Femtosecond laser irradiation of indium phosphide in air: Raman spectroscopic and atomic force microscopic investigations KW - Femtosecond laser ablation KW - Indium phosphide KW - Raman spectroscopy KW - Atomic force microscopy PY - 2002 SN - 0169-4332 SN - 1873-5584 VL - 202 SP - 272 EP - 282 PB - North-Holland CY - Amsterdam AN - OPUS4-2645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Kautek, Wolfgang A1 - Krüger, Jörg A1 - Welsch, E. T1 - Femtosecond laser damage of a high reflecting mirror N2 - Multiple pulse investigations of 130-fs Ti:sapphire laser-induced damage of a high reflecting mirror consisting of alternating ?/4-layers of Ta2O5 and SiO2 and a single 500-nm Ta2O5 film were performed. In both cases, fused silica served as the substrate. For a fixed number of 1000 laser pulses per spot, a decrease in the damage threshold fluence of the mirror by a factor of two was observed by changing the repetition rate from 10 Hz to 1 kHz. A single 500-nm Ta2O5 film shows higher damage resistance compared to the mirror. The mirror and the Ta2O5 film samples were partially coated with a 300-nm-thick aluminium layer. The aluminium coating does not influence the damage threshold of the dielectrics underneath. KW - Aluminium KW - Laser ablation KW - Optical coatings KW - Silicon oxide PY - 2002 U6 - https://doi.org/10.1016/S0040-6090(02)00074-3 SN - 0040-6090 IS - 408 SP - 297 EP - 301 PB - Elsevier CY - Amsterdam AN - OPUS4-1382 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Munz, Martin A1 - Sturm, Heinz T1 - Structure formation on the surface of indium phosphide irradiated by femtosecond laser pulses N2 - Laser-induced periodic surface structures (LIPSS; ripples) with different spatial characteristics have been observed after irradiation of single-crystalline indium phosphide (c-InP) with multiple linearly polarized femtosecond pulses (130 fs, 800 nm) in air. With an increasing number of pulses per spot, N, up to 100, a characteristic evolution of two different types of ripples has been observed, i.e., (i) the growth of a grating perpendicular to the polarization vector consisting of nearly wavelength-sized periodic lines and (ii), in a specific pulse number regime (N = 5–30), the additional formation of equally oriented ripples with a spatial period close to half of the laser wavelength. For pulse numbers higher than 50, the formation of micrometer-spaced grooves has been found, which are oriented perpendicular to the ripples. These topographical surface alterations are discussed in the frame of existing LIPSS theories. KW - Femtosecond laser irradiation KW - Indium phosphide KW - Microstructure KW - Laser induced periodic surface structures KW - LIPSS KW - SEM PY - 2005 U6 - https://doi.org/10.1063/1.1827919 SN - 0021-8979 SN - 1089-7550 VL - 97 SP - 013538-1 EP - 013538-9 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-5992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Krüger, Jörg A1 - Kautek, Wolfgang ED - Exarhos, G. T1 - Femtosecond laser damage in dielectric coatings N2 - Multi-shot investigations of Ti:sapphire laser (wavelength (lambda) approximately equals 800 nm) induced damage were performed in three different laboratories (BAM, Berlin; LZH, Hannover; UNM, Albuquerque). The ablation behavior of a high reflecting mirror consisting of alternating (lambda) /4- layers of Ta2O5 and SiO2 was studied. Fused silica served as substrate. The influence of the pulse duration ((tau) equals 13 - 130 fs), the pulse number (30 - (infinity) ) and the repetition rate (10 Hz - 100 MHz) on the damage threshold will be discussed. T2 - 32nd Annual Boulder Damage Symposium CY - Boulder, CO, USA DA - 2000-10-16 PY - 2001 SN - 0-8194-4036-1 U6 - https://doi.org/10.1117/12.425056 SN - 1605-7422 N1 - Serientitel: SPIE proceedings series – Series title: SPIE proceedings series IS - 4347 SP - 24 EP - 34 PB - International Society for Optical Engineering (SPIE) CY - Bellingham, Wash. AN - OPUS4-6013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seuthe, T. A1 - Grehn, M. A1 - Mermillod-Blondin, A. A1 - Eichler, H.J. A1 - Bonse, Jörn A1 - Eberstein, M. T1 - Structural modifications of binary lithium silicate glasses upon femtosecond laser pulse irradiation probed by micro-Raman spectroscopy N2 - The effects of single femtosecond laser pulse irradiation (130 fs pulse duration, 800 nm center wavelength) on the structure of binary lithium silicate glasses of varying chemical compositions were investigated by micro-Raman spectroscopy. Permanent modifications were generated at the surface of the glass samples with varying laser fluences in the ablative regime and evaluated for changes in the corresponding Raman band positions and bandwidths. For increasing laser fluences, the position of certain Raman bands changed, indicating an increase in the mass density of the glass inside the irradiated area. Simultaneously, the widths of all investigated bands increased, indicating a higher degree of disorder in the glass structure with respect to bond-angle and bond-length variations. PY - 2013 U6 - https://doi.org/10.1364/OME.3.000755 SN - 2159-3930 VL - 3 IS - 6 SP - 755 EP - 764 PB - OSA CY - Washington, DC AN - OPUS4-28372 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grehn, M. A1 - Reinhardt, F. A1 - Bonse, Jörn A1 - Eberstein, M. A1 - Seuthe, T. T1 - Response to "comment on 'femtosecond laser-induced modification of potassium-magnesium silicate glasses: an analysis of structural changes by near edge x-ray absorption spectroscopy'" KW - Bond lengths KW - Glass KW - High-speed optical techniques KW - Magnesium compounds KW - Monochromators KW - Potassium compounds KW - Silicon compounds KW - XANES PY - 2013 U6 - https://doi.org/10.1063/1.4804148 SN - 0003-6951 SN - 1077-3118 VL - 102 SP - 196102-1 - 196102-2 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-28520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Krüger, Jörg A1 - Höhm, S. A1 - Rosenfeld, A. T1 - Femtosecond laser-induced periodic surface structures N2 - The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ~30–150 fs, λ~800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength λ are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (~λ/10) can be generated. For semiconductors, the impact of transient changes of the optical properties to the LIPSS periods is analyzed theoretically and experimentally. In dielectrics, the importance of transient excitation stages in the LIPSS formation is demonstrated experimentally using (multiple) double-fs-laser-pulse irradiation sequences. A characteristic decrease of the LIPSS periods is observed for double-pulse delays of less than 2 ps. KW - Laser-induced periodic surface structures (LIPSS) KW - Femtosecond laser ablation KW - Ultrafast optical techniques KW - Silicon KW - Titanium KW - Silica PY - 2012 U6 - https://doi.org/10.2351/1.4712658 SN - 1042-346X SN - 1938-1387 VL - 24 IS - 4 SP - 042006-1 EP - 042006-7 PB - Laser Institute of America CY - Orlando, Fla., USA AN - OPUS4-26198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Femtosecond laser-induced periodic surface structures on silica N2 - The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused silica glass) upon irradiation in air with multiple linearly polarized single- and double-fs-laser pulse sequences (τ = 150 fs pulse duration, λ = 800nm center wavelength, temporal pulse separation Δt < 40 ps) is studied experimentally and theoretically. Two distinct types of fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL)] with different spatial periods and orientations were identified. Their appearance was characterized with respect to the experimental parameters peak laser fluence and number of laser pulses per spot. Additionally, the 'dynamics' of the LIPSS formation was addressed in complementary double-fs-pulse experiments with varying delays, revealing a characteristic change of the LSFL periods. The experimental results are interpreted on the basis of a Sipe-Drude model considering the carrier dependence of the optical properties of fs-laser excited silica. This new approach provides an explanation of the LSFL orientation parallel to the laser beam polarisation in silica—as opposed to the behaviour of most other materials. KW - High-speed optical techniques KW - Laser beam effects KW - Refractive index KW - Silicon compounds KW - Surface structure PY - 2012 U6 - https://doi.org/10.1063/1.4730902 SN - 0021-8979 SN - 1089-7550 VL - 112 IS - 1 SP - 014901-1 - 014901-9 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26201 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grehn, M. A1 - Tsai, W.J. A1 - Höfner, M. A1 - Seuthe, T. A1 - Bonse, Jörn A1 - Mermillod-Blondin, A. A1 - Rosenfeld, A. A1 - Hennig, J. A1 - Achtstein, A. W. A1 - Theiss, C. A1 - Woggon, U. A1 - Eberstein, M. A1 - Eichler, H.J. T1 - Nonlinear optical properties of binary and ternary silicate glasses upon near-infrared femtosecond pulse laser irradiation N2 - Some nonlinear optical properties such as the nonlinear refractive index and the nonlinear effective absorption, as well as the laser-induced single-pulse ablation threshold are characterized for a series of binary and ternary silicate glasses upon irradiation with near-infrared femtosecond laser pulses (800 nm, 130 fs). The laser-induced ablation threshold varies from 2.3 J/cm² in case of potassium silicate glass up to 4.3 J/cm² in case of Fused Silica. Nonlinear refractive indices are qualitatively similar within the range 1.7-2.7×10-16 cm²/W. Complementary optical and physico-chemical properties like band gap energy and the glass transformation temperature have been measured for all the glasses. T2 - International symposium on high power laser ablation 2012 CY - Santa Fe, NM, USA DA - 30.04.2012 KW - Laser-induced damage threshold KW - Laser ablation KW - Nonlinear refractive index KW - Silicate glass systems KW - Glass transformation temperature KW - Coefficient of thermal expansion PY - 2012 SN - 978-0-7354-1068-8 U6 - https://doi.org/10.1063/1.4739918 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1464 SP - 660 EP - 670 AN - OPUS4-26318 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Area dependence of femtosecond laser-induced periodic surface structures for varying band gap materials after double pulse excitation N2 - The formation of laser-induced periodic surface structures upon irradiation of titanium, silicon, and fused silica with multiple irradiation sequences consisting of parallel polarized Ti:sapphire femtosecond laser pulse pairs (pulse duration 50–150 fs, central wavelength ~800 nm) is studied experimentally. The temporal delay between the individual near-equal energy fs-laser pulses was varied between 0 and 5 ps with a temporal resolution of better than 0.2 ps. The surface morphology of the irradiated surface areas is characterized by means of scanning electron microscopy (SEM). In all materials a decrease of the rippled surface area is observed for increasing delays. The characteristic delay decay scale is quantified and related to material dependent excitation and energy relaxation processes. KW - Laser-induced periodic surface structures (LIPSS) KW - Femtosecond laser ablation KW - Double-pulse experiments KW - Ultrafast optical techniques KW - Mach-Zehnder interferometer PY - 2013 U6 - https://doi.org/10.1016/j.apsusc.2012.10.188 SN - 0169-4332 SN - 1873-5584 VL - 278 SP - 7 EP - 12 PB - North-Holland CY - Amsterdam AN - OPUS4-28601 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Hertwig, Andreas A1 - Koter, Robert A1 - Weise, Matthias A1 - Beck, Uwe A1 - Reinstädt, Philipp A1 - Griepentrog, Michael A1 - Krüger, Jörg A1 - Picquart, M. A1 - Haro-Poniatowski, E. T1 - Femtosecond laser pulse irradiation effects on thin hydrogenated amorphous carbon layers N2 - The irradiation of ~0.9-µm-thick hydrogenated amorphous carbon (a-C:H) layers deposited on silicon substrates with single femtosecond (fs) laser pulses (35 fs pulse duration, 790 nm centre wavelength) in air is studied experimentally. Irradiation spots have been generated with different peak fluences and subsequently investigated by optical topometry, micro Raman spectroscopy and microscale mechanical indentation in order to evaluate their microscopic, topographical, structural and mechanical properties (e.g. elastic modulus). By this multi-method approach, a clear separation of different effects (delamination and graphitisation) becomes possible. The joint application of mechanical and spectroscopic techniques provides unique insights into the effects of the fs-laser radiation on the carbon layer. PY - 2013 U6 - https://doi.org/10.1007/s00339-012-7170-5 SN - 0947-8396 VL - 112 IS - 1 SP - 9 EP - 14 PB - Springer CY - Berlin AN - OPUS4-28629 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Geier, M. A1 - Eberstein, M. A1 - Grießmann, H. A1 - Partsch, U. A1 - Völkel, L. A1 - Böhme, R. A1 - Mann, Guido A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Impact of laser treatment on phosphoric acid coated multicrystalline silicon PV-wafers N2 - The selective emitter is a well-known technology for producing highly doped areas under the metallization grid to improve the solar cell performance. In this work, the influence of laser irradiation on phosphoric acid coated multicrystalline silicon PV-wafers on the wafer surface structure, the phosphorous depth distribution and the electrical contact resistance within the laser treated area as well as the electrical series resistance of laserprocessed solar cells was evaluated. Different laser processing settings were tested including pulsed and continuous wave (cw) laser sources (515 nm, 532 nm, 1064 nm wavelength). Complementary numerical simulations using the finite element method (FEM) were conducted to explain the impact of the laser parameters on the melting behavior (melt duration and geometry). It was found that the melt duration is a key parameter for a successful laser Doping process. Our simulations at a laser wavelengths of 515 nm reveal that low-repetition rate (<500 kHz) laser pulses of 300 ns duration generate a melt duration of ~0.35 µs, whereas upon scanning cw-laser radiation at 532 nm prolongates the melt duration by at least one order of magnitude. Experimentally, the widely used ns-laser pulses did not lead to satisfying laser irradiation results. In contrast, cw-laser radiation and scan velocities of less than 2 m/s led to suitable laser doping featuring low electrical resistances in the laser treated areas. T2 - 26th European photovoltaic solar energy conference and exhibition CY - Hamburg, Germany DA - 05.09.2011 KW - Silicon solar cell KW - Selective emitter KW - Laser processing KW - Doping KW - Simulation PY - 2011 SN - 3-936338-27-2 U6 - https://doi.org/10.4229/26thEUPVSEC2011-2BV.1.7 SP - 1243 EP - 1247 AN - OPUS4-24995 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eberstein, M. A1 - Geier, M. A1 - Grießmann, H. A1 - Partsch, U. A1 - Voelkel, L. A1 - Böhme, R. A1 - Pentzien, Simone A1 - Koter, Robert A1 - Mann, Guido A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Towards an industrial laser doping process for the selective emitter using phosphoric acid as dopant N2 - Different laser supported approaches have already been realized, proving the great potential of laserdoped selective emitters (LDSE). However, it is challenging to establish a low-cost process by using pulsed laser tools. So far a single-step process only leads to satisfying results utilizing cw-lasers. In this paper we have examined a two-step process to produce laser-doped selective emitters on multicrystalline textured standard silicon photovoltaic wafers (90-Ω/sq-Emitter, SiN-antireflection coating (ARC)). The precise ARC removal by near-infrared fs-laser pulses (30 fs, 800 nm), and the doping of uncoated silicon wafers by ns-laser pulses (8 ns, 532 nm) were systematically investigated. In the fs-experiment, optimum conditions for ARC removal were identified. In the nsexperiments under suitable conditions (melting regime), the phosphorous concentration underneath the wafer surface was significantly increased and the sheet resistance was reduced by nearly a factor of two. Moreover, electrical measurements on fired metallization fingers deposited on the laser processed wafers showed low contact resistances. Hence, wafer conditioning with combined fs-laser- and ns-laser-processes are expected to be a promising technology for producing selective emitters. T2 - 26th European photovoltaic solar energy conference and exhibition CY - Hamburg, Germany DA - 05.09.2011 KW - Laser processing KW - Doping KW - Selective emitter KW - Multicrystalline silicon PY - 2011 SN - 3-936338-27-2 U6 - https://doi.org/10.4229/26thEUPVSEC2011-2BV.1.2 SP - 1220 EP - 1223 AN - OPUS4-24996 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, M. A1 - Schultz, C. A1 - Bonse, Jörn A1 - Pahl, H.-U. A1 - Endert, H. A1 - Rau, B. A1 - Schlatmann, R. A1 - Quaschning, V. A1 - Stegemann, B. A1 - Fink, F. T1 - Laser-ablation behavior of thin-film materials used in silicon and CIGSe based solar cells N2 - Structuring of thin-film photovoltaic modules requires basic knowledge of the laser – thin-film interaction in order to adapt the accessible laser parameters, like wavelength, power, repetition rate and scribing speed whilst taking into account the specific material properties of the layer. We have studied the nanosecond laserablation behavior of corresponding layers (i) of silicon based thin-film solar cells with a-Si/µc-Si tandem absorber type and (ii) of back contact and absorber layer of CIGSe solar cells. The respective ablation threshold fluences were determined as integrative parameters describing the specific laser – material interaction. For the threshold determination we used two different methods and developed a new analytical approach taking into account scribing through the glass substrate as it is preferred for most structuring processes. This was done by analyzing the thin film ablation results by means of optical microscopy, profilometry, scanning electron microscopy (SEM). Moreover, we determined the incubation coefficient of the regarded material layers which allows us to predict quantitatively the influence of the spot overlap on the scribing threshold. T2 - 26th European photovoltaic solar energy conference and exhibition CY - Hamburg, Germany DA - 05.09.011 KW - Laser processing KW - Ablation KW - Incubation KW - a-Si/my-Si KW - CIGS PY - 2011 SN - 3-936338-27-2 U6 - https://doi.org/10.4229/26thEUPVSEC2011-3DV.2.8 SP - 2943 EP - 2946 AN - OPUS4-24997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schultz, C. A1 - Schüle, M. A1 - Richter, M. A1 - Pahl, H.-U. A1 - Endert, H. A1 - Bonse, Jörn A1 - Dirnstorfer, I. A1 - Rau, B. A1 - Schlatmann, R. A1 - Quaschning, V. A1 - Fink, F. A1 - Stegemann, B. T1 - P1, P2 and P3 structuring of CIGSe solar cells with a single laser wavelength N2 - Manufacturing of CIGSe thin film solar modules involves typically one laser structuring step (P1) and two mechanical structuring steps (P2 and P3) for serial interconnection. In our approach, complete laser structuring is successfully demonstrated by application of short nanosecond laser pulses (<10 ns) with a single, visible wavelength of 532 nm. The P1 and the P3 trenches are scribed by induced and direct ablation, respectively. For the P2 scribe, the thermal input of the ns laser pulses is used to transform the CIGSe absorber layer locally into a highly conductive compound to provide proper electrical interconnection. These findings promise further simplification and flexibility to thin film solar cell production. T2 - 26th European photovoltaic solar energy conference and exhibition CY - Hamburg, Germany DA - 05.09.2011 KW - Laser processing KW - Nanosecond pulses KW - Ablation KW - Cu(InGa)Se2 KW - Electrical properties PY - 2011 SN - 3-936338-27-2 U6 - https://doi.org/10.4229/26thEUPVSEC2011-3AV.1.35 SP - 2540 EP - 2543 AN - OPUS4-24998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Femtosecond diffraction dynamics of laser-induced periodic surface structures on fused silica N2 - The formation of laser-induced periodic surface structures (LIPSS) on fused silica upon irradiation with linearly polarized fs-laser pulses (50 fs pulse duration, 800?nm center wavelength) is studied experimentally using a transillumination femtosecond time-resolved (0.1 ps-1 ns) pump-probe diffraction approach. This allows to reveal the generation dynamics of near-wavelength-sized LIPSS showing a transient diffraction at specific spatial frequencies even before a corresponding permanent surface relief was observed. The results confirm that the ultrafast energy deposition to the materials surface plays a key role and triggers subsequent physical mechanisms such as carrier scattering into self-trapped excitons. KW - High-speed optical techniques KW - Laser beam effects KW - Silicon compounds KW - Surface structure PY - 2013 U6 - https://doi.org/10.1063/1.4790284 SN - 0003-6951 SN - 1077-3118 VL - 102 IS - 5 SP - 054102-1 EP - 054102-4 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-27646 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Beke, S. A1 - Sugioka, K. A1 - Midorikawa, K. A1 - Bonse, Jörn ED - Hemsworth, E.J. T1 - Nanaosecond and femtosecond laser ablation of TeO2 crystals: surface characterization and plasma analysis N2 - Near-IR femtosecond (fs) (pulse duration = 150 fs, wavelength = 775 nm, repetition rate 1 kHz) and VUV nanosecond (ns) (pulse duration = 20 ns, wavelength = 157 nm, repetition rate 1 to 5 Hz) laser pulse ablation of single-crystalline TeO2 (c-TeO2 ) surfaces was performed in air using the direct focusing technique. A multi-method characterization using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters. This allowed us at each irradiation site to characterize precisely the lateral and vertical dimensions of the laser-ablated craters for different laser pulse energies and number of laser pulses per spot. Based on the obtained information, we quantitatively determined the ablation threshold fluence for the fs laser irradiation when different pulse numbers were applied to the same spot using two independent extrapolation techniques. We found that in the case of NIR fs laser pulse irradiation, the ablation threshold significantly depends on the number of laser pulses applied to the same spot indicating that incubation effects play an important role in this material. In the case of VUV ns laser pulses, the ablation rate is significantly higher due to the high photon energy and the predominantly linear absorption in the material. These results are discussed on the basis of recent models of the interaction of laser pulses with dielectrics. In the second part of this chapter, we use time- of-flight mass spectrometry (TOFMS) to analyze the elemental composition of the ablation products generated upon laser irradiation of c-TeO2 with single fs- (pulse duration ~200 fs, wavelength 398 nm) and ns-pulses (pulse duration 4 ns, wavelength 355 nm). Due to the three order of magnitude different peak intensities of the ns- and fs laser pulses, significant differences were observed regarding the laser-induced species in the plasma plume. Positive singly, doubly and triply charged Te ions (Te+, Te2+, Te3+) in the form of many different isotopes were observed in case of both irradiations. In the case of the ns-laser ablation, the TeO+ formation was negligible compared to the fs case and there was no Te trimer (Te3+) formation observed. It was found that the amplitude of Te ion signals strongly depends on the applied laser pulse energy. Singly charged oxygen ions (O+) are always present as a byproduct in both kinds of laser ablation. KW - Tellurium dioxide crystals KW - Femtosecond laser ablation KW - VUV nanosecond laser ablation KW - Multiphoton absorption KW - Time-of-flight mass spectroscopy KW - Incubation KW - Optical properties KW - Scanning electron microscopy KW - Atomic force microscopy KW - Isotopes PY - 2011 SN - 978-1-61324-851-5 N1 - Serientitel: Physics Research and Technology – Series title: Physics Research and Technology IS - Chapter 4 SP - 77 EP - 96 PB - Nova Science Publishers, Inc. AN - OPUS4-25454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seuthe, T. A1 - Höfner, M. A1 - Reinhardt, F. A1 - Tsai, W.J. A1 - Bonse, Jörn A1 - Eberstein, M. A1 - Eichler, H.J. A1 - Grehn, M. T1 - Femtosecond laser-induced modification of potassium-magnesium silicate glasses: An analysis of structural changes by near edge x-ray absorption spectroscopy N2 - The effects of femtosecond laser pulse irradiation on the glass structure of alkaline silicate glasses were investigated by x-ray absorption near edge structure spectroscopy using the beamline of the Physikalisch-Technische Bundesanstalt at the electron synchrotron BESSY II in Berlin (Germany) by analyzing the magnesium Κ-edge absorption peak for different laser fluences. The application of fluences above the material modification threshold (2.1 J/cm²) leads to a characteristic shift of ~1.0 eV in the Κ-edge revealing a reduced (~3%) mean magnesium bond length to the ligated oxygen ions (Mg-O) along with a reduced average coordination number of the Mg ions. KW - Glass KW - Glass structure KW - Laser beam effects KW - Magnesium compounds KW - Potassium compounds KW - XANES PY - 2012 U6 - https://doi.org/10.1063/1.4723718 SN - 0003-6951 SN - 1077-3118 VL - 100 IS - 22 SP - 224101-1 EP - 224101-3 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-25918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosenfeld, A. A1 - Rohloff, M. A1 - Höhm, S. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Formation of laser-induced periodic surface structures on fused silica upon multiple parallel polarized double-femtosecond-laser-pulse irradiation sequences N2 - The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences of parallel polarized Ti:sapphire femtosecond laser pulse pairs (160 fs pulse duration, 800 nm central wavelength) was studied experimentally. For that purpose, a Michelson interferometer was used to generate near-equal-energy double-pulse sequences allowing the temporal pulse delay between the parallel-polarized individual fs-laser pulses to be varied between 0 and 40 ps with ~0.2 ps temporal resolution. The surface morphologies of the irradiated surface areas were characterized by means of scanning electron and scanning force microscopy. In the sub-ps delay range a strong decrease of the LIPSS periods and the ablation crater depths with the double-pulse delay was observed indicating the importance of the laser-induced free-electron plasma in the conduction band of the solids for the formation of LIPSS. KW - Laser-induced periodic surface structures (LIPSS) KW - Femtosecond laser ablation KW - Double-pulse experiments KW - Fused silica KW - Michelson interferometer PY - 2012 U6 - https://doi.org/10.1016/j.apsusc.2011.09.076 SN - 0169-4332 SN - 1873-5584 VL - 258 IS - 23 SP - 9233 EP - 9236 PB - North-Holland CY - Amsterdam AN - OPUS4-26226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhm, S. A1 - Rohloff, M. A1 - Rosenfeld, A. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Dynamics of the formation of laser-induced periodic surface structures on dielectrics and semiconductors upon femtosecond laser pulse irradiation sequences N2 - The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica and silicon with multiple (NDPS) irradiation sequences consisting of linearly polarized femtosecond laser pulse pairs (pulse duration ~150 fs, central wavelength ~800 nm) is studied experimentally. Nearly equal-energy double-pulse sequences are generated allowing the temporal pulse delay Δt between the cross-polarized individual fs-laser pulses to be varied from -40 ps to +40 ps with a resolution of ~0.2 ps. The surface morphologies of the irradiated surface areas are characterized by means of scanning electron and scanning force microscopy. Particularly for dielectrics in the sub-ps delay range striking differences in the orientation and spatial characteristics of the LIPSS can be observed. For fused silica, a significant decrease of the LIPSS spatial periods from ~790 nm towards ~550 nm is demonstrated for delay changes of less than ~2 ps. In contrast, for silicon under similar irradiation conditions, the LIPSS periods remain constant (~760 nm) for delays up to 40 ps. The results prove the impact of laser-induced electrons in the conduction band of the solid and associated transient changes of the optical properties on fs-LIPSS formation. PY - 2013 U6 - https://doi.org/10.1007/s00339-012-7184-z SN - 0947-8396 VL - 110 IS - 3 SP - 553 EP - 557 PB - Springer CY - Berlin AN - OPUS4-27787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg T1 - Sub-100-nm laser-induced periodic surface structures upon irradiation of titanium by Ti:sapphire femtosecond laser pulses in air N2 - The formation of laser-induced periodic surface structures (LIPSS) on titanium upon irradiation with linearly polarized femtosecond (fs) laser pulses (τ = 30 fs, λ = 790 nm) in an air environment is studied experimentally and theoretically. In the experiments, the dependence on the laser fluence and the number of laser pulses per irradiation spot has been analyzed. For a moderate number of laser pulses (N < 1000) and at fluences between ~0.09 and ~0.35 J/cm², predominantly low-spatial-frequency-LIPSS with periods between 400 nm and 800 nm are observed perpendicular to the polarization. In a narrow fluence range between 0.05 and 0.09 J/cm², high-spatial-frequency-LIPSS with sub-100-nm spatial periods (~λ/10) can be generated with an orientation parallel to the polarization (N = 50). These experimental results are complemented by calculations based on a theoretical LIPSS model and compared to the present literature. PY - 2013 U6 - https://doi.org/10.1007/s00339-012-7140-y SN - 0947-8396 VL - 110 IS - 3 SP - 547 EP - 551 PB - Springer CY - Berlin AN - OPUS4-27788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Krüger, Jörg A1 - Kautek, Wolfgang A1 - Lenzner, Matthias T1 - Femtosecond laser ablation of silicon-modification thresholds and morphology N2 - We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization, nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed new morphological features (bubbles) as well as familiar ones (ripples, columns). A nearly constant ablation threshold fluence on the order of 0.2 J/cm2 for all pulse durations and multiple-pulse irradiation was observed. For a duration of ,100 fs, significant incubation can be observed, whereas for 5 fs pulses, the ablation threshold does not depend on the pulse number within the experimental error. For micromachining of silicon, a pulse duration of less than 500 fs is not advantageous. PY - 2002 U6 - https://doi.org/10.1007/s003390100893 SN - 0947-8396 VL - 74 IS - 1 SP - 19 EP - 25 PB - Springer CY - Berlin AN - OPUS4-6328 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jeschke, H.O. A1 - Garcia, M.E. A1 - Lenzner, Matthias A1 - Bonse, Jörn A1 - Krüger, Jörg A1 - Kautek, Wolfgang T1 - Laser ablation thresholds of silicon for different pulse durations: theory and experiment N2 - The ultrafast laser ablation of silicon has been investigated experimentally and theoretically. The theoretical description is based on molecular dynamics (MD) simulations combined with a microscopic electronic model. We determine the thresholds of melting and ablation for two different pulse durations =20 and 500 fs. Experiments have been performed using 100 Ti:Sap-phire laser pulses per spot in air environment. The ablation thresholds were determined for pulses with a duration of 25 and 400 fs, respectively. Good agreement is obtained between theory and experiment. KW - Laser ablation KW - Pulse duration KW - Threshold of silicon PY - 2002 U6 - https://doi.org/10.1016/S0169-4332(02)00458-0 SN - 0169-4332 SN - 1873-5584 VL - 197-198 SP - 839 EP - 844 PB - North-Holland CY - Amsterdam AN - OPUS4-6314 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Munz, Martin A1 - Sturm, Heinz T1 - Scanning force microscopic investigations of the femtosecond laser pulse irradiation of indium phosphide in air N2 - Laser ablation of single-crystalline indium phosphide (InP) was performed in air by means of linearly polarized Ti : sapphire femtosecond pulses (800 nm, 130 fs, 10 Hz). As a result of the irradiation with a variable number of laser pulses per spot (N /spl les/ 5), several morphological changes (crater formation, rim formation, ripple structures, and cones) were observed. These effects were explored using force modulation microscopy (FMM), a technique based on scanning force microscopy, allowing the simultaneous imaging of both topography and local stiffness at a high lateral resolution. The first laser pulse induces the formation of a protruding rim (height < 20 nm, width /spl ap/ 300 nm) bordering the ablated crater. A Fourier analysis of the multipulse generated topographies reveals the formation of wavelength-sized periodic ripples (modulation depth < 100 nm) with an orientation perpendicular to that of the electric field vector of the laser radiation. Besides these morphological alterations, material modifications were also observed in the irradiated regions by means of the FMM technique. Within the ablated craters, local stiffness variations were found revealing an inhomogeneous material composition/structure as a consequence of the femtosecond pulse laser treatment. KW - Laser materials-processing applications KW - Laser radiation effects KW - Microscopy KW - Semiconductor materials KW - Ultrafast optics PY - 2004 U6 - https://doi.org/10.1109/TNANO.2004.828574 SN - 1536-125X SN - 1941-0085 VL - 3 IS - 3 SP - 358 EP - 367 PB - Institute of Electrical and Electronics Engineers CY - New York, NY AN - OPUS4-4067 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Bachelier, G. A1 - Siegel, J. A1 - Solis, J. A1 - Sturm, Heinz T1 - Time- and space-resolved dynamics of ablation and optical breakdown induced by femtosecond laser pulses in indium phosphide N2 - Femtosecond time-resolved microscopy has been used to analyze the structural transformation dynamics (melting, ablation, and solidification phenomena) induced by single intense 130 fs laser pulses in single-crystalline (100)-indium phosphide wafers in air on a time scale from ~100 fs up to 8 ns. In the ablative regime close to the ablation threshold, transient surface reflectivity patterns are observed by fs microscopy on a ps to ns time scale as a consequence of the complex spatial density structure of the ablating material (dynamic Newton fringes). At higher fluences, exceeding six times the ablation threshold, optical breakdown causes another, more violent ablation regime, which reduces the energy deposition depth along with the time of significant material removal. As a consequence, ablation lasts longer in a ring-shaped region around the region of optical breakdown. This leads to the formation of a crater profile with a central protrusion. In the melting regime below the ablation threshold, the melting dynamics of indium phosphide has been quantified and subsequent superficial amorphization has been observed upon solidification on the ns time scale leading to amorphous layer thicknesses of the order of a few tens of nanometers. KW - Femtosecond laser pulse KW - Indium Phosphide KW - Ablation KW - Surface reflectivity KW - Fs-time resolved microscopy KW - Scanning Force Microscopy PY - 2008 U6 - https://doi.org/10.1063/1.2885105 SN - 0021-8979 SN - 1089-7550 VL - 103 IS - 5 SP - 054910-1 EP - 054910-6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-17090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bonse, Jörn A1 - Munz, Martin A1 - Sturm, Heinz T1 - Scanning force microscopic investigations of the femtosecond pulse laser ablation of indium phosphide in air T2 - SPIE conference Nanotechnology Gran Canaria CY - Maspalomas, Spain DA - 2003-05-20 PY - 2003 AN - OPUS4-4081 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dorronsoro, C. A1 - Bonse, Jörn A1 - Siegel, J. T1 - Self-assembly of a new type of periodic surface structure in a copolymer by excimer laser irradiation above the ablation threshold N2 - We report self-assembly of periodic surface structures in a commercial block copolymer (BCP) (Filofocon A) upon irradiation with a few tens of excimer laser pulses (20 ns, 193 nm) at fluences above the ablation threshold. This new type of structures is characterized by much larger periods than those characteristic for Laser-Induced Periodic Surface Structures (LIPSS) and features nanochains instead of ripples. We find a period of 790?nm at 400 mJ/cm², scaling linearly with laser fluence up to a maximum of 1.0 µm. While an entangled random network of nanochains is produced for normal-incidence and non-polarized light, nanochain alignment can be achieved either by irradiation at an angle or by using linearly polarized light, forming a lamella-like structure. In both cases, the nanochains are aligned parallel to the penetrating polarization orientation and their period does not show a dependence on the angle of incidence, as opposed to the general behavior of standard LIPSS. Also, our results show that the chains are not formed by frozen capillary waves. In contrast, we show analogies of the nanochains produced to lamellar structures fabricated on a smaller scale in other BCP. We discuss the origin of the self-assembly process in terms of a combination of chemical (BCP), optical (surface scattering), and thermal (melting, coarsening, and ablation) effects. PY - 2013 UR - http://scitation.aip.org/content/aip/journal/jap/114/15/10.1063/1.4825128 U6 - https://doi.org/10.1063/1.4825128 SN - 0021-8979 SN - 1089-7550 VL - 114 SP - 153105-1 - 153105-7 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-29395 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Seuthe, T. A1 - Grehn, M. A1 - Mermillod-Blondin, A. A1 - Bonse, Jörn A1 - Eberstein, M. T1 - Compositional dependent response of silica-based glasses after femtosecond laser pulse irradiation N2 - Femtosecond laser pulse irradiation of inorganic glasses allows a selective modification of the optical properties with very high precision. This results in the possibility for the production of three-dimensional functional optical elements in the interior of glass materials, such as optical data storage, waveguide writing, etc. The influence of the chemical glass composition to the response upon ultrashort laser irradiation has not been studied systematically. For that, simple silicabased model glasses composed of systematically varying alkaline- and earth-alkaline components were prepared, irradiated on the surface and in the volume with single fs-laser pulses (~130 fs, 800 nm), and were subsequently analyzed by means of micro-Raman spectroscopy and quantitative phase contrast microscopy in order to account for changes in the glass structure and for alterations of the optical refractive index, respectively. The Raman spectroscopic studies of the laser-irradiated spots revealed no change in the average binding configuration (the so called Q-structure), but local changes of bond-angles and bond-lengths within the glass structure structure. Those changes are explained by structural relaxation of the glass network due to densification caused by a transient laser-induced plasma generation and the following shock wave and other thermal phenomena. Glasses with a low amount of network modifiers show changes in the Si-O network while glasses with a high amount of network modifiers react primarily via variation of the nonbridging oxygen ions. The results are discussed in terms of possible structural response mechanisms and conclusions are outlined regarding glass compositions with technical suitability for fs-laser modifications. T2 - Laser-induced damage in optical materials CY - Boulder, Colorado, USA DA - 2013-09-22 KW - Femtosecond laser modifications KW - Raman spectroscopy KW - Glass KW - Femtosecond phenomena KW - Networks KW - Silica KW - Laser irradiation KW - Lasers KW - Micro raman spectroscopy KW - Microscopy KW - Optical components KW - Optical storage PY - 2013 U6 - https://doi.org/10.1117/12.2028713 N1 - Serientitel: SPIE proceedings series – Series title: SPIE proceedings series VL - 8885 SP - 1 EP - 8(?) AN - OPUS4-29539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grehn, M. A1 - Seuthe, T. A1 - Tsai, W.-J. A1 - Höfner, M. A1 - Achtstein, A. W. A1 - Mermillod-Blondin, A. A1 - Eberstein, M. A1 - Eichler, H.J. A1 - Bonse, Jörn T1 - Nonlinear absorption and refraction of binary and ternary alkaline and alkaline earth silicate glasses N2 - Nonlinear optical properties such as the nonlinear refractive index and nonlinear absorption are characterized by z-scan measurements for a series of silicate glasses upon irradiation with laser pulses of 130 fs duration and 800 nm center wavelength. The stoichiometry of the silicate glasses is varied systematically to reveal the influence of the glass composition on the nonlinear optical properties. Additionally, the thermal properties such as glass–transformation temperature and thermal expansion coefficient are obtained from dilatometric measurements. It is found that the nonlinear refractive index is mainly related to the silica matrix. The nonlinear absorption is increased with the addition of network–forming ions. PY - 2013 U6 - https://doi.org/10.1364/OME.3.002132 SN - 2159-3930 VL - 3 IS - 12 SP - 2132 EP - 2140 PB - OSA CY - Washington, DC AN - OPUS4-29649 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Derrien, Thibault A1 - Krüger, Jörg A1 - Itina, T.E. A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Bonse, Jörn T1 - Rippled area formed by surface plasmon polaritons upon femtosecond laser double-pulse irradiation of silicon N2 - The formation of near-wavelength laser-induced periodic surface structures (LIPSS) on silicon upon irradiation with sequences of Ti:sapphire femtosecond laser pulse pairs (pulse duration 150 fs, central wavelength 800 nm) is studied theoretically. For this purpose, the nonlinear generation of conduction band electrons in silicon and their relaxation is numerically calculated using a two-temperature model approach including intrapulse changes of optical properties, transport, diffusion and recombination effects. Following the idea that surface plasmon polaritons (SPP) can be excited when the material turns from semiconducting to metallic state, the 'SPP active area' is calculated as function of fluence and double-pulse delay up to several picoseconds and compared to the experimentally observed rippled surface areas. Evidence is presented that multi-photon absorption explains the large increase of the rippled area for temporally overlapping pulses. For longer double-pulse delays, relevant relaxation processes are identified. The results demonstrate that femtosecond LIPSS on silicon are caused by the excitation of SPP and can be controlled by temporal pulse shaping. PY - 2013 U6 - https://doi.org/10.1364/OE.21.029643 SN - 1094-4087 VL - 21 IS - 24 SP - 29643 EP - 29655 PB - Optical Society of America CY - Washington, DC AN - OPUS4-29650 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Rosenfeld, A. A1 - Krüger, Jörg T1 - On the role of surface plasmon polaritons in the formation of laser-induced periodic surface structures upon irradiation of silicon by femtosecond-laser pulses N2 - The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSSs) on single-crystalline silicon upon irradiation with single or multiple femtosecond-laser pulses (pulse duration τ=130 fs and central wavelength λ=800 nm) in air is studied experimentally and theoretically. In our theoretical approach, we model the LIPSS formation by combining the generally accepted first-principles theory of Sipe and co-workers with a Drude model in order to account for transient intrapulse changes in the optical properties of the material due to the excitation of a dense electron-hole plasma. Our results are capable to explain quantitatively the spatial periods of the LIPSSs being somewhat smaller than the laser wavelength, their orientation perpendicular to the laser beam polarization, and their characteristic fluence dependence. Moreover, evidence is presented that surface plasmon polaritons play a dominant role during the initial stage of near-wavelength-sized periodic surface structures in femtosecond-laser irradiated silicon, and it is demonstrated that these LIPSSs can be formed in silicon upon irradiation by single femtosecond-laser pulses. KW - Ab initio calculations KW - Elemental semiconductors KW - High-speed optical techniques KW - Laser beam effects KW - Polaritons KW - Silicon KW - Solid-state plasma KW - Surface plasmons KW - Surface structure PY - 2009 U6 - https://doi.org/10.1063/1.3261734 SN - 0021-8979 SN - 1089-7550 VL - 106 IS - 10 SP - 104910-1 - 104910-5 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-20453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Pulse number dependence of laser-induced periodic surface structures for femtosecond laser irradiation of silicon N2 - The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSS) on single-crystalline silicon upon irradiation with single (N = 1) and multiple (N ≤ 1000) linearly polarized femtosecond (fs) laser pulses (pulse duration τ = 130 fs, central wavelength λ = 800 nm) in air is studied experimentally. Scanning electron microscopy (SEM) and optical microscopy are used for imaging of the ablated surface morphologies, both revealing LIPSS with periodicities close to the laser wavelength and an orientation always perpendicular to the polarization of the fs-laser beam. It is experimentally demonstrated that these LIPSS can be formed in silicon upon irradiation by single fs-laser pulses—a result that is additionally supported by a recent theoretical model. Two-dimensional Fourier transforms of the SEM images allow the detailed analysis of the distribution of the spatial frequencies of the LIPSS and indicate, at a fixed peak fluence, a monotonous decrease in their mean spatial period between ~770 nm (N = 1) and 560 nm (N = 1000). The characteristic decrease in the LIPSS period is caused by a feedback-mechanism acting upon excitation of surface plasmon polaritons at the rough silicon surface which is developing under the action of multiple pulses into a periodically corrugated surface. KW - Elemental semiconductors KW - Fourier transforms KW - Laser beam effects KW - Optical microscopy KW - Polarisation KW - Polaritons KW - Scanning electron microscopy KW - Silicon KW - Surface morphology KW - Surface plasmons PY - 2010 UR - http://jap.aip.org/resource/1/japiau/v108/i3/p034903_s1 U6 - https://doi.org/10.1063/1.3456501 SN - 0021-8979 SN - 1089-7550 VL - 108 IS - 3 SP - 034903-1 - 034903-5 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-21804 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - Beke, S. A1 - Sugioka, K. A1 - Midorikawa, K. A1 - Bonse, Jörn T1 - Near-IR femtosecond and VUV nanosecond laser processing of TeO2 crystals in air N2 - Near-IR femtosecond ( τ = 150 fs, λ = 775 nm, repetition rate 1 kHz) and VUV nanosecond (τ = 20 ns, λ = 157 nm, repetition rate 1 to 5 Hz) laser pulse ablation of single-crystalline TeO2 (c-TeO2, grown by the balance controlled Czochalski growth method) surfaces was performed in air using the direct focusing technique. The multi-method characterization using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters. This allowed us to characterize precisely the lateral and vertical dimensions of the laser-ablated craters for different laser pulse energies and pulse numbers at each spot. Based on the obtained information, we quantitatively determined the ablation threshold fluence for the fs laser irradiation when different pulse numbers were applied to the same spot by using two independent extrapolation techniques. We found that in case of NIR femtosecond laser pulse irradiation, the ablation threshold significantly depends on the number of laser pulses applied to the same spot indicating that incubation effects play an important role in this material. In case of VUV ns laser pulses, the ablation rate is significantly higher due to the high photon energy and the predominantly linear absorption in the material. These results are discussed on the basis of recent models of the interaction of laser pulses with dielectrics. PY - 2010 U6 - https://doi.org/10.1117/12.845074 SN - 0277-786X SN - 0038-7355 SN - 0361-0748 VL - 7584 SP - 758415-1 - 758415-10 PB - Soc. CY - Redondo Beach, Calif. [u.a.] AN - OPUS4-20912 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 - CONF A1 - Schultz, C. A1 - Schüle, M. A1 - Stelmaszczyk, K. A1 - Bonse, Jörn A1 - Witteck, R. A1 - Weizman, M. A1 - Rhein, H. A1 - Rau, B. A1 - Schlatmann, R. A1 - Quaschning, V. A1 - Stegemann, B. A1 - Fink, F. T1 - Film side laser patterning of molybdenum thin films sputter-deposited onto glass N2 - Serial interconnection of CIGSe thin film solar modules involves typically glass-side laser patterning of the molybdenum layer (P1 scribe). In this paper we present a working principle of P1 film side patterning. The investigated samples were sputter-deposited onto soda-lime glass substrates. For understanding the fundamental ablation behavior, two kinds of layer systems were studied: on the one hand monolayer systems which are compressively stressed and on the other hand bilayer systems, consisting of a tensile stressed layer on the substrate and a second layer on top. The film-side ablation process was studied using a nanosecond as well as a picosecond laser source. The influence of intrinsic stress was studied by XRD. Time resolved spectroscopy reveals the formation of plasma as important driving mechanism for ablation. It is shown that by proper adaption of the sputter conditions high-quality P1 film side patterning is achieved. T2 - 27th European photovoltaic solar energy conference and exhibition CY - Frankfurt, Germany DA - 24.09.2012 KW - Laser processing KW - Molybdenum KW - Strain KW - Ablation KW - Sputter deposition KW - Cu(InGa)Se2 PY - 2012 SN - 3-936338-28-0 U6 - https://doi.org/10.4229/27thEUPVSEC2012-3CV.1.6 SP - 2266 EP - 2272 AN - OPUS4-27208 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -