JPS62143897A - Crystal deposition substrate for vapor-phase synthesis - Google Patents

Abstract

PURPOSE:To repeatedly produce a crystal free from flaws and cracks on a flexible graphite substrate for deposition of crystal, by heating the substrate in a reaction tube and supplying a raw material gas together with a carrier gas to the substrate. CONSTITUTION:Natural flaky graphite is expanded to a bulk density of about 0.003g/cm<3> by acid treatment and high-temperature treatment and the expanded graphite is compression molded to obtain a flexible graphite substrate 3 for crystal deposition to be used in a vapor-phase synthesis apparatus. A raw material gas (e.g. H2S gas and metallic Zn vapor) of a desired compound (e.g. ZnS crystal) is supplied together with a carrier gas (e.g. H2) from one end of a horizontally extended quartz reaction tube 1 through a raw material gas feeding nozzle 2 into the reaction tube 1. A synthesized compound is deposited on the flexible graphite substrate 3 heated with a heater 6 placed closely at the downstream side of said gas stream to obtain a compound crystal free from flaws and cracks.

Description

[Detailed description of the invention] (7) Technical field This invention relates to a crystal deposition substrate for vapor phase synthesis.

In the gas phase synthesis method, a gas containing the components of a desired compound is blown into a heated substrate in a reaction tube together with a carrier gas to synthesize the compound on the substrate.

The compound formed by the reaction is deposited on the substrate as a polycrystal. The carrier gas and the unreacted raw material gas become powder and adhere to the inside of the reaction tube on the downstream side of the substrate, or are exhausted by an exhaust device.

FIG. 1 is a longitudinal cross-sectional view of the vapor phase synthesizer i.

The reaction tube 1 is a horizontally long reaction container, and is made of, for example, a quartz tube.

From one end of the reaction tube 1, feed gas is fed into the reaction tube 1 by feed gas supply nozzles 2.2, .

Inside the reaction tube 1, a crystal deposition substrate 3 is provided immediately downstream of the source gas supply nozzle 2.2.

The synthesized compound 4 is deposited on the inner surface of the crystal deposition substrate 3. The compound that accumulates becomes polycrystalline. The crystal deposition substrate 3 is maintained at a higher temperature than the crystallization temperature by the heater 6 .

B) Prior art and its problems The crystal deposition substrate is a cylindrical body with a rectangular cross section. A compound formed by the reaction of the raw material gases is deposited on the inner surface of the cylindrical body.

Conventional crystal deposition substrates have used ordinary carbon plates.

Crystal deposition substrates were made from carbon by extrusion or stamping.

Carbon is stable against chemical reactions and has good heat resistance.

However, conventional crystal deposition substrates for vapor phase synthesis have the following drawbacks.

When the synthesis reaction is finished, the supply of raw material gas is stopped, the heater is turned off, the apparatus is cooled, and the deposited substrate is taken out.

However, there were cases where the synthesized crystals broke and cracks occurred.

The thermal expansion coefficients of the deposited substrate and the synthesized polycrystal are different.

Therefore, stress is generated between the crystal and the substrate as the crystal cools. As the stress increases, the crystal eventually cracks and some parts break.

It is thought that cracks and the like occur in the synthetic crystal due to such causes.

(1) Purpose It is an object of the present invention to provide a deposition substrate in which synthetic crystals are free from cracks and cracks.

B) Construction Instead of the usual carbon plate, in the present invention, the deposition substrate is made of flexible graphite.

Flexible graphite is made by subjecting natural scaly graphite to acid treatment and high temperature treatment to expand it to a density of about 0.003 g/Crn, and then compression processing and molding.

It has excellent properties such as heat resistance, corrosion resistance, flexibility, and high compression recovery rate.

Since it is graphite, it is naturally heat resistant and corrosion resistant. However, graphite does not have flexibility or compression recovery properties.

Because it is flexible graphite, it is flexible. Being flexible means that it is easily bent by external forces.

Compressibility means that even if it is compressed and bent, it can return to its original shape.

Flexible graphite is a new material.

Flexible graphite molded into a flat plate is commercially available under the trade names Nika Film, Nippon Carbon Co., Ltd. Permanent Foil, Toyo Sumitomo X(W), and can be easily obtained.

Shapes other than flat plates can be easily formed by press working.

It is also possible to form a cylindrical shape. It is also possible to form a dome shape.

The present invention constructs the deposition substrate from flexible graphite rather than graphite. Although the overall structure of the apparatus shown in FIG. 1 remains the same, the novel point is that the deposition substrate 3 is formed of a flexible substrate.

It is also possible to form a cylinder with a rectangular cross section by fixing four flat flexible graphite plates. Alternatively, the flexible graphite material may be formed into a rectangular tube.

(a) Function A gas containing the raw material for the crystal to be synthesized and a carrier gas are blown into the reaction tube 1 from the raw material gas supply nozzle 2.

The deposition substrate 3 made of flexible graphite has a cylindrical shape and is placed inside the reaction tube 1 . A heater 6 heats the deposition substrate 3. The temperature of the deposition substrate 3 is higher than the crystallization temperature.

The source gas reacts in the space inside the substrate 3, becomes solid, and is deposited on the substrate 3 as polycrystals.

Although it is called deposition, it does not mean that it is deposited only on the inner bottom surface of the inner surface of the deposition substrate 3. Compound crystals are deposited on all four sides: the top, sides, and bottom.

Since the substrate 3 has sufficient length, most of the raw material gas reacts within it. However, some parts remain unresponsive.

Unreacted raw material gas and carrier gas are extracted from the deposition substrate 3. Since the temperature in other parts of the reaction tube 1 is lower than the crystallization temperature, almost no reaction occurs and the reaction tube 1 is discharged as is from the exhaust pipe 5.

(To) Examples A ZnS crystal was synthesized using the apparatus of the present invention.

The raw material gases are H2S gas and metal Zn vapor.

The carrier gas is H2.

The inner diameter of the quartz reaction tube was 220 mm.

The deposition substrate was a cylindrical body with a square cross section of 120 x 201 m and a length of 1000 mm.

According to the present invention, ZnS was synthesized under the same conditions using a flexible graphite substrate and a conventional carbon substrate.

In the synthesis using a flexible graphite substrate, no cracks or cracks occurred in the ZnS crystal.

In synthesis using a carbon substrate, ZnS crystals are
It was broken into a mosaic pattern.

(1) Effects (1) Synthesized crystals do not have cracks or cracks.

Flexible graphite is highly flexible and has a high compression recovery rate. The synthesized crystal adheres closely to the flexible graphite substrate, and the crystal shrinks when cooled. Since flexible graphite is flexible, it contracts together with the crystal, and no strong stress is generated between the two.

Therefore, no cracks or cracks occur in the crystal during cooling.

Once the crystal is removed, the substrate returns to its original dimensions.

Can be used repeatedly.

(2) Heat resistant and corrosion resistant.

Since it is originally graphite, it is chemically stable. It also has high heat resistance in the absence of oxygen.

(3) Can be molded into various shapes by press working.

(4) There is no need to change other parts of the vapor phase synthesizer;
It can be applied directly to conventional equipment.

(5) ZnS, Zn5e, C:dTelCdS
, CdSe, Pb5e.

It can be used to synthesize polycrystals such as HgSe...

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a vapor phase synthesis apparatus that uses the deposition substrate of the present invention. 1...Reaction tube 2... Raw material gas supply nozzle 3...
・Crystal deposition substrate 4...Compound crystal 5...Exhaust pipe 6...Substrate heater inventor Shigetoji Kikuchi

Claims (1)

[Claims] 1. A crystal deposition substrate for vapor phase synthesis, which is a substrate on which crystals synthesized in a vapor phase synthesis apparatus are deposited, and is made of flexible graphite.