G.R. Sagatelian1, A.V. Shishlov2, M.N. Bilinkin3

1 Bauman Moscow State Technical University (Moscow, Russia)

2,3 Division of JSC TsENKI – "Kuznetsov research institute of applied mechanics"

The wave solid-state gyroscope (WSG) is a new generation device capable of responding to changes in the orientation of the body on which it is mounted relating to the inertial reference frame. Such gyroscopes do not have a rotating rotor, instead of which a part of a complex shape called a resonator is used. Resonators, which are a thin-walled shell in the form of a hemisphere made of silica, have the best performance characteristics.

To sustain resonant vibrations of the shell and provide communication with the electronic control system, a thin-film metal coating is applied to the inner surface of the hemisphere. Its presence leads to a decrease in the Q-factor of the resonator as a whole, and the uneven distribution of its thickness leads to distortions of information signals from the resonator. Minimizing the dissipation of oscillation energy in a thin-film coating is achieved by using magnetron sputtering, which ensures minimization of internal friction in the metal of coating.

The growth rate of the coating thickness at each point of the sprayed surface depends on the distance from this point to the emission point of the sprayed material, as well as on the emission and condensation angles. Since the sprayed surface has a spherical shape, and the sprayed material is emitted from an annular zone formed on the target by a magnetron, it is obvious that it is impossible to ensure an ideal uniformity of the coating thickness distribution over the entire sprayed surface.

The problem of minimizing the unevenness of thickness of the coating is solved by optimizing the kinematic and geometric parameters of the process, in which the resonator, mounted obliquely, performs two rotational movements – around its own axis and around the axis of the carousel. The inclined arrangement is necessary to ensure the deposition of metal on the leg of resonator, provided in its design as a support that reduces the dissipation of oscillation energy. 

The analytical optimization had taken into account the fact that zones appear on the sprayed surface, shaded by the leg of resonator and the contour of a thin-walled hemispherical shell. The optimal configuration of the aperture in the screen located between the magnetron and the sprayed part in the immediate vicinity of the target was established. The configuration of aperture ensures the formation of a metal coating of increased thickness on the leg while minimizing deviations from the thickness of the coating on the surface of the hemisphere.

To clarify the analytically obtained result, experimental studies were carried out with the replacement of a spherical surface with a set of adjacent flat surfaces of witness specimens located along the meridian of the inner hemisphere. The thickness of the coating on the flat witness samples was determined by profilography. The obtained distribution of the coating thickness along the meridian of the hemisphere made it possible to adjust the configuration of the corresponding section of the aperture in the screen.

As a practical implementation, a screen has been developed containing three special holes corresponding to spraying on the end of the leg, on the cylindrical surface of the leg and on the inner hemisphere. To eliminate the negative consequences of oblique spraying, an additional flap with a narrow slit is used, located in close proximity to the edge of the hemispherical shell.

Sagatelian G.R., Shishlov A.V., Bilinkin M.N. Features of magnetron sputtering of internal spherical surfaces. Nanotechnology: development and applications – XXI century. 2021 V. 13. № 4. P. 46–59. DOI: https://doi.org/10.18127/j22250980-202104-05 (in Russian)

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