Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (59)
- Vortrag (36)
- Posterpräsentation (14)
- Beitrag zu einem Tagungsband (11)
- Beitrag zu einem Sammelband (3)
- Newsletter (1)
- Sonstiges (1)
- Forschungsdatensatz (1)
Schlagworte
- Ellipsometry (17)
- Spectroscopic ellipsometry (9)
- Ellipsometrie (5)
- Thin films (5)
- Gas sensing (4)
- Laser-induced periodic surface structures (LIPSS) (4)
- Optical properties (4)
- Spectroscopic Ellipsometry (4)
- Thin Films (4)
- Electrolysis (3)
Organisationseinheit der BAM
- 6 Materialchemie (40)
- 6.1 Oberflächen- und Dünnschichtanalyse (27)
- 6.7 Materialsynthese und Design (17)
- 6.2 Material- und Oberflächentechnologien (7)
- 6.6 Physik und chemische Analytik der Polymere (6)
- 3 Gefahrgutumschließungen; Energiespeicher (2)
- 3.2 Gefahrguttanks und Unfallmechanik (2)
- 4 Material und Umwelt (1)
- 4.1 Biologische Materialschädigung und Referenzorganismen (1)
- 5 Werkstofftechnik (1)
- 5.1 Mikrostruktur Design und Degradation (1)
- 6.0 Abteilungsleitung und andere (1)
- 9 Komponentensicherheit (1)
- 9.5 Tribologie und Verschleißschutz (1)
Paper des Monats
- ja (2)
Visualization of surface modifications may be very challenging for coating/substrate systems of either almost identical optical constants, e.g. transparent films on substrates of the same material, or minor film thickness, substance quantity and affected area, e.g. ultra-thin or island films. Methods for visualization are optical microscopy (OM), imaging ellipsometry (IE), and referenced spectroscopic ellipsometry (RSE). Imaging ellipsometry operates at oblique incidence near Brewster angle of the bare, clean or unmodified substrate. In this configuration, reflected intensities are rather weak. However, the contrast to add-on and sub-off features may be superior. Referenced spectroscopic ellipsometry operates in a two-sample configuration but with much higher intensities. In many cases, both ellipsometric techniques reveal and visualize thin films, printed-pattern, laser-induced changes, and impurities better than optical microscopy. In particular for stratified homogeneous modifications, ellipsometric techniques give access to modelling and hence thickness determination. Modifications under investigation are polymer foil residue on silicon, laser-induced changes of ta-C:H coatings on 100Cr6 steel, imperfections of ta-C:H on thermal silicon oxide, degradation of glass, thin film tin oxide pattern on silicon, printed and dried pattern of liquids such as deionized water, cleaning agents, and dissolved silicone. © 2016 Elsevier B.V. All rights reserved.
Die Oberflächentechnik ist eine Schlüsseltechnologie in nahezu zu allen industriellen Branchen. Mit Ausnahme der mechanischen Stabilität, die das Substrat bereitstellt, werden verschiedenartigste Funktionen materialsparend, zum Teil hochintegriert mit maßgeschneiderten Schichtdesigns unter Ausnutzung von Nano- und Quanteneffekten auf Oberflächen appliziert. Ein Großteil der Fertigungskosten in der Mikro- und Nanotechnik wird durch Reinräume und die Umsetzung ausgeklügelter Reinigungsstrategien zur Vermeidung von Restverschmutzungen und partikulären Belegungen
verursacht, da diese unweigerlich zum Bauteilversagen führen. Die Validierung des Reinigungszustandes ist somit von zentraler Bedeutung für die Schichtqualität und Produktfunktionalität. Dies gilt in Abhängigkeit von der Applikation und den vertikalen Schicht- bzw. lateralen Strukturdimensionen sowohl für Fertigungsprozesse im Reinraum als auch für solche in robuster Umgebung. In der Praxis kommt es häufig vor, dass man mikroskopisch scheinbar saubere Substrate erst durch die Beschichtung „enttarnt" und dann Defekte oft mit bloßem Auge sichtbar werden. Noch problematischer ist der Einbau von Verunreinigungen während der Schichtabscheidung, die zunächst nicht sichtbar sind, dann aber zum Bauteilversagen führen.
Vibrational cooling in the liquid phase studied by ultrafast investigations of cycloheptatriene
(2009)
Solvent-mediated vibrational relaxation in UV pump-probe experiments has been studied using cycloheptatriene (CHT) and its perdeuterated counterpart (CHTd8) as model systems. Transient spectra containing absolute e(t) values are obtained by a modified Sulzer-Wieland ansatz and a global fit function for vibrational relaxation is proposed.
Ellipsometry is a useful tool for studying the optical properties of thin films such as photovoltaic devices. We employ Müller matrix ellipsometry to study the thin film photovoltaic material copper indium gallium selenide Cu(In,Ga) Se2 (CIGS), a commercially relevant material with high energy conversion efficiency. Confocal microscopy reveals an rms roughness of 68 nm, which greatly affects the ellipsometry data. Rayleigh-Rice theory is employed to account for the optical properties of the surface roughness in the ellipsometry experiment, and a library search method is used to compare Müller parameters calculated for various CIGS compositions, to the measured data. The Müller parameters calculated with the Rayleigh-Rice model are found to correspond well with the measured data, and a surface roughness of 37nm and a correlation length of 125nm are extracted.
Using ultrafast X-ray diffraction, we study the coherent picosecond lattice dynamics of photoexcited thin films in the two limiting cases, where the photoinduced stress profile decays on a length scale larger and smaller than the film thickness. We solve a unifying analytical model of the strain propagation for acoustic impedance-matched opaque films on a semi-infinite transparent substrate, showing that the lattice dynamics essentially depend on two parameters: One for the spatial profile and one for the amplitude of the strain. We illustrate the results by comparison with high-quality ultrafast X-ray diffraction data of SrRuO3 films on SrTiO3 substrates.
In this paper, safety-related experiments with ultra-short laser pulses (down to 30 fs) on various components
(goggles, curtains) for laser protection are presented. The damage and failure behaviour of
protective devices has been investigated dependent on practical conditions such as pulse duration, laser
.uence, pulse number, and repetition rate.
The e.ects of laser-irradiation on materials can be roughly divided into transient ones like laserinduced
transmission (LIT) or short-lived colour centres and permanent damages like the stable colour
centres and ablation. The former e.ects are particularly important for transparent devices like laser
goggles.
To obtain a complete overview on laser safety issues and the prevention of failure there are two
important .elds of investigation:
1. the e.ects of laser radiation on human eyes and skin, and
2. on the possible protection materials.
Both .elds have been addressed during the recently .nished German project SAFEST (safety aspects
in femtosecond technology). The amount of safety data available in the ultrashort pulse region has
been increased remarkably. This allows for a re-evaluation of known laser protection materials for this
region of pulse durations and for the evaluation of new designs that promise high protection levels
while being light-weight and convenient to use.
Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.
Dielectric, anti-reflective or high reflective systems consist of low and high refractive index layers. Common systems are oxides. The preparation of low refractive index MgF2-films of optical quality by means of an anhydrous low temperature solgel synthesis is presented. The MgF2-sol is prepared by spin-coating on silicon and glass substrates. Various film thicknesses between 20 nm and 435 nm have been deposited. It has been shown that the thickness increase is proportional to the number of coating steps. The deposited MgF2-films consist of 10 nm to 20 nm large nanoparticles and have smooth surfaces with an average roughness (Ra) of (1.7 ± 0.3) nm. The optical constants n and k of the films are in agreement with the literature data of bulk-MgF2.