Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (68)
- Posterpräsentation (31)
- Beitrag zu einem Tagungsband (21)
- Zeitschriftenartikel (13)
- Buchkapitel (10)
- Beitrag zu einem Sammelband (4)
- Monografie (1)
- Corrigendum (1)
- Video (1)
Referierte Publikation
- nein (150) (entfernen)
Schlagworte
Organisationseinheit der BAM
- 6 Materialchemie (58)
- 6.2 Material- und Oberflächentechnologien (58)
- 9 Komponentensicherheit (11)
- 9.5 Tribologie und Verschleißschutz (11)
- 6.1 Oberflächen- und Dünnschichtanalyse (7)
- 4 Material und Umwelt (5)
- 4.1 Biologische Materialschädigung und Referenzorganismen (5)
- 6.6 Physik und chemische Analytik der Polymere (1)
A promising technology in photovoltaics is based on micro-concentrator solar cells, where the photovoltaic active area is realized as an array of sub-millimeter sized cells onto which the incident light is focused via microlenses. This approach allows to increase the cell efficiency and to realize much more compact modules compared to macroscopic concentrator devices. At the same time, expensive raw materials can be saved, which is of interest, for example, with respect to indium in the case of copper-indium-gallium-diselenide (CIGSe) thin film solar cells. Two methods to produce micro-sized precursors of CIGSe absorbers on molybdenum are presented using 30-fs laser pulses at 790 nm wavelength. On the one hand, a multi pulse surface structuring of the molybdenum film or the underlying glass substrate and a subsequent physical vapor deposition were used for a site-selective aggregation of indium droplets. On the other hand, a single pulse laser-induced forward transfer was utilized to selectively deposit combined copper-indium precursor pixels on the molybdenum back contact of the solar cell. Post-processing (selenization, isolation, contacting) of the laser-generated micro-sized precursors results in functional CIGSe solar cells.
The performance of titanium alloy (Ti6Al4V) surfaces was investigated in lubricated reciprocating sliding tribological tests (RSTT). Special emphasis was laid on the effect of surface nanostructures in area of contact on the respective friction and wear behaviour. These so-called laser-induced periodic surface structures (LIPSS, ripples) were produced on the titanium alloy surface upon scan processing in air by an ultrashort pulsed femtosecond (fs) laser. As lubricant served two types of base oils, a pure polyalcylene-glycol, and an SAE 0W30 oil containing only antioxidants and temperature stabilizers. Tribological tests were carried out on polished as well as LIPSS covered areas using both types of base oil. A test metrics was established, combining the additive 2-ethylhexyl-zincdithiophosphate (ZDDP) or the ionic liquid [P6,6,6,14] [DEHP] (98% purity) with the respective base oils. The test metrics also considered the orientation of motion with respect to the orientation of the structures formed on the surface. Results are presented which show that the interplay between LIPSS and the local chemistry formed by the respective additives is beneficial for the tribological behaviour of the titanium alloy. Certain combinations of base oil, additive and LIPSS reduced friction and wear significantly in the tribological contact.
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.
Near-IR femtosecond (fs) (pulse duration = 150 fs, wavelength = 775 um, 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 TeO? (c-Te02) 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 timeof-flight mass spectrometry (TOFMS) to analyze the elemental composltion of the ablation products generated upon laser irradiation of c-Te02 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 (0+) are always present as a byproduct in both kinds of laser ablation.
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.