**1. Introduction**

132 Advanced Photonic Sciences

[24] R.W. Hopper, Stochastic theory of scattering from idealized spinodal structures: ІІ.

V.70, №1, Р.111-117.

Scattering in general and for the basic late stage model, J. Non-Cryst. Solids, 1985,

The further progress in photonics, as well as in many other technological fields is connected with application of new materials. Fianite is the material of such kind. Fianites are single crystals of zirconia- or hafnia-based cubic solid solutions with yttrium, calcium, magnesium or lanthanides (from gadolinium to lutetium) stabilizing oxides (ZrO2 (HfO2)·R2O3, where R - Y, Gd … Lu). Industrial technology of synthesis of fianite has been for the first time developed in Russia in the Lebedev Physical Institute of the Russian Academy of Sciences (FIAN in Russian), as has entitled crystals[1, 2]. Serial production of the crystals has been already started in the early seventies of XX century [3-5]. Currently, fianite crystals are in the second position by the volume of worldwide production following silicon. Fianite single crystals – zirconia-based solid solutions (or "yttrium stabilized zirconia" - YSZ) are widely known worldwide as jewelry material (fig. 1).

Fig. 1. Great color variety of the crystals combined with unique optical properties makes fianite single crystals a promising material for jewellery, arts and Crafts (left); fianite substrates 3" in diameter (right).

Recently, in the countries with the developed microelectronics a significant growth of interest to various aspects of fianite application in semiconductor technologies has been observed. Fianite is an extremely promising multipurpose material for new optoelectronics technologies due to its unique combination of physical and chemical properties. It can be used in virtually all of the main technological stages of the production of micro-, opto- and SHF-electronics: as a bulk dielectric substrate, a material for buffer layers in heteroepitaxy; a material for insulating, antireflection, and protective layers in the devices and as a gate dielectric [6-22].

Fianite in Photonics 135

Fianite lend itself to a machining considerably readily, similarly to sapphire crystals.

*Pre-epitaxial treatment of surface of the substrates.* With the purpose to guarantee optimal physical-chemical state of fianite substrates various techniques and conditions of preepitaxial treatment have been studied. Treatment at 1000-1400С temperatures in air during 1-4 h was used as one of such techniques. The high-temperature annealing provides a relief of stress occurred in the surface layer at mechanical treatment, removal of impurities from

The effect of high-temperature annealing on surface quality of the substrates has been studied. In Fig.3a scratches occurred in course of polishing of the substrate by ACM 1/0 diamond paste are apparently observable. The following annealing (12500 С in air) did not result in smoothing of the relief as a whole but caused re-structuring of the surface layer (Fig. 3b) and flatten the relief in micro-locations at scratch residues and results in 2-3-fold

Fig. 3. AFM image of fianite substrate (left) and surface profile (right) after chemical-

substrate surface. The HWRC values significantly decreased due to the annealing.

The studies of the effect of thermal treatment of the substrates on roughness of polished surface have shown that high-temperature annealing (1250-14000 С) conducted following chemo-mechanical treatment promoted an increase of structural and phase homogeneity of

Half-width of the rocking curve (HWRC) is another parameter featuring quality of a

mechanical polishing (a) and subsequent high temperature annealing (b).

the surface of zirconia-based crystal substrates.

Followed by annealing (21000С, vacuum) dislocation density decreased to 102 -103сm-2.

Dislocation densities in ZrO2 – (8-20) mol% Y2O3 crystals have been measured:

**2.2 Technology for mechanical machining of fianite crystals** 

the surface and increasing of phase and structural perfection.

decrease of high bump- valley drops (Fig. 3, right side)

in central parts – 103 сm-2 in periphery – 105сm-2

The use of fianite, as well as ZrO2 and НfO2 oxides instead of SiO2 as gate dielectrics in CMOC technology, which can be considered for microelectronics as a basic one, is of peculiar interest [14, 15]. That is associated with the increase of leakage currents by the increase of the integration level when conventional SiO2 is used. Therefore, a change of SiO2 over dielectrics with higher values of dielectric constant (high-k-materials) is required. Due to higher value of dielectric constant (25÷30 for fianite [4, 14, 15] instead of 12 for SiO2) it is possible to provide the same electric capacity using much more thick layers of the gate oxide.

A number of modern aspects of the application of fianite in photonics are analyzed in this chapter.
