During the post-annealing and cooling process of CoSb 3 thin films deposited on thermally oxidized Si(100) substrates, cracks occur at the surface of the films, which can be caused by the difference in thermal expansion coefficient of the substrate and the film. To investigate the crack formation, 40-nm-thick CoSb 3 films were deposited at room temperature under ultrahigh vacuum (UHV) conditions onto various substrates, exhibiting different thermal expansion coefficients (2 Â 10 À6 to 12 Â 10 À6 K À1 ). All samples were post-annealed in UHV at 500 8C for 1 h. The composition of the films was verified by Rutherford backscattering spectrometry. The phase formation and elastic stress of the films were analyzed by X-ray diffraction, confirming the formation of the desired skutterudite phase, while the individual grains were studied by electron backscatter diffraction. In addition, the surface morphology and the roughness of the films were investigated by atomic force microscopy. For substrates with a thermal expansion coefficient between 9 Â 10 À6 and 11 Â 10 À6 K À1 , crack formation can be prevented and a minimum in roughness was found, resulting also in a minimal value of the electrical resistivity.
This paper analyzes wavelength drifts of a Fiber Bragg Grating interrogation device due to variations in different environmental conditions. First, the thermal induced wavelength shifts of the Fiber Bragg Gratings were abstracted. Then, it was possible to investigate the correlations between wavelength drifts and A) temperature of the interrogation device, B) air pressure, and C) static inclination of the interrogation device. Out of these three factors, unsteady temperature of the interrogation device proved to be the main reason for wavelength drift in our setup. Variations in air pressure were the second most important factor, whereas the static inclination of the interrogation device showed the least but still considerable effect on wavelength drifts. A temperature stabilization of the device housing temperature is introduced and a software-based offsetting of the air pressure is discussed.
This paper introduces a pressure sensor catheter with two different measurement principles. A Fabry-Perot- Interferometer at the fiber tip is formed by a reflective multilayer membrane of a pressure sensor chip. The cavity provides absolute pressure sensing. 20 millimeter before the fiber tip a Fiber Bragg Grating is integrated for additional temperature sensing. The sensing components are completely coated with a silicone mantle of 2 mm diameter. The signal evaluation is both done with a Fiber Bragg Grating interrogation device. First, mechanical structure aspects of the manufactured fiber-optic hybrid sensor as well as the sensing principle is described. Then, experimental results, including quantification and separation of pressure and temperature sensitivity are presented. Out of these characteristics the possibility for absolute pressure sensing with temperature compensation for the application as a pressure sensor catheter is confirmed.
This paper introduces an absolute pressure sensor based on an extrinsic fiber-optic Fabry-Pérot-Interferometer molded into a silicone catheter. The interferometer principle is formed between the tip of an optical fiber and a reflective multilayer membrane containing aluminum nitride. The signal analysis is done by a Fiber Bragg Grating interrogation device. First, the optical sensing principle as pressure sensor in an invasive catheter with a diameter of 1 mm is described. Then, the dependence of the optical signal on changes of hydrostatic pressure and ambient temperature is shown. Out of these characteristics it was possible to evaluate the pressure sensor catheter for potential application in the human vascular system.
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