DD151771A1 - TWO-LAYER BODY AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The invention relates to a two-layer body of a single-crystal magnesium oxide substrate and a well-grown, monocrystalline layer of magnesium ortho-titanate or a solid solution, one component of which is magnesium ortho-titanate, and a method for producing this Zweischichtkoerpers, which is a combination of a known or other methods for depositing a layer of TiO & ind2! (or other oxides) with a topotaktischen Festkoerperreaktion proceeding simultaneously with the deposition. The object of the invention is to provide a two-layer body which can be used in the art and which is suitable as a model object for basic investigations in solid state physics, as well as to provide an effective method for producing the high-quality two-layer body according to the invention. This method can also be used for the production of other two-layer bodies, if their layer component can be represented by a topotactic solid-state reaction of which one starting material is the substrate component of the two-layer body.

Description

Two-layer body and process of its manufacture.

Field of application of the invention

The invention relates to a two-layer body (ZSK), consisting of a single-crystalline MgO substrate and a monocrystalline layer of high crystalline perfection, and a process for its preparation, wherein the layer of Mg ₂ TiO. or consists of a solid solution, one component of which is Mg2TiO. is.

This ZSK is of interest for the investigation of basic relationships of epi- and topotaxy in science and can be used to advantage in various fields of technology thanks to its dielectric, optical, thermal and mechanical properties. Similar bilayer bodies, but of a different chemical and crystallographic nature, and consequently with z.T. other properties are successfully used in integrated solid state electronics, magnetic memory technology, and optoelectronics, or their use is imminent. The preparation process according to the invention can also be used for the preparation of other ZSK whose layer component can be prepared by means of a topotactic solid-state reaction with the substrate.

Characteristic of the known technical solutions

Two-layer body consisting of a monocrystalline substrate and an oriented grown monocrystalline layer

order, have been known for some time and are successfully applied in the art or prepared for use. Known ZSK are, for example, GaAs / GaAlAs; Bi ₄ Ti ₃ O ₁₂ / MgO; LiflbO ₃ / LiTaO ₃ .

Each of the known ZSK has certain advantages that make it suitable for certain technical applications, as well as certain adverse properties that exclude other technical applications. These properties are determined, on the one hand, by the physical and chemical properties of the particular chemical compound used, and, on the other hand, by a variety of quality which, in turn, are mainly determined by the nature and management of the manufacturing process. In particular, these quality features relate to stoichiometry, crystalline perfection (high degree of Binkrista linearity, low density of crystal defects), the quality of the layer surface, and the adhesion of the layer to the substrate. The chemical and crystallographic nature of the ZSK, its quality characteristics and the method used to produce it must therefore be assessed together when assessing the technical applicability.

None of the known ZSK and none of the known manufacturing methods can be said to be universally applicable. "The outrageous, often unique properties of a particular ZSK are suitable for a particular application or for a few types of applications. As a result of this relatively narrow scope of each ZSK a wide range of different ZSK is required, among other things as many different requirements on the part of the technology to meet. The existing spectrum of the ZSK in this sense can not be called wide enough. ZSK, the good Isoiat ore igenschäften and certain optical properties with very high thermal stability and hoter mechanical hardness

and that can be prepared by such processes which highly preclude contamination of the layer material and the sintering layer. Since even at temperatures well below the angle of incidence, diffusion and reaction processes can utilize the useful layer properties of the ZSK and since these temperatures are generally higher the higher the melting point, materials with a very high melting point are advantageous in this regard. However, they should, i.a. for reasons of longevity, be mechanically as stable as possible. Both requirements are rarely met by materials selected for other technical applications for other reasons.

By way of example, it should be noted that a number of materials that are incorporated into ZSK as a layer component that have been developed for integrated optics (InAs, InP, GaAs, LiFbO) have melting temperatures between S40 ° C and 1250 G but, on the other hand, have certain high melting point layer materials to be also used in the inte grie th optics (5-4 Mohs 3 ') possess (ZnS, Mp. 1700 ⁰ C, ZnO ₁ Mp. 1975 ° C) only low hardness.

With regard to the production process for the ZSK according to the invention, it is estimated that all known processes for the preparation of ZSK have disadvantages which rule out their use for producing the ZSK according to the invention or may not appear appropriate. The known methods have been considered: (a) vacuum evaporation, (b) ion plating, (c) electrolytic deposition, (d) liquid phase epitaxy, (e) multi-source vacuum evaporation, (f) flash vacuum evaporation, (g) sputtering, ( h) Chemical vapor deposition, (i) Chemical transport reaction, (3) Reactive vacuum evaporation, (k) Reactive cathode sputtering, (1) Thermal oxidation of single crystal metallic alloy layers,

(m) recrystallization of amorphous pillows, (η) deposition of a monocrystalline metal film and subsequent thermal oxidation under reaction with the oxide substrate.

The mentioned disadvantages are:

1. Formation of unstoichiometric layers due to the incongruent evaporation of Mg ^ TiO, (methods a and b).

2. Formation of layers with high defect density due to the fact that the film formation away from

Phase equilibrium takes place (method a, b, e, f, g and z.T. j, к and 1).

3. incorporation of impurities (methods d, h and i),

4 · Basic unsuitability due to the isolator properties of the ZSK (method c).

5. Unsuitability according to the current state of the art for suitable foaming reactors (methods h and i).

6. Short life of the apparatus used for the production due to reaction attack by oxygen (method j, к, 1 and η).

7. Ineffective manufacturing process due to several process steps (method 1, m and n) ·

REFERENCES

1. Handbook of Thin PiIm Technology. Editor: CI. Corn egg and R. glang. McGraw-Hill, New York, etc. 1970. Ch. 1,4,5,10.

2. Epitaxial Growth, eds .: J.V /. Matthews, Acad.Press, New York etc. 1975, chap. 2

3. Pe st body before mie. Ed .: V.Boldyrev and K. Meyer, VEB German publishing house for primary industry, Leipzig 1973, chap. 20.21.

Object of the invention

The object of the invention is to provide a ZSK which has none of the properties required for certain technical applications (in particular good dielectric and optical properties with high thermal and mechanical stability) and which in this combination are not yet exhibited by any of the known ZSK · The range of ZSK available for beneficial technical applications is thus extended. Advantages of the ZSK according to the invention are further its suitability for investigating the phenomena of epitope- and topotaxy and interfacial adaptation in the field of plague physics and the fact that it has properties that allow it to be produced simply, effectively and with high quality. The aim of the invention is also to provide a method that allows the ZSK according to the invention, as well as certain other ZSK to produce such that the layer component of the ZSK stoichiometric, pollution and baubarmearm, single crystal, with a smooth surface and smooth interface, and with defined, uniform thickness grows. Another advantage of the process according to the invention is that it proceeds at temperatures which are low in comparison to the melting temperatures of the compounds involved (MgOjTiO ₂ , Mg ₂ TiO ₃ , etc.).

Explanation of the essence of the invention

The two-layer body (ZSK) according to the invention consists of a monocrystalline MgO substrate, which may be a monocrystal or a monocrystalline thin layer, of arbitrary thickness, on which a monocrystalline layer in the below-mentioned V / iron is deposited, which consists of magnesium ortho. Titanate (Mg ₂ TiQ,) consists of or from a solid solution, whose εіде component Mg ₂ TiO. is and their others

Koaiponente is a magnesium-containing oxidic compound, which satisfies the properties of Mg ₂ TiO required by the respective scientific or technical application of the ZSK. changes only slightly or to a desired degree and which may at the same time offer the possibility of a specific variation of the lattice parameter of the layer (hereinafter referred to as "MgpTiO.-layer"). This other component may be, for example, one of the following compounds: MgAlgO., MgFe ₂ O ,, MgCr ₂ O ₄ , MgO. The Mg ₂ TiO.-layer can also be doped with ionic ions in order to achieve specific properties.

The Mg ₂ TiO ₂ layer is applied to a crystallographically defined, low indexed, flat, clean surface of the MgO substrate, in such a way that the following applies for the Miller indices of the adhesion plane and the lattice directions lying in it:

The interface between the substrate and the Mg ₂ Ti0 ₄ layer and the layer surface are flat, the MgpTiC ^ layer has a very low density of build defects (dislocations, planar defects) for layers of this type and is free of grains, domains, Channels and holes. The thickness of the Mg ₂ TiO ₄ -SChXCtLt may be up to several μm. The physical properties of the layer depend in part on the selected composition. Purely a pure Mg ₂ ^f Ui0 ₄ layer applies, for example: hardness to Mohs 6.5; Melting point 1840 ^° C .; Transparency for visible light nearly 100%; Refractive index for visible light 2.05 It is essential that the lattice parameter of the layer can vary depending on the composition, eg for the solid solution Mg ₂ TiO ₄ -MgCr ₂ O ₄ between 0.834 nm and 0.844 nm the lattice parameter of the layer is exactly twice the size of the lattice parameter of the MgO (a = 0.4212 nm), ie the interface of the ZSK is then an exactly coherent one.

The inventive method combines any suitable method for depositing a thin layer of TiOp (or of TiOp and another metal oxide which together with MgO forms the other component of the above solid solution) with a topotactic plague reaction occurring simultaneously with the deposition between the in Deposition TiOg (or TiOg and the other oxide) and the single crystal MgO substrate.

For this purpose, a flat, clean surface on the MgO crystal or a monocrystalline MgO layer with a flat, clean surface is first produced in a known manner. After adjusting the remaining process conditions of the selected separator (such as residual gas or atomizing gas pressure), this surface is heated to the temperature T. Then, the TiOp (or de, s TiOo and the other above oxide) with the Absehe tion rate R deposited on this surface. The quantities T and R must be chosen so that a topotactic solid-state reaction can take place between the deposited TiOp (or the deposited oxides) and the MgO, ie a reaction with partial or complete conservation of the crystal lattice of the MgO. In this way, a perfectly oriented, build-up rare layer is created. Since the proceeding reaction is a solid-state reaction, the properties of the Mg ₂ TiO, (or the above solid solution) in terms of its melting or vaporization equilibrium irrelevant, so that on the one hand, the reaction temperature T v, <may be lower , than the melting temperature of the 1.Ig ₂ TiO. and secondly, the incongruity of melting and evaporating the Mg ₂ TiO, which does not adversely affect the stoichiometry of the layer. The necessary to maintain the reaction by diffusion concentration gradient of TiO (or the above oxides) in Mg ₂ TiO. (or in the above solid solution), which sets itself, represents a relatively small disturbance of the stoichiometry of the layer.

The absence of the thickness R and an equivalent layer thickness 2T, which would have the layer of TiO ₂ , if no reaction with the MgO occurred, are measured in a known manner during the process. The thickness d of the resulting MgpTiO.-layer can be calculated from the measured equivalent layer thickness d as follows:

where N .. jUo - the number of formula units per unit cell for TiO ₂ or

^V 1 * ^V 3 ~ volume of the elementary metal of TiO ₂ or Mg ₂ TiO ₄

The same procedure is followed when the layer consists of a solid solution of Mg ₂ TiO. should exist. The process is continued until the required thickness d is reached and then terminated by interrupting the separation process and stopping the reaction.

1st embodiment

A two-layered body (ZSK) is produced, which consists of a MgO monocrystal and a (001) -oriented Mg ₂ TiO.-layer with the quality features mentioned above. For the Miller indices of the adhesion plane and the lattice directions lying in it, the following applies:

As a deposition method, the electron beam evaporation is selected in a high vacuum. On a MgO crystal (QO1) is generated -surface column, which is then heated in a substrate heater to 110o C ^0. "When Abscheidege speed R = 0.1 nm / s · chosen It runs the topotactic Pestkörperreaktion

from, in compliance with o.a. Relationships between the Miller indices.

The process is terminated after reaching the thickness 1 / um.

2 «embodiment

A ZSK is made which consists of a MgO-E and has a (001) -oriented layer consisting of the solid solution 0.8. (Mg ₂ TiO ₄ ) + 0.2. (MgCr ₂ O ₄ ) exists. For the cleavage plane and the intergrowth plane, the relationships in execution in Game 1 apply. As a cleavage, η, the e Ie ktrone ns trahlve rdanipfe η is selected in a high vacuum from two independent vaporizers. From the one evaporator TiO ₂ is evaporated from the other Cr ₂ Oo, in such a ratio of the evaporation rates that the substrate is a molar ratio of TiO ₂ : Cr ₂ Oo = 4ϊ1 present. The topotactic solid-state reaction occurs 9 MgO + 4 TiO ₂ + Cr ₂ O ₃ - * 5 {0.8 (Mg ₂ Ti0 ₄ ) +0.2 (MgCr ₂ 0 ₄ )}

in accordance with the relations between the Miller indices mentioned in the 1st embodiment. The process is terminated after reaching the thickness 0.5 / um.

Claims (4)

Two-layer body consisting of a monocrystalline substrate and a monocrystalline layer which has grown well-oriented to the substrate, characterized in that the substrate consists of magnesium oxide MgO and the layer of magnesium ortho-titanate consists · Two-piece body according to item 1, characterized in that the mutual orientation of the crystal lattices of the Mg ₂ TiO ₂ layer and the MgO substrate is determined by the following relations between the Miller indices of the frequency domain and the lattice directions contained therein: I! 3 »two-layer body according to item 2, characterized in that the quantities!, JjkjUjVjW take the following values: i = j = v = w = 0; k = u = 1 · 4 × 8-layered body according to points 1, 2 or 3, characterized in that the layer consists of a solid solution instead of Mg ₂ TiO ₄ , of which one component is Mg ₂ TiO ₄ and the other component of which is another magnesium-containing oxidic compound. 5 · two-layer body according to item 4, characterized in that the other magnesium-containing oxide compound is one or more of the following compounds: MgAl ₂ O ₄ , MgFe ₂ O ₄ , MgGr ₂ O ₄ , MgO. 6 · two-layer body according to item 4 or 5, characterized in that the molar ratio of the components of the solid solution is chosen such that the difference between the double gate of the MgO substrate and the Gitterpararneter the layer has a very specific size, in particular to zero. 7 · two-layer body according to item 1 to 6, characterized in that the layer is doped by life tall ions. 8 · two-layer body according to item 7, characterized in that these metal ions are either Cr ions or Mn ions. 9. two-layer body according to item 1 to 8, characterized in that a crystalline elces polycrystalline MgO body is used as a single-crystalline MgO Sübstrat. 10. two-layer body according to item 1 to 9 »characterized in that the two-layer body is part of a multi-layer body. 11. A process for the preparation of the two-layer body according to item 1 to 10, characterized in that the layer is formed by a topotactic Pestkörperreaktion simultaneously with the deposition of TiO ₂ (or of the TiO ₂ and the other necessary to form the solid solution metal oxides ), the deposition of the TiO ₂ (or of the TiO ₂ and the other necessary metal oxides) is carried out by a known or other method and the topotactic plague reaction between the MgO on the one hand and the deposited TiO ₂ ( or the TiO ₂ iHid the other necessary oxides) takes place on the other hand. 12. The method according to item 11, characterized in that the method is used to produce such a two-layer body whose layer component consists of a multicomponent oxidic compound which can be produced by a topotactic plague reaction, of which one outgrowth product is the substrate Component of the two-layer body is _f wherein the layer component or the substrate component or both consist of other oxidic compounds than those listed in points 1 to 10.