Stanislav Kraev

This study proposes a method for detecting small-length fluctuations for fiber-optic sensors (FOS). The method is based on a tracking tandem low-coherence interferometer and enables the ability to compensate for temperature and deformation drifts in FOS. As a result, the constant high sensitivity of FOS over a wide frequency range is guaranteed. Sensitivity to the level of 2 nm in the frequency range of 200 kHz has been demonstrated. The operation of the circuit is demonstrated on the example of the 2D location of acoustic signals using a correlation algorithm for signal processing, known as the time reversal method. It is shown that this system enables us to determine the place of the impact on the sample under the test with an accuracy of about 2 cm using a single sensor.

The paper proposes a technology based on UV-LIGA process for microoptoelectromechanical systems (MOEMS) manufacturing. We used the original combination of materials and technological steps, in which any of the materials does not enter chemical reactions with each other, while all of them are weakly sensitive to the effects of oxygen plasma. This made it suitable for long-term etching in the oxygen plasma at low discharge power with the complete preservation of the original geometry, including small parts. The micromembranes were formed by thermal evaporation of Al. This simplified the technique compared to the classic UV-LIGA and guaranteed high quality and uniformity of the resulting structure. To demonstrate the complete process, a test MOEMS with electrostatic control was manufactured. On one chip, a set of micromembranes was created with different stiffness from 10 nm/V to 100 nm/V and various working ranges from 100 to 300 nm. All membranes have a flat frequency response without resonant peaks in the frequency range 0–200 kHz. The proposed technology potentially enables the manufacture of wide low-height membranes of complex geometry to create microoptic fiber sensors.

In this work, the dependence of plasma-chemical etching rate and the roughness of the surface of gallium arsenide crater on chloropentafluoroethane (C2F5Cl) concentration in a mixture with chlorine, forward power and etching duration were studied. Characteristics of GaAs etching crater were studied by white light interferometry and scanning electron microscopy. It is shown that C2F5Cl addition in chlorine-containing inductively coupled plasma led to a nonlinear change of gallium arsenide etching rate with time which can be explained by passivation of substrate surface at the initial stage by products of freon decay. Along with this, characteristics of the etching profile of GaAs are significantly improved. Forward power increase contributes to development of roughness, while the etching rate increases nonlinearly.

In this paper describes the process of manufacturing ohmic contacts to diamond-like carbon (DLC) layer by depositing of Au/Mo/Ti metal layers. Contacts had good mechanical and adhesive properties. Their contact resistivity ranged from 1.4 ∙ 10-4 to 6.4 ∙ 10-5 Ohm ∙ cm2 depending on the DLC layer thickness. The temperature dependence of the films sheet resistance was studied. It is shown that thin DLC layers provide better ohmic contact characteristics due to their more uniform graphitization during thermal annealing.