JP2001353402A - Method for growing crystal and functional element device using the crystal obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing crystal by which a good-quality large crystal can be made to grow at the temperature far lower than the melting point or the boiling point of the crystal even from such a material as is not dissolved in usual liquid solvent at room temperatures and is apt to be decomposed at the melting point or the vaporizing point and to provide a functional element device using the crystal obtained by this crystal growing method. SOLUTION: This method for growing crystal comprises an initial crystallization step and a recrystallization step. In the initial crystallization step, a crystal raw material is dissolved by heating a melting solvent, which is solid at the room temperature and the melting point of which is lower than that of the objective crystal, to prepare the solution and the objective crystal is then made to grow by supersaturating the objective crystal component in the solution. In the recrystallization step, which is executed once or repeated several times, the objective crystal is obtained by recrystallization namely by supersaturating the objective crystal component in the solution, keeping it in an unsaturated state and then supersaturating it again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crystal growth method suitable for growing organic crystals, such as polycyclic aromatic compounds, which are dissolved in a molten solvent and are easily decomposed and degraded at a dissolution temperature or a vaporization temperature, and The present invention relates to a functional element device using a crystal obtained thereby.

[0002]

2. Description of the Related Art Since an inorganic crystal has a high decomposition temperature, a flux method in which a crystal raw material is dissolved at a high temperature using a flux and a crystal is grown in a melt is known. This method is a method of growing a crystal using a difference in solubility of a target crystal due to a temperature change. The example PbO, PbF _2, KCl-N
It grows inorganic crystals such as barium titanate, ferrite and ruby using a flux such as aCl. The melting points of these fluxes are close to 900 ° C. Since this melting point is a temperature at which most organic crystals are decomposed, this method cannot be applied to the growth of organic crystals.

[0003] Further, a vapor phase growth method is known in which a crystal raw material is accommodated in a closed container and heated and vaporized, while a part of the container is cooled to precipitate crystals. In general, this method can obtain a high-quality single crystal with few defects. However, it is necessary to evacuate the inside of the container to a high vacuum or replace it with an inert gas. The crystallization efficiency is poor. Further, this method cannot be applied to a crystal raw material that is difficult to vaporize or a substance whose vaporization temperature is close to the decomposition temperature of the crystal.
Therefore, this method is not suitable for growing an organic crystal which is easily decomposed and deteriorated at a relatively low temperature.

Further, a crystal pulling method in which a crystal raw material is heated and melted, and a seed crystal is immersed in a melt and pulled up, or a crystal raw material is melted in a growth vessel, and then one end of the vessel is cooled to form a growth nucleus. There is a method of cooling and solidifying the melt while maintaining the temperature gradient in that part, but it is difficult to apply this method to the growth of organic crystals that are easily decomposed and degraded by heating and melting. It was difficult to control the temperature and pull up the seed crystal, and it was extremely difficult to obtain a good quality crystal.

[0005] Therefore, generally, a crystal raw material is dissolved in a liquid solvent at room temperature while heating, and then gradually cooled to precipitate crystals by utilizing the difference in solubility depending on the temperature. The recrystallization method used has been employed. This method is suitable for growing organic crystals because crystals can be precipitated at a temperature much lower than the melting temperature or sublimation temperature of the target crystal. However, during the growth process, impurities and solvent components of the solvent are taken into the crystal, which may cause crystal defects and distortion. Further, there is no suitable solvent depending on the kind of the organic crystal, and there are many cases where the above method cannot be adopted.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and solves the above problem even for substances which do not dissolve in ordinary liquid solvents at room temperature and are easily decomposed at the melting temperature or vaporization temperature. An object of the present invention is to provide a crystal growth method that can be grown at a much lower temperature than that and can produce a large crystal with good quality, and a functional device using the crystal obtained by the method.

[0007]

The above object is achieved by the following means. That is, the present invention provides: (1) using a molten solvent that is solid at room temperature and has a lower melting point than the target crystal, filling the crystal with the crystal raw material in a growth vessel, heating the molten material, and dissolving the crystal raw material in the molten solvent; After preparing the solution, the target crystal component in the solution is supersaturated, and an initial crystal growth step of growing the target crystal, and the target crystal component in the solution is supersaturated,
The target crystal component of the solution is less than saturation, the target crystal component of the solution is again supersaturated, and a crystal regrowth step of regrowing the grown crystal, the crystal regrowth step, A crystal growth method, which is performed once or more times. (2) using, as the molten solvent, one that crystallizes before the target crystal, crystallizes at least a part of the molten solvent in the solution, and forms a supersaturated region of the target crystal component in the solution; An initial crystal growth step of growing a target crystal, and heating the crystallized molten solvent to a molten state to make the target crystal component in the solution less than saturated, and again the molten solvent in the solution (1) crystallizing at least a portion of the target crystal, forming a supersaturated region of the target crystal component in the solution, and regrowing the target crystal. Crystal growth method. (3) In the initial crystal growth step and the crystal regrowth step,
The growth vessel is placed in a temperature gradient furnace such that one end is located in the high-temperature area and the other end is located in the low-temperature area, and the molten solvent in the solution is crystallized from one end on the low-temperature area side. The method according to (2), wherein a supersaturated region of the target crystal component is formed in the solution on the side. (4) The crystal growth method according to (3), wherein the temperature is gradually cooled at a cooling rate of 10 ° C./h or less while maintaining the temperature gradient in the temperature gradient furnace. (5) In the initial crystal growth step and the crystal regrowth step,
By disposing the entire growth vessel in a high-temperature region of a heating furnace and moving the growth container relatively to the heating furnace, the growth vessel is positioned in a low-temperature region of the heating furnace, and the The crystal growth method according to (2), wherein the molten solvent is crystallized to form a supersaturated region of a target crystal component in the solution. (6) The relative moving speed between the growth vessel and the heating furnace is:
The crystal growth method according to the above (5), wherein the crystal growth rate is 10 mm / min or less. (7) In the initial crystal growth step and the crystal regrowth step,
(1) The crystal growth method according to (1), wherein an easily evaporable molten solvent is used, the molten solvent is evaporated, and a target crystal component in the solution is relatively supersaturated. (8) In the initial crystal growth step and the crystal regrowth step,
The crystal growth method according to (7), wherein a closed type is used as the growth vessel, and the evaporated molten solvent is precipitated and solidified in the growth vessel. (9) In the crystal regrowth step, the deposited and solidified molten solvent is heated to be in a molten state, returned to the solution, and brought into a state where the target crystal component in the solution is less than saturated. The crystal growth method according to the above (8).

(10) The method according to any one of (1) to (9), wherein the crystal of the molten solvent is dissolved at room temperature using a liquid solvent, and the target crystal after crystal growth is recovered. 3. The crystal growth method according to item 1. (11) The crystal growth method according to any one of (1) to (10), wherein the target crystal is an organic crystal. (12) The crystal growth method according to (11), wherein the target crystal is a polycyclic aromatic compound. (13) The crystal growth method according to any one of (1) to (12), wherein the melting point of the molten solvent is in a range of 30 to 500 ° C. at normal pressure. (14) The crystal growth method according to (13), wherein the molten solvent is a polycyclic aromatic compound. (15) A semiconductor film formed using a target crystal obtained by the crystal growth method according to any one of (1) to (14) as a raw material, and a plurality of electrodes connected to the semiconductor film. A functional element device, comprising: (16) A semiconductor film comprising the target crystal itself obtained by the crystal growth method according to any one of (1) to (14), and a plurality of electrodes connected to the semiconductor film Functional element device characterized by the following.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The crystal growth method of the present invention uses a molten solvent which is solid at room temperature and has a lower melting point than the target crystal,
After filling the growth vessel with the crystal raw material and dissolving the crystal raw material in the molten solvent heated and melted to prepare a solution, the target crystal component in the solution is supersaturated to grow the target crystal. After the initial crystal growth step and the target crystal component in the solution are supersaturated, the target crystal component in the solution is brought to a state of less than saturation, the target crystal component in the solution is supersaturated again, and the grown crystal is And a crystal regrowth step of performing regrowth, wherein the crystal regrowth step is performed once or more than once. In this method, even for a substance that does not dissolve in a normal solvent that is liquid at room temperature and is easily decomposed at the melting temperature or vaporization temperature, crystals can be grown at a temperature much lower than the melting point or boiling point of the substance, By repeating the crystal regrowth step once or a plurality of times, high quality and large crystals can be manufactured. Further, the obtained target crystal tends to be a large single crystal. Hereinafter, this will be described in detail with reference to the drawings.

In the crystal growth method of the present invention, a target crystal component in a solution can be easily supersaturated in an initial crystal growth step and a crystal regrowth step by using a molten solvent which crystallizes prior to a target crystal. Can be Specifically, as the initial crystal growth step, at least a part of the molten solvent in the solution is crystallized, and a supersaturated region of a target crystal component is formed in the solution, so that the target crystal can be grown. . Further, as a crystal regrowth step, the crystallized molten solvent is heated to a molten state to bring the target crystal component in the solution to a state of less than saturation, and at least a part of the molten solvent in the solution again. Is crystallized to form a supersaturated region of the target crystal component in the solution, and the target crystal can be regrown. This method is particularly effective when the target crystal is a plate-like crystal system such as a polycyclic aromatic compound, and the molten solvent is also selected from a plate-like crystal system. Is a method suitable for obtaining large crystals of good quality.

In the crystal growth method of the present invention, a supersaturated region of the target crystal component can be formed in the solution by crystallizing the molten solvent prior to the target crystal. In the initial crystal growth step and the crystal regrowth step, the growth vessel is placed in a temperature gradient furnace such that one end is located in the high-temperature area and the other end is located in the low-temperature area, and the solution is placed at one end on the low-temperature area side. The molten solvent in the crystallization can be crystallized to form a supersaturated region of the target crystal component in the solution on the high temperature region side. Further, by disposing the entire growth vessel in a high-temperature area of a heating furnace and moving the growth vessel relatively to the heating furnace, the growth vessel is positioned in a low-temperature area of the heating furnace, and the The crystallization of the molten solvent in the above can form a supersaturated region of the target crystal component in the solution. In this case, the low temperature region may be the same as the room temperature. By moving the growth container out of the heating furnace, the growth container is located in the low temperature region of the heating furnace.

As a crystal growth method using a molten solvent that crystallizes prior to the target crystal, specifically, for example, a crystal growth method as shown in FIGS. 1 and 2 can be mentioned. FIG. 1 is an explanatory diagram showing an example of the crystal growth method of the present invention using a molten solvent that crystallizes prior to a target crystal. The crystal raw material and the molten solvent are mixed and housed in an ampoule (growth vessel) and then sealed. The inside of the growth vessel may be evacuated or purged with an inert gas and then sealed. Next, the ampoule is set in a vertical temperature gradient furnace so that the lower part is located in the high temperature area (TH) and the upper part is located in the low temperature area (TL), and the whole is heated and the crystal raw material is first melted with a molten solvent. Dissolve completely. After setting the upper part to the crystallization temperature of the molten solvent and the lower part to the temperature at which the crystal raw material is dissolved by the molten solvent, the whole is gradually cooled at a constant cooling rate while maintaining the temperature gradient (preferably ΔT ≦ 10 ° C./h), the molten solvent is crystallized from the upper part (lower temperature side) of the ampoule, and a supersaturated area of the crystal component is formed in the solution of the lower part (higher temperature side) to precipitate and grow crystals ( Initial crystal growth step). By further cooling, all the molten solvent is crystallized. The size of the target crystal thus obtained is widely distributed from several tens of μm to several mm.

Therefore, the whole ampoule is heated again to melt the once crystallized molten solvent again, so that the target crystal having a small size is dissolved again in the molten solvent, while the target crystal having a large size is melted. Remains. From this state, the whole is gradually cooled again while maintaining the temperature gradient in the same manner as described above, whereby the molten solvent is crystallized from the upper part of the ampoule, and a supersaturated region of the target crystal component is formed in the solution below the ampoule and melted. The remaining large crystal is used as a growth nucleus to further grow the crystal (crystal regrowth step).

FIG. 2 is an explanatory view showing another example of the crystal growth method of the present invention using a molten solvent which crystallizes prior to the target crystal. As in the crystal growth method shown in FIG. 1, the crystal raw material and the molten solvent are mixed, housed in an ampoule (growth vessel), and then sealed. Next, the ampoule is set in a vertical heating furnace, and the whole is first heated to completely dissolve the crystal raw material with a molten solvent that has been melted. This vertical heating furnace is provided with a lifting mechanism (not shown) for lifting and lowering the ampule. The ampoule is gradually raised by this elevator (preferably at a rising speed of ≦ 10 mm / min), and the ampule is taken out of the heating furnace. In the present invention, since the ampoule needs to move relatively to the heating furnace, only the ampoule may be moved, only the heating furnace may be moved, or both may be moved. Is also good. Along with this, the low temperature (room temperature) portion in the ampoule increases from above, the molten solvent is crystallized in order from the low temperature portion (top), and a supersaturated region of the target crystal component is formed in the solution under the ampoule to form crystals. Precipitate and grow (initial crystal growth step). Then, the whole ampule is pulled out of the heating furnace, and all the molten solvent is crystallized. The size of the target crystal thus obtained is widely distributed from several tens of μm to several mm as in the crystal growth method shown in FIG.

Therefore, the ampoule is set again in the heating furnace, the whole is heated, and the molten solvent once crystallized is melted again. The large target crystal remains undissolved. From this state, the ampoule is gradually raised again by the elevator, and the ampule is taken out of the heating furnace. Along with this, the molten solvent is crystallized from the upper part of the ampoule, forming a supersaturated region of the target crystal component in the solution under the ampoule, and using the target crystal of large size remaining undissolved as the growth nucleus, making the crystal even larger Growing (crystal regrowth step).

In the crystal growth method of the present invention, by using a solvent that evaporates easily as the molten solvent, the target crystal component in the solution can be easily supersaturated in the initial crystal growth step and the crystal regrowth step. . In particular,
In the initial crystal growth step and the crystal regrowth step, the molten solvent can be evaporated to make the target crystal component in the solution relatively supersaturated. At this time, it is preferable to use a closed type as the growth vessel and deposit and solidify the evaporated molten solvent in the growth vessel. In this case, without adding a molten solvent, in the crystal regrowth step, the molten solvent precipitated and solidified in the growth vessel is heated to be in a molten state, returned to the solution, and returned to the solution. The crystal component can be brought into a state of less than saturation.

A specific example of the crystal growth method using such a readily evaporated molten solvent is the crystal growth method shown in FIG. FIG. 3 is an explanatory diagram showing an example of the crystal growth method of the present invention using a readily evaporated molten solvent. The mixture of the crystal raw material and the molten solvent is housed in an ampoule and sealed. At this time, it is preferable that the inside of the growth container is evacuated and then sealed. Next, the lower part is in the high temperature region (T
The ampoule is set in a vertical temperature gradient furnace so that the upper part is located in the low temperature region (TL) in H), and the crystal raw material is completely dissolved by the molten solvent heated and melted. The lower part of the ampoule is kept at the temperature at which the molten solvent evaporates from the solution, while the upper part is the condensation of the molten solvent vapor (melting point).
By cooling to below the temperature, the molten solvent evaporated on the ampule is deposited and solidified (condensed). On the other hand, the amount of the molten solvent in the solution below the ampoule is reduced, and the target crystal component is supersaturated to precipitate and grow a crystal (initial crystal growth step). The size of the target crystal thus obtained is
Similar to the crystal growth method shown in FIGS. 1 and 2, the distribution ranges widely from several tens μm to several mm.

Therefore, the upper portion of the ampoule is heated to a temperature equal to or higher than the melting temperature of the molten solvent, and the molten solvent once deposited and solidified in the upper portion of the ampoule is melted again and returned to the lower portion of the ampoule. The state can be less than saturation. At this time, the target crystal having a small size is dissolved again in the molten solvent, while the target crystal having a large size remains undissolved. From this state, the amount of the molten solvent in the solution at the lower part of the ampoule is reduced by cooling the upper part to a temperature lower than the condensation (melting point) temperature of the vapor of the molten solvent, as described above,
The target crystal component is supersaturated, and the crystal having a large size remaining undissolved is used as a growth nucleus to grow the crystal further (crystal regrowth step).

In the crystal growth method shown in FIGS. 1 to 3, a series of crystal regrowth steps may be repeated as many times as there are no fine crystals. The ampoule may be open. In the case of an open system, the surface of the grown crystal may be oxidized or degraded by contact with the atmosphere. There is no need to seal. In the case of an open system, a molten solvent and a target crystal raw material can be added from the outside. In particular, in the case of the crystal growth method shown in FIG. 3, by adding a molten solvent, the target crystal component in the solution can be brought back to a state of less than saturation. In the case of the crystal growth method shown in FIGS. 1 and 2, a horizontal furnace can also be used, and the temperature gradient in the temperature gradient furnace in FIG. 1 may be inverted. After the crystal has grown again, air cooling or rapid cooling may be performed.

The crystal growth method of the present invention is suitable for growing an organic crystal. In particular, it has solvent resistance that does not dissolve in general organic solvents, but has the property of dissolving in molten solvents, has a high sublimation temperature, and is suitable for crystal growth of organic compounds that are easily decomposed and degraded at the melting temperature or vaporization temperature. I have. For example, polycyclic aromatic compounds such as phthalocyanine-based compounds, perylene-based compounds, pyrene-based compounds, quinacridone-based compounds, squarium compounds, triphenylamine-based compounds, trisazo compounds, bisazo pigments, condensed aromatic-based pigments, and indico pigments Can be mentioned. Specifically, Cu
-Phthalocyanine, Ni-phthalocyanine, Mg-phthalocyanine, TiO-phthalocyanine, Al-phthalocyanine chloride, Fe-phthalocyanine, Al-quinolinade and the like. Also, tris (8-hydroxyquinolino) aluminum, N-N'-dimethylperylene-3,4,9,10-bis (dicarboximide)
Compounds known as organic semiconductor materials, such as, for example, are also preferred.

The type of the molten solvent is not particularly limited as long as it is solid at room temperature, dissolves the crystal raw material in a molten state, and has a lower melting point than the target crystal. Here, "solid at room temperature" indicates that the material is at least a solid under the use environment. Specifically, the melting point of the molten solvent is preferably from 30 to 500 ° C, more preferably from 50 to 350 ° C, and still more preferably from 100 to 300 ° C, depending on the kind of the target crystal. Furthermore, when selecting an easily crystallizable molten solvent, the amount of solvent in the molten state decreases as the molten solvent crystallizes prior to the target crystal, so that a supersaturated region of the target crystal component is easily formed in the solution. can do. Also, when selecting a solvent that easily evaporates as the molten solvent, by evaporating the molten solvent from the solution in which the crystal raw material is dissolved,
The amount of the molten solvent in the solution can be reduced, the concentration of the target crystal component can be increased, and the concentration can be easily supersaturated. Here, the term “melt solvent that easily evaporates” refers to a solvent in which the vapor pressure of the molten solvent exceeds the pressure in the environment of use at the melting temperature of the molten solvent.

On the other hand, the molten solvent is preferably one in which the crystals of the molten solvent are easily dissolved by a liquid solvent at room temperature. When such a molten solvent is used, there is an advantage that after the crystal growth is completed, the target crystal can be easily recovered by dissolving only the molten solvent crystal with the solvent. In particular, in order to obtain an organic crystal such as a polycyclic aromatic compound as a target crystal, the melting point of the polycyclic aromatic compound having a melting point of room temperature or higher, preferably 30 to 500 ° C, more preferably 50 to 350 ° C. It is preferred to use a molten solvent. Specifically, naphthalene, anthracene, tetracene, pentacene, biphenyl, terphenyl, pyrene,
Perylene, phenanthrene, phenanthrolen and the like can be used. Unlike these crystallization methods using a common organic solvent that is liquid at room temperature,
Since the solvent molecule has a relatively large structure, the solvent molecule is not taken into the target crystal, and a high-purity crystal with few defects can be obtained.

At a suitable temperature equal to or higher than the melting point of the molten solvent, the amount of the molten solvent needs to be slightly larger than the amount capable of completely dissolving the raw material crystals, ie, the amount of the molten solvent that saturates the target crystal component. At room temperature, a solid molten solvent is heated to become a liquid, and when dissolving the raw material crystals, if some of the raw material crystals remain as solids, they become nuclei and many microcrystals are precipitated, so large crystals can be obtained. It becomes difficult.

In the crystal growth method of the present invention, the temperature at which the crystal raw material is dissolved in the molten solvent can be appropriately selected within a range not lower than the melting point of the molten solvent and less than the decomposition temperature of the target crystal. Unlike the flux method, not only the crystal is precipitated using the difference in solubility depending on the temperature, but also, for example, the molten solvent itself is cooled and crystallized in a part of the growth vessel, Crystals can be grown in a supersaturated state by increasing the concentration of the target crystal component by reducing the amount of the molten solvent, and crystals whose solubility does not change significantly with temperature can be grown by the present invention.

More specifically, for example, in the crystal growth method shown in FIG. 1, the temperature distribution in the growth vessel initially has a relatively lower portion (supersaturated region of the target crystal component in the growth vessel) which is the melting temperature of the crystal raw material. At an elevated temperature, the upper portion (the site of the growth vessel to crystallize the molten solvent) is at a relatively low temperature where the molten solvent is precipitated. Thereafter, the entire growth vessel is gradually cooled to promote the precipitation (crystallization) of the molten solvent, thereby reducing the amount of the molten solvent in the solution and increasing the concentration of the target crystal component in the lower solution. At that time, by applying a steep temperature gradient to the portion near the bottom of the growth vessel, most of the molten solvent is crystallized, and the concentration of the target crystal component in the solution at the bottom is further increased to promote crystal growth. Is also good. In order to obtain this steep temperature gradient, the bottom of the growth vessel may be made nearly flat and heated from the bottom.

The temperature difference between the bottom and the top of the growth vessel is
Although depending on the type of the molten solvent, a range of 5 to 500C, preferably 10 to 100C is appropriate. When the temperature difference is small, the entire system may be solidified almost simultaneously in the process of gradually cooling the growth vessel, it is difficult to adjust the target crystal component to supersaturation, and it is difficult to grow the target crystal in the crystal of the molten solvent. If not, there is a risk of solidification with the solvent.

In the crystal growth method of the present invention, when a molten solvent that crystallizes prior to the target crystal is used, any mechanism for gradually cooling the growth vessel may be used, and the slow cooling rate is appropriately determined according to the type of the target crystal. The temperature may be selected, for example, 10 ° C./h or less, preferably 2 ° C./h or less. In particular, in the crystal growth method shown in FIG. 1, it is preferable to gradually cool at 10 ° C./h or less, preferably 2 ° C./h or less, while maintaining the temperature gradient in the temperature gradient furnace. In the crystal growth method shown in FIG. 2, the growth vessel is moved relatively to the heating furnace (by pulling it up from the heating furnace) to gradually cool from the upper part of the growth vessel. It may be appropriately selected depending on the type of the target crystal. If the moving speed is too fast, the crystallization of the molten solvent proceeds rapidly, and the ungrown target crystal raw material may be taken into the molten solvent crystal solid. Therefore,
The relative movement speed between the growth vessel and the heating furnace is, for example, 10 mm
/ Min or less, preferably 1 mm / min or less.

In the crystal growth method of the present invention, when a molten solvent that is easily evaporated is used, as in the crystal growth method shown in FIG. Temperature difference (temperature melting point) and the upper low temperature region (precipitation and solidification temperature of the molten solvent)
It is preferable to maintain the temperature of the entire furnace. The temperature difference of this temperature gradient furnace depends on the type of molten solvent,
The temperature is preferably 1 to 100 ° C, more preferably 1 to 100 ° C.
-10 ° C. If this temperature difference (temperature gradient) is too large, the process of evaporating in the high temperature region and precipitating and solidifying in the low temperature region progresses rapidly, so that the amount of the molten solvent in the molten state decreases rapidly, and as a result, the molten solvent There is a possibility that the concentration of the target crystal component therein may increase rapidly. When such a rapid increase in concentration occurs, polynucleus formation of the target crystal is likely to occur, and it is difficult to obtain a large crystal. Therefore, from the viewpoint of slowly evaporating the molten solvent, it is preferable to maintain a temperature difference (temperature gradient) within the above range and maintain the temperature of the entire furnace.

In the crystal growth method of the present invention, the growth vessel is preferably a sealed tube because the molten solvent itself may evaporate. Further, a container that is easily broken, such as a glass ampule or a quartz ampule, is preferable. This is because the target crystal can be taken out in a state where the target crystal is taken in the solid molten solvent by breaking the ampoule.

The method of separating and recovering the target crystal from the molten solvent crystal taken out of the growth vessel may be any method that does not break the crystal. The crystal of the solidified molten solvent may be mechanically divided and the target crystal taken therein may be counted, or the solvent may be used at room temperature in a liquid (solvent that preferentially dissolves the crystal of the molten solvent). The crystal may be dissolved and the target crystal after crystal growth may be recovered.
The latter method has the advantages that when the target crystal is taken out, damage to the crystal can be minimized and the surface of the target crystal can be cleaned at the same time. Here, the term "liquid at room temperature" indicates that the liquid is at least a liquid under the use environment.

As described above, according to the present invention, it is possible to obtain a very large target crystal having a very low purity and a high purity as compared with the conventional crystallization method using a solvent. In addition, since the target crystal such as phthalocyanine is conventionally manufactured by an acid pasting method or the like, it cannot be avoided that an acid is mixed into the crystal. Although there was a problem that the copying characteristics could not be provided, the target crystals obtained by the crystal growth method of the present invention did not contain an acid and were of high purity, so that the electronic copying characteristics such as photosensitivity, chargeability, and dark decay were excellent. This is advantageous for producing a single-layer or multilayer OPC photoconductor. In addition, a high-quality semiconductor film can be obtained by forming a film using the obtained target crystal as a raw material.
Since these can be used as semiconductors, it is advantageous for easily and inexpensively producing a high-quality functional device.

(Functional Device) The functional device of the present invention comprises a semiconductor film formed from a target crystal obtained by the crystal growth method of the present invention as a raw material or a semiconductor comprising the target crystal itself and the semiconductor film or the semiconductor film. A plurality of electrodes connected to the semiconductor. The functional device device of the present invention is not particularly limited as long as the target crystal obtained by the crystal growth method of the present invention is used, and may have various configurations such as a semiconductor device and a thin film transistor.

In the functional device device of the present invention, as described above, since the target crystal obtained by the crystal growth method of the present invention is a high-quality and large crystal, a high-quality semiconductor film can be formed by using this as a raw material. The target crystal itself can be used as a semiconductor by molding as it is or by forming it into a desired shape, so that it can be easily produced, and is inexpensive and of high quality. As described above, since the target crystal obtained by the crystal growth method of the present invention is large, it can be used not only as a raw material but also the target crystal itself. It is particularly preferable that the obtained target crystal is a large single crystal.

Hereinafter, the functional device of the present invention will be specifically described. FIG. 4 is a schematic cross-sectional view of a field-effect transistor which is an example of the functional device according to the present invention. FIG.
In the field-effect transistor shown in FIG. 1A, after a source electrode 2 and a drain electrode 3 are formed on a substrate 1, a semiconductor film 4 is formed thereon. An insulating film 5 is formed on the semiconductor film 4, and a gate electrode 6 for electrolytic control is further formed on the insulating film 5 to obtain a final thin film transistor. Here, the semiconductor film 4 is formed by using the target crystal obtained by the crystal growth method of the present invention as a raw material and depositing it on the substrate 1 by the film forming method. Such a film formation method is preferable because the orientation of the target crystal (eg, organic molecule) on the substrate can be controlled by selecting an appropriate substrate surface.

In the field effect transistor shown in FIG. 4B, a source electrode 2 and a drain electrode 3 are formed on a semiconductor 7. After that, an insulating film 5 is formed on the semiconductor 7, the source electrode 2 and the drain electrode 3, and a gate electrode 6 for electrolytic control is formed on the insulating film 5 to obtain a final thin film transistor. Here, the semiconductor 7 is obtained by shaping the target crystal obtained by the crystal growth method of the present invention as it is or in a desired shape. In this case, the semiconductor 7 also plays the role of a substrate. The field effect transistor shown in FIG. 4B has a semiconductor film formed thereon as shown in FIG.
It has characteristics equivalent to those of the field-effect transistor shown in FIG.

In FIG. 4, the substrate 1 is made of glass,
Any material such as plastic and mica can be used, and it is preferable to select a substrate in which the target crystal exhibits good orientation. As the source electrode 2, the drain electrode 3, and the gate electrode 6, a conductive substance such as gold, platinum, chromium, palladium, aluminum, tin oxide, or ITO can be used.
These materials can be formed by the above film formation method. As the insulating film 5, an inorganic insulating film such as silicon nitride or silicon oxide, or an organic insulating film such as polyamide resin can be used.

[0037]

The present invention will be described below with reference to examples. “Parts” in the examples means “parts by weight”. (Example 1) 2 parts of anthracene (Aldrich) as a molten solvent and Cu-phthalocyanine (Wako Pure Chemical Industries)
0.01 part was mixed and sealed in a glass ampoule, and placed in a vertical temperature gradient furnace to set the lower part to 220 ° C and the upper part to 210 ° C.
° C to completely dissolve the Cu-phthalocyanine. Thereafter, the whole ampoule was gradually cooled at a cooling rate of 2 ° C./h to grow a crystal. Then, the whole ampoule was heated again, the lower part was heated to 220 ° C., and the upper part was heated to 210 ° C., and immediately thereafter, the whole ampoule was gradually cooled at a cooling rate of 2 ° C./h to grow larger crystals. After cooling to room temperature,
The glass ampoule was cracked, the contents were taken out, and the anthracene was dissolved with acetone. As a result, about 10 mm length ×
0.009 parts of a red-purple Cu-phthalocyanine single crystal having a width of 0.2 mm and a thickness of 0.3 mm was obtained.

Comparative Example 1 For comparison, 3 parts of Cu-phthalocyanine (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in 60 parts of concentrated sulfuric acid at 0 ° C., and then dropped into 450 parts of distilled water at 5 ° C. Crystals were deposited. The obtained crystals were sufficiently washed with dilute aqueous ammonia and distilled water, and then dried to obtain 2.5 parts of Cu-phthalocyanine crystals.

(Evaluation) Cu obtained in Example 1 and Comparative Example 1
-A photosensitive layer plate was prepared using a phthalocyanine crystal by the following method. That is, the crystals were ground in an automatic mortar for 5.5 hours, and the resulting Cu-phthalocyanine crystal powder was used in a mortar.
One part is polybutyral (Sekisui Chemical Co., Ltd .: Eslec BM
-S) 1 part and 10 parts of cyclohexanone were mixed, and the mixture was treated with glass beads for 1 hour using a pent shaker to prepare a coating liquid in which the crystal powder was dispersed. Next, a conductive aluminum substrate is dipped in a coating solution and coated,
The resultant was dried by heating at 0 ° C. for 5 minutes to produce a photosensitive layer plate having a thickness of about 20 μm.

A positive charge was applied to the photosensitive layer plate by a corona discharge with a +5 kV corona gap of 10 mm to the photosensitive layer surface for 30 seconds, and after the corona discharge was stopped for 30 seconds, a 3000 ° K tungsten light source was used. 20 Lu
Exposure at x illuminance, maximum surface charge, dark decay rate of potential 30 seconds after potential 5 seconds after completion of charging, and surface potential 10% of potential immediately before exposure The irradiation dose required to reduce was measured.

As a result, the photosensitive layer plate of Example 1 showed good electrophotographic characteristics with a surface charge of 750 V, a darkening and decay rate of 19.5%, and an irradiation of 70 Lux / sec. On the other hand, the surface charge amount of the photosensitive layer plate of Comparative Example 1 was 550.
V, the dark decay rate is 40.0%, and the irradiation amount is 78 Lux / se.
c and a decrease in electrophotographic properties. This is C in Comparative Example 1.
This is probably because sulfuric acid as a solvent was mixed in the u-phthalocyanine crystal.

Example 2 2 parts of pyrene (manufactured by Aldrich) as a molten solvent and tris (8-hydroxyquinolino)
Aluminum (Aldrich, Alq3) 0.01
The mixture was sealed in a glass ampoule, placed in a vertical temperature gradient furnace, and heated to 160 ° C for the lower part and 150 ° C for the upper part to completely dissolve tris (8-hydroxyquinolino) aluminum. did. Thereafter, the whole ampoule was gradually cooled at a cooling rate of 2 ° C./h to grow a crystal. Then, the whole ampoule is heated again, the lower part is heated to 160 ° C. and the upper part is heated to 150 ° C., and then the whole ampoule is immediately cooled at a cooling rate of 2 ° C.
C./h was gradually cooled to grow larger crystals. After cooling to room temperature, the glass ampule was cracked, the contents were taken out, and pyrene was dissolved with n-hexane. As a result, 0.009 parts of a yellow single crystal of tris (8-hydroxyquinolino) aluminum having a length of about 12 mm, a width of 0.06 mm and a thickness of 0.06 mm were obtained.

(Example 3) 2 parts of anthracene (manufactured by Aldrich) as a molten solvent and N, N'-dimethylperylene-3,4,9,10-bis (dicarboximide) (B
ASF, DM-PBDCI) 0.01 part was mixed and sealed in a glass ampoule, placed in a vertical temperature gradient furnace and heated to 220 ° C. for the lower part and 210 ° C. for the upper part, and N, N'-dimethylperylene-3,4,9,10-bis (dicarboximide) was completely dissolved. Thereafter, the whole ampoule was gradually cooled at a cooling rate of 2 ° C./h to grow a crystal. Thereafter, the whole ampoule was heated again, the lower part was heated to 220 ° C. and the upper part was heated to 210 ° C., and immediately thereafter, the whole ampoule was gradually cooled at a cooling rate of 2 ° C./h to grow larger crystals. After cooling to room temperature, the glass ampule was cracked, the contents were taken out and the anthracene was dissolved with acetone. As a result, about 8mm length x 0.2mm width x 0.1m
m thick red N, N'-dimethylperylene-3,4,9,
0.009 parts of 10-bis (dicarboximide) single crystal was obtained.

Example 4 On the mica substrate, 200
Angstrom source and drain electrodes were formed of gold. Under the vacuum deposition of 1399.65 Pa (10.5 torr), the Cu-phthalocyanine single crystal obtained in Example 1 was deposited as a raw material to a thickness of 0.1 μm. It was confirmed that the deposited film was highly oriented in the vertical direction on the mica substrate. Then 15w of poly pullulan
A t% acetonitrile solution was spin-coated on the substrate to form an insulating film. After the insulating film was dried, a gate electrode was formed using gold to obtain a staggered thin film transistor. The carrier mobility of the obtained thin film transistor is 1 ×
10.1 cm ² / V · sec, and it was confirmed that the thin film transistor functioned.

[0045]

As described above, according to the present invention, it is possible to grow even a substance which is difficult to vaporize and is easily decomposed at the melting temperature or the vaporization temperature, such as an organic crystal, at a temperature much lower than the melting point or boiling point of the crystal. Can be. Then, unlike the conventional recrystallization method, a large crystal with high purity can be obtained without incorporating solvent molecules into the crystal. In particular, as for a polycyclic aromatic compound crystal such as phthalocyanine, a crystal having excellent electrophotographic properties can be obtained by using a polycyclic aromatic compound such as naphthalene as a melting solvent. Also,
Similarly, these polycyclic aromatic compound crystals such as phthalocyanine are used as semiconductor films in functional device devices.
High quality crystals can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one example of a crystal growth method of the present invention using a molten solvent that crystallizes prior to a target crystal.

FIG. 2 is an explanatory view showing another example of the crystal growth method of the present invention using a molten solvent that crystallizes prior to a target crystal.

FIG. 3 is an explanatory view showing one example of the crystal growth method of the present invention using a readily evaporated molten solvent.

FIG. 4 is a schematic cross-sectional view of a field-effect transistor which is an example of a functional device according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 9/02 618 B01D 9/02 618A 620 620 625 625A 625Z C09B 67/48 C09B 67/48 Z 67/50 67/50 Z C30B 9/08 C30B 9/08 29/54 29/54 // C07D 487/22 C07D 487/22 (72) Inventor Okada Komasa 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. 72) Inventor Tatsuya Maruyama 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Masaaki Shimizu 430 Sakai Nakaicho, Ashigara-gun, Kanagawa Green Tech Naka Fuji Xerox Co., Ltd. F-term (reference) 4C050 PA14 4G077 AA02 BF10 CD04

Claims (16)

[Claims] 1. Using a molten solvent which is solid at room temperature and has a lower melting point than the target crystal, is charged into a growth vessel together with the crystal raw material, and heated to dissolve the crystal raw material in the molten solvent to prepare a solution. After the above, the target crystal component in the solution is supersaturated, and an initial crystal growth step of growing the target crystal, and after the target crystal component in the solution is supersaturated, the target crystal component of the solution is saturated. A crystal regrowth step in which the target crystal component of the solution is supersaturated again, and the grown crystal is regrown, wherein the crystal regrowth step is performed once or more than once. Crystal growth method. 2. A method for forming a supersaturated region of a target crystal component in the solution, wherein at least a part of the molten solvent in the solution is crystallized by using a material that crystallizes before the target crystal as the molten solvent. And an initial crystal growth step of growing a target crystal, and heating the crystallized molten solvent to a molten state to make the target crystal component in the solution less than saturated, and again in the solution in the solution. A crystal regrowth step of crystallizing at least a part of the molten solvent, forming a supersaturated region of the target crystal component in the solution, and regrowing the target crystal. The crystal growth method according to the above. 3. In the initial crystal growth step and the crystal regrowth step, the growth vessel is placed in a temperature gradient furnace such that one end is located in a high-temperature area and the other end is located in a low-temperature area. 3. The crystal growth method according to claim 2, wherein the molten solvent in the solution is crystallized from one end to form a supersaturated region of the target crystal component in the solution on the high temperature region side. 4. The crystal growth method according to claim 3, wherein the temperature is gradually cooled at a cooling rate of 10 ° C./h or less while maintaining the temperature gradient in the temperature gradient furnace. 5. In the initial crystal growth step and the crystal regrowth step, the entire growth vessel is placed in a high-temperature region of a heating furnace, and the growth vessel is moved relatively to the heating furnace to thereby form the growth vessel. 3. A method according to claim 2, wherein at least a part of the solution is located in a low temperature region of the heating furnace to crystallize the molten solvent in the solution to form a supersaturated region of a target crystal component in the solution. Crystal growth method. 6. The crystal growth method according to claim 5, wherein a relative moving speed between the growth vessel and the heating furnace is 10 mm / min or less. 7. In the initial crystal growth step and the crystal regrowth step, an evaporable solvent is used as the molten solvent,
2. The crystal growth method according to claim 1, wherein said molten solvent is evaporated to relatively supersaturate a target crystal component in said solution. 8. The method according to claim 7, wherein in the initial crystal growth step and the crystal regrowth step, a closed-type growth vessel is used, and the evaporated molten solvent is precipitated and solidified in the growth vessel. The crystal growth method according to the above. 9. In a crystal regrowth step, the deposited and solidified molten solvent is heated to a molten state,
9. The method of growing a crystal according to claim 8, wherein the target crystal component in the solution is returned to the solution to be less than saturated. 10. The crystal according to claim 1, wherein the crystal of the molten solvent is dissolved at room temperature using a liquid solvent, and the target crystal after crystal growth is recovered. Growth method. 11. The crystal growth method according to claim 1, wherein the target crystal is an organic crystal. 12. The method according to claim 11, wherein the target crystal is a polycyclic aromatic compound. 13. The melting point of the molten solvent is 30 to 5 at normal pressure.
The crystal growth method according to any one of claims 1 to 12, wherein the temperature is in the range of 00C. 14. The method according to claim 13, wherein the molten solvent is a polycyclic aromatic compound. 15. A semiconductor film formed by using a target crystal obtained by the crystal growth method according to claim 1 as a raw material, and a plurality of electrodes connected to the semiconductor film. A functional element device, comprising: 16. A semiconductor comprising a semiconductor made of a target crystal obtained by the crystal growth method according to claim 1, and a plurality of electrodes connected to the semiconductor. Functional device device.