RU2477711C1 - Doped quartz glass with tetrahedral coordination of titanium atoms - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to doped quartz glass with a tetrahedral coordination of titanium atoms and can be used in designing optoelectronic and light-emitting devices. The doped quartz glass with tetrahedral coordination of titanium atoms is a base which consists of silicon dioxide with a surface layer containing titanium dioxide and silicon dioxide. The surface layer has thickness of 35-45 nm, contains 7-12 mol % titanium dioxide and 93-88 mol % silicon dioxide, wherein 97-99% of titanium atoms are in tetrahedral coordination.

EFFECT: improved optical transparency and wider field of use.

1 tbl, 1 dwg

Description

The invention relates to doped quartz glasses with tetrahedral coordination of titanium atoms and can be used to create components of micro- (nano-) and optoelectronic devices.

It is known [R.Ya. Khodakovskaya. Chemistry of titanium-containing glasses and glass. Chemistry, 1978, p.5] that the presence of titanium ions in the amorphous structure of silica glass (SiO ₂ ) has a significant effect on its physical properties, for example, the elastic modulus, thermal expansion coefficient, photo and cathodoluminescence, optical absorption, transmission and refraction, electrical resistance. Therefore, titanium-doped quartz glasses (obtained by chemical synthesis) are used in optics, the chemical industry, high-temperature technology, and electronics. In micro- and optoelectronics, quartz glass is used with high requirements for stability characteristics. It is also known [R.Ya. Khodakovskaya. Chemistry of titanium-containing glasses and glass. p. 14], that in the vast majority of crystalline oxygen compounds, titanium has an octahedral coordination. The tetrahedral coordination of titanium impurity ions Ti ^{4+ was} found, for example, in the oxygen compound of titanium with barium Ba ₂ TiO ₄ [Bland E. Acta Cristallograph., 1961, v.14, p.875-881].

Known silicon-containing material in the form of a fresnoite mineral with tetrahedral coordination of titanium atoms [A.M. Coats, N. Hirose, J. Maar, ARWest. Tetrahedral Ti ⁴⁺ in the Solid Solution Ba ₂ Ti _{1 + x} Si _2-x O ₈ (0≤x≤0.14) J. Solid-State Chem. 126, 105 (1996)], obtained by mechanical and heat treatment of pre-dried BaCO ₃ , TiO ₂ and SiO ₂ reagents taken in stoichiometric amounts. In the obtained material of the general formula Ba ₂ Ti _{1 + x} Si _2-x O ₈ (0≤x≤0.14) with tetrahedral coordination of titanium atoms, tetravalent titanium atoms (Ti ⁴⁺ ions) partially replace silicon atoms in the crystal structure, forming titanium-oxygen tetrahedra.

The disadvantage of the material is the complicated chemical composition and low percentage of titanium impurity atoms (Ti ⁴⁺ ions) with tetrahedral coordination, which does not provide the required properties when creating functional devices of microelectronics, optoelectronics, nanophotonics on the basis of this material, the field of use of the material is limited.

Closest to the proposed is doped silica glass with tetrahedral coordination of titanium atoms, which is a base consisting of silicon dioxide, with a surface layer comprising titanium dioxide and silicon dioxide [V. Belostotsky, Journal of Non-Crystalline Solids Volume 202, Issues 1- 2, 1 July 1996, Pages 194-197]. This glass was obtained by implanting titanium ions Ti ⁺ with an energy of 50 keV in a continuous mode of irradiation, with an irradiation dose of 2 × 10 ¹⁷ cm ^-2 , at a temperature of silica glass of 670 K during implantation, followed by annealing at a temperature of 1070 ÷ 1100 K.

Along with titanium atoms in tetrahedral coordination, the prototype glass includes titanium ions Ti ²⁺ and Ti ³⁺ that are not in tetrahedral coordination. In this case, optical transparency (light transmission) is deteriorated in the visible spectrum and near ultraviolet range. The area of practical use of glass is limited.

The objective of the invention is to improve the optical transparency of doped silica glass with tetrahedral coordination of titanium atoms, expanding the scope of its use. To solve this problem, doped quartz glass with tetrahedral coordination of titanium atoms is proposed, which is a base consisting of silicon dioxide with a surface layer comprising titanium dioxide and silicon dioxide, characterized in that the thickness of the surface layer is 35-45 nm, the surface layer contains 7-12 mol. % titanium dioxide and 93-88 mol.% silicon dioxide, while in the tetrahedral coordination is 97 ÷ 99% of titanium atoms.

A new technical result of the proposed alloyed quartz glass with tetrahedral coordination of titanium atoms is to improve optical transparency and expand the scope of use. The result is ensured by the fact that the thickness of the surface layer of the glass is 35-45 nm, the surface layer contains 7-12 mol. % titanium dioxide TiO ₂ and 93-88 mol.% silicon dioxide SiO ₂ , while in the tetrahedral coordination is 97 ÷ 99% of titanium atoms (Ti ⁴⁺ ). The proposed doped quartz glass, which has significant advantages in comparison with known similar materials, the authors assigned the name "Tisil".

The drawing shows x-ray absorption spectra of the proposed doped quartz glass. The vertical axis represents the normalized absorption in arbitrary units (conventional units), and the horizontal axis represents the energy of x-ray photons (eV). The indicated spectra are shown for two samples of silica glass SiO ₂ implanted with titanium ions with doses of 5 × 10 ¹⁶ and 1 × 10 ¹⁵ cm ^-2 . In addition, the corresponding spectrum of synthetic fresnoite Ba ₂ TiSi ₂ O ₈ containing titanium atoms with tetrahedral coordination [T. Höche, H.-I. Kleebe, R. Brydson. Phylosoph. Magazine, A 81, 825 (2001)]. The letters A, B, C, D, D and vertical dashed lines indicate the spectral bands, within which a comparison of the nature of the curves indicates the presence or absence of titanium atoms with tetrahedral coordination in the obtained samples of doped silica glass. The coincidence in all the indicated bands of the curve shapes for fresnoite and for a quartz glass sample implanted with titanium ions with a dose of 5 × 10 ¹⁶ cm ^-2 allows us to conclude that there are titanium atoms with tetrahedral coordination in this sample. The mismatch in bands B and D of the shapes of the curves for fresnoite and for a quartz glass sample implanted with titanium ions with a dose of 1 × 10 ¹⁵ cm ^-2 indicates the absence of titanium atoms with tetrahedral coordination in this sample.

The table shows the irradiation modes of titanium ions and the parameters of samples (1, 2, 3) of the proposed doped quartz glass with tetrahedral coordination of Ti ⁴⁺ titanium atoms obtained by implantation of titanium ions in a pulsed mode.

Sample No. Dose and current density (cm ^-2 ; mA / cm ² ) Titanium ion energy (keV) Layer thickness (nm) TiO ₂ / SiO ₂ (mol%) Ti ⁴⁺ (%) one 5 × 10 ¹⁶ ; 5 thirty 39 9/91 98 2 9 × 10 ¹⁶ ; 10 35 45 12/88 99 5 1 × 10 ¹⁶ ; 0.2 25 35 7/93 97

The implantation of titanium ions Ti ⁺ into silica glass SiO _{2 was} carried out using an ion source operating in a pulsed mode (pulse duration 400 μs, repetition frequency 25 Hz), at the above values of the radiation dose, pulsed current density and ion energy. The temperature of quartz glass was kept constant in the range of 250–300 ° C.

The obtained samples of doped quartz glass are plane-parallel plates with an area of 1 cm ² , a thickness of 3 mm with a surface of optical quality. The surface layer of each sample indicated in the table thickness contains titanium dioxide and silicon dioxide, the underlying sample base consists of silicon dioxide. The characteristic size of the structural unit of silica glass impulse implanted with titanium ions, namely, a titanium-oxygen tetrahedron, is 10–12 Å (approximately 1 nm). The x-ray absorption spectrum of the proposed quartz glass shown in the drawing (radiation dose of 5 × 10 ¹⁶ cm ^-2 ) fully corresponds to the absorption spectrum of fresnoite shown in the same drawing, which also includes titanium atoms with tetrahedral coordination.

Doped quartz glass with tetrahedral coordination of titanium atoms according to the prototype [V. Belototsky, Journal of Non-Crystalline Solids Volume 202, Issues 1-2, 1 July 1996, Pages 194-197] contains optical absorption bands of 1.77 eV, 2.8 eV and 3.95 eV, due to the presence of titanium ions Ti ²⁺ and Ti ³⁺ in this glass, which are not in tetrahedral coordination, which impairs the optical transparency of the glass. The obtained samples of doped silica glass with tetrahedral coordination of titanium atoms do not contain the mentioned titanium ions, as a result of which the proposed glass has improved optical transparency. This makes it possible to use the proposed glass for the manufacture of planar waveguides for the wavelength interval 300 ÷ 800 nm.

Claims (1)

Doped silica glass with tetrahedral coordination of titanium atoms, which is a base consisting of silicon dioxide, with a surface layer comprising titanium dioxide and silicon dioxide, characterized in that the thickness of the surface layer is 35-45 nm, the surface layer contains 7-12 mol. % titanium dioxide and 93-88 mol.% silicon dioxide, while in the tetrahedral coordination is 97 ÷ 99% of titanium atoms.

Images