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Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy
Frolec, Jiří ; Králík, Tomáš ; Musilová, Věra ; Urban, Pavel
The article provides experimental analysis of total hemispherical emissivity and absorptivity of Ti-6Al-4V alloy before and after deposition of 1-2 .pí.m gold layer. We measured their dependences on the temperature of thermal radiation (varying from 20 K to 320 K) and confronted these results with mechanically polished copper, i.e. with material known for extremely low emissivity and absorptivity. Galvanic deposition of pure gold resulted in significant lowering of original emissivity of Ti-6Al-4V bare surfaces from 15.8 percent to 3.4 percent at 300 K and from 4.1 percent to 1.1 percent at 20 K. Our findings about thermal-radiative properties have practical relevance for an improvement of a low temperature part of an ultra-high vacuum scanning probe microscope\n(UHV-SPM) designed by our group and could also be useful for other applications and low temperature systems.
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Blaze Gratings with a Ribbed Back Slope
Krátký, Stanislav ; Meluzín, Petr ; Horáček, Miroslav ; Kolařík, Vladimír ; Matějka, Milan ; Chlumská, Jana ; Král, Stanislav
Binary relief phase-modulated gratings provide symmetrical diffraction of the incoming light beam. Asymmetrical gratings, e.g. asymmetrical triangular blazed gratings, are characteristic by an asymmetrical diffraction behavior, where one of the first diffraction orders is more important than the other one. Electron beam lithography is a suitable and flexible tool for patterning of such kind of gratings. High quality results can be readily obtained when the period of the grating is relatively large and the relief depth is relatively low, this is the case of gratings with a small blaze angle. As the blaze angle increases, the quality of result suffers from several patterning-related issues. One of the problems is a reflection of the incoming light beam from the back slope (anti-blaze facet) of the blaze grating. We propose a novel configuration, with a ribbed modulation of the back slope. This modulation is perpendicular to the direction of the grating grooves. This paper presents an analysis of the proposed blazed grating configuration. E-beam pattern generators were used to prepare a few\nsamples of blaze gratings with a ribbed back slope. One part of the experiment was performed with a Gaussianshaped beam and another one with the variable-shaped beam. Results of the experiment are presented.\nFinally, we discuss the optical performance of two blaze gratings with similar parameters, one of them is with the flat back slope and another one is with the ribbed back slope.
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Parameter Optimization of Multi-Level Diffraction Gratings
Matějka, Milan ; Kolařík, Vladimír ; Horáček, Miroslav ; Král, Stanislav
Originally, the e-beam lithography (EBL) is a technique for creating high-resolution black and white masks for the optical lithography. Multi-level relief structures can be also prepared using EBL patterning. Their preparation is based on the image patterning with a gradient of exposure doses. Large-area multi-level structures can be effectively prepared using the electron beam pattern generator with a variable shaped beam. We present several writing strategies. Basically, the main writing strategy uses one stamp (i.e. one elementary exposure of the shaped electron beam) per one elementary area with the same exposure dose. This simple approach is fast and flexible, however it does not guarantee optimal results. The main problem is an imperfection of the stamps (size, shape, and homogeneity). Advanced algorithms are based on multiple\nexposure of the same elementary area, the total local exposure dose is a sum of several different elementary exposures (stamps). Using these algorithms, a smoother surface of the structure can be achieved. On the other hand, the writing speed is considerably decreased. Tradeoff between the achieved parameters and the writing speed is discussed for selected set of writing strategy algorithms.
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Nanopatterning of Silicon Nitride Membranes
Matějka, Milan ; Krátký, Stanislav ; Řiháček, Tomáš ; Kolařík, Vladimír ; Chlumská, Jana ; Urbánek, Michal
Membranes are typically created by a thin silicon nitride (SIN) layer deposited on a silicon wafer. Both, top and bottom side of the wafer is covered by a thin layer of the silicon nitride. The principle of silicon nitride membranes preparation is based on the wet anisotropic etching of the bottom side of the silicon wafer with crystallographic orientation (100). While the basic procedure for the preparation of such membranes is well known, the nano patterning of thin membranes presents quite important challenges. This is partially due to the mechanical stress which is typically presented within such membranes. The resolution requirements of the membrane patterning have gradually increased. Advanced lithographic techniques and etching procedures had to be developed. This paper summarizes theoretical aspects, technological issues and achieved results. The application potential of silicon nitride membranes as a base for multifunctional micro system (MMS) is also\ndiscussed.
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Structural Colors of Self-Similar Nano Patterns
Meluzín, Petr ; Horáček, Miroslav ; Krátký, Stanislav ; Kolařík, Vladimír
E-beam lithography is a flexible technology for various diffraction gratings origination. The e-beam patterning typically allows for the creation of optical diffraction gratings in the first diffraction order. However, the very high resolution enables also the patterning of structures providing the zero-order diffraction. Recently, we presented a work on the structural colors of metallic layers covering both regular-line structures and CGH (computer generated hologram) structures. This work presents a study dealing with zero-order diffraction structures with self-similar properties. The practical part of the work is focused on two aspects: design parameters and technological issues. Variations in design parameters include the tone of the structure (positive or negative),\nthe density of filling, the filling factor, and the depth of the structures. The achieved gamut of colors may by primarily extended by the proper selection of metal deposition technology and its parameters, and further by the proper selection of the metal and the thickness of its layer, these are the technological issues.
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Phyllotactic Model Linking Nano and Macro World
Horáček, Miroslav ; Meluzín, Petr ; Krátký, Stanislav ; Urbánek, Michal ; Bok, Jan ; Kolařík, Vladimír
Recently, the arrangement of diffraction primitives according to a phyllotactic model was presented. This arrangement was used to benchmarking purposes of the e-beam writer nano patterning. The phyllotactic arrangement has several interesting properties. One of them is related with the coherence between the nanoor microscopic domain of individual optical primitives and the properties of visually perceived images crated by these structures in the macro domain. This paper presents theoretical analysis of the phyllotactic arrangement in the referred context. Different approaches enabling the creation of diffractive optically variable images are proposed. The practical part of the presented work deals with the nano patterning of such structures using two different types of the e-beam pattern generators. One of them is a system with a variable shaped beam of electrons, while the other one is a system with a Gaussian-shaped beam. E-beam writing strategies and the use of inherent spiral patterns for exposure ordering and partitioning are also discussed.
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Laser and Phyllotaxy
Kolařík, Vladimír ; Horáček, Miroslav ; Krátký, Stanislav ; Meluzín, Petr ; Chlumská, Jana ; Matějka, Milan ; Král, Stanislav
The paper presents planar diffractive structures with optical elements arranged in positions according to a phyllotactic model. Further, we discuss the creation of a diffractive phyllotactic pattern and its properties. One of the particular arrangements, a nesting of two different phyllotactic models possessing a different level of fineness, is described in details. The discussed arrangement of elements within a circle can be used also in the laser beam splitting application.
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Large-area gray-scale structures in e-beam writer versus area current homogeneity and deflection uniformity
Kolařík, Vladimír ; Horáček, Miroslav ; Matějka, Milan ; Krátký, Stanislav ; Bok, Jan
The high stability and good current homogeneity in the spot of the e-beam writer is crucial to the exposure quality, particularly in the case of large-area structures when gray-scale lithography is used. Even though the deflection field distortion is calibrated regularly and beam focus and beam astigmatism is dynamically corrected over the entire deflection field,\nwe can observe disturbances in the exposed relief for both nowadays types of e-beam writers, the shaped e-beam writing system and the Gaussian e-beam writing system. A stable and homogeneous angular current density distribution in the spot is important especially in the case of shaped e-beam lithography systems. A non-homogeneity of the spot over deflection field is seen alongside the field boundaries of both lithography systems.
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Measurement of real-time gigacycle fatigue through real-time interferometry
Lazar, Josef ; Holá, Miroslava ; Hrabina, Jan ; Číp, Ondřej
We present an interferometric method for measurement of strain induced deformation of metal samples in experiments inducing high-cycle fatigue. The motivation is to get real-time information about the deformation of a metal sample under test, its elongation imposed by fast vibrating actuator. Fatigue of materials is a process of degradation of a material due to repeated application of forces which includes nucleation and propagation of cracks and leads to the failure of the component. It may appear in all parts of machines or structures which rotate, vibrate, are repeatedly loaded, are subjected to temperature gradients etc., so statistically, fatigue is implied in about 80% of all industrial failures.
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