JPH08134442A - Accelerated phosphor material and infrared-visible conversion element prepared using the same - Google Patents

Abstract

PURPOSE: To obtain an accelerated phosphor excellent in long-term stability. CONSTITUTION: This accelerated phosphor comprises an alkaline earth chalcogenide crystal contg. at least one rare earth element, the surface of the crystal being covered with an alkaline earth fluoride compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photostimulable phosphor, an optical memory using the phosphor, and an infrared-visible conversion element.

[0002]

2. Description of the Related Art A light source for optical communication uses a band of 1.3 to 1.5 μm in consideration of loss of an optical fiber.
In order to handle such light that cannot be seen by the naked eye as information, an element that visualizes infrared light represented by a stimulated phosphor has been developed. Photostimulated luminescence is a phenomenon that has been known for a long time and is observed in many materials such as sulfide-based, alkali halide-based, and oxide-based materials. Among them, those based on alkaline earth chalcogenide crystals are well known. The principle of light emission of the stimulated phosphor will be briefly described with reference to FIG. As a phosphor material, a material in which a rare earth ion (Eu, Sm, Ce, etc.) is added as a mother crystal of an alkaline earth chalcogenide crystal (SrS, CaS, MgS, etc.) is general, and particularly Eu, Sm, and / or Alternatively, a material to which Ce is added at the same time, for example, CaS: Eu, Sm, SrS:
Eu, Sm, SrS: Ce, Sm are often used. Based on FIG. 1, the operation will be described by taking CaS added with Eu and Sm as an example. First, the excitation operation will be described. When the phosphor is irradiated with excitation light (> 480 nm), the electrons of the Eu 2+ ions are excited by the conductor, and Eu 3+ ions are formed. The excited electrons are
It moves through the conductor and is captured by Sm3 + ions, and Sm3 + becomes S
It becomes m2 + ion. This is the excited state (b). Next, the stimulation operation will be described. When the phosphor is irradiated with stimulating light (1 to 1.5 μm), the trapped electrons are released to the conductor again, and the Sm2 + ions become Sm3 +. This electron is captured by Eu3 + ion and Eu2 +
To return to the ground state through the excited state of. At this time, Eu2
Emission of + ions (660 nm) occurs. This is the stimulated state (c), that is, infrared stimulated emission. This principle can be applied to an optical memory. Information is written by irradiating the phosphor with a certain signal (excitation light) replaced with light. Next, the phosphor is irradiated with light having a different wavelength (stimulation light), the information written by the above method is output as stimulated emission, and the information is read using a photoelectric conversion element. To erase the information written in the phosphor,
It is performed by irradiating strong stimulation light. In this way,
The photostimulable phosphor can have an optical memory function. Further, the stimulated phosphor can be applied to an infrared-visible conversion element by the following method. The stimulated phosphor is irradiated with excitation light in advance to preexcite the electrons. That is, electrons are trapped in the level of Sm ions on the entire surface of the stimulated phosphor. When this phosphor is irradiated with infrared light, the electrons captured in the irradiated portion are released to the conductor again, and stimulated emission occurs. By the method described above, a light-light conversion element that converts an image of infrared light into stimulated emission that is visible light can be formed. The infrared-visible conversion element using the above-described stimulated phosphor is Jp
n. J. Appl. Phys. 31 (1992) 715
Jpn. J. Appl. Phys. 32 (1993)
3187 Proposed in Japanese Patent Laid-Open No. 5-51580.

When the photostimulable phosphor is applied to an optical memory or a light-to-light conversion element, it is important that characteristics do not change with time. As described above, the stimulated phosphor is E
Two kinds of rare earth ions, as represented by u and Sm, are added to the phosphor to have a function as an electron generation source and a capture source. Here, when Eu ions and Sm ions are close to each other, interaction occurs between the ions. For example, electrons that are once captured by Sm ions and are in a written state may move to a level formed by Eu ions in the holding process. In an optical memory device, this problem leads to a change in written information over time, and at the present time, a practical memory holding time has not been achieved. It is also reported that the amount of written information will be halved in just a few days. Japanese Patent Laid-Open No. 5-51580 proposes a solution to the above-mentioned problems. Here, by controlling the concentration distribution of Eu ions and Sm ions in the phosphor, the proximity of the two is suppressed. However, as a method for producing the phosphor here, a method of sintering powder is adopted as in the conventional method. The phosphor formed by this method becomes a polycrystalline body having a grain size of several μm to several tens μm depending on the manufacturing conditions.
The part where the ions are present at a high concentration and the part where the Sm ions are present at a high concentration are separated at the grain boundaries. The electrical characteristics between crystals separated by grain boundaries are easily affected by disturbance. For example, when impurities in the atmosphere are adsorbed on the grain boundaries, the electric resistance may decrease, and electrons may move across the grain boundaries.
The above method cannot completely suppress the interaction between Sm and Eu ions. In order to suppress the influence of grain boundaries, it is necessary to single-crystallize the phosphor. When a single crystal material is used, the influence of disturbance can be reduced, and the levels not involved in basic operation can be significantly reduced. However, there is a problem that the position resolution of writing and reading is significantly lowered because the free path of electrons becomes long. The optical memory device requires high density, and the light-to-light conversion device requires high image resolution, so that high position resolution is required. It is difficult to solve the conventional problems by simple crystallization of the material forming the phosphor.

[0004]

[Object] The present invention has been made to solve the problems of conventional photostimulable phosphors, and an object thereof is to provide a photostimulable phosphor having excellent long-term stability.

[0005]

[Structure] FIG. 2 shows the structure and operation of the photostimulable phosphor according to the present invention. The stimulable phosphor of the present invention is characterized in that it has a heterojunction composed of a fluoride material and a sulfide material having a common alkaline earth element. As shown in the figure, the alkaline earth fluoride material has a wide bandgap (~ 10e).
It is an insulating material having V), and a discontinuous band structure can be formed by a heterojunction of a fluoride material and a sulfide material. The electrons excited in the conductor by the exciting light or the stimulating light do not have enough energy to cross the barrier of the fluoride material. Therefore, with the configuration shown in the figure, electrons can be confined in the well layer made of the sulfide material. The alkaline earth fluoride materials include CaF ₂ , SrF ₂ , BaF ₂ ,
Materials such as MgF ₂ can be used. Further, as the alkaline earth sulfide material, materials such as CaS, SrS, BaS and MgS can be used. Rare earth elements added to sulfide include
Elements such as Eu, Sm and Ce can be used. CaF ₂ as a fluoride material and CaS: Eu, Sm as a sulfide material
The operation of the element having this configuration will be described by taking the case of using as an example. As described above, stimulated emission requires a level at which electrons are generated by irradiation with excitation light and a level at which the electrons are retained. The former is formed by adding Eu ions to CaS, and the latter is formed by adding Sm ions to CaS. As shown in the figure, in the present invention, the Eu ion added portion (C
aS: Eu) 21 and Sm ion added portion (CaS: S)
m) 22 separated with CaF ₂ 23 to form. The electrons 25 generated by the irradiation 24 of the excitation light are confined in the well layer. When moving electrons, bias voltage 2 is applied to the phosphor.
6 is applied. By forming the fluoride layer with a film thickness of several hundred liters or less, it is possible to move electrons to an adjacent holding portion by tunneling by applying a bias voltage. Further, the stimulated emission 28 is similarly obtained by irradiating the stimulating light 27 with a bias voltage applied. In the stimulable phosphor having the structure according to the present invention, electrons that have once moved can be retained in the layer unless a bias voltage is applied. In the conventional element, there has been a problem that electrons in a written state captured by Sm ions move to a level formed by Eu ions in the holding process, so that memory characteristics and the like change with time. With this method, the movement of electrons due to uncertain factors can be completely suppressed, and a stimulated phosphor having excellent long-term stability can be formed. In order to control electron transfer by tunneling, a good heterojunction must be formed. When forming a heterojunction between dissimilar materials, it is necessary to consider the difference in lattice constant, the difference in crystal chemical properties, and the forming method. For example, C
In the case of the combination of aF ₂ and CaS, the lattice mismatch ratio is about 4%. Further, both materials are materials having a strong ionic bond property. Further, a heterojunction can be formed by a method in which a forming atmosphere is manipulated after one of the materials is formed and sulfur atoms and fluorine atoms are replaced. In the present invention, a heterojunction between an insulator and a stimulated phosphor is formed by taking advantage of the above advantages. Combination of other materials, SrF ₂ / SrS, Ba
Similar advantages are obtained in the case of F ₂ / BaS and MgF ₂ / MgS.

The stimulable phosphor having the structure shown in FIG. 2 has the granular material shown in FIG. 3, the laminated structure of the thin film shown in FIG. 4, and the sulfide material embedded at an arbitrary position in the fluoride material shown in FIG. It can be realized with a structure. Next, a forming method for each shape will be described. In the case of forming the powder phosphor shown in FIG. 3, sulfide materials having different added rare earth elements are used. After mixing this material, it is heated in a fluorine atmosphere in vacuum. Sulfur, which constitutes a sulfide material, is a material having a high vapor pressure. Therefore, by heating in vacuum, the sulfur atoms on the surface of the sulfide material are desorbed. The active alkaline earth atom from which sulfur is desorbed bonds with the fluorine atom in the atmosphere, and the surface of the sulfide material is covered with the fluoride material as shown in FIG. The sulfide material subjected to the above treatment has a particle size of 100 nm to 100 μm, preferably 1 μm or less, and a rare earth element added in the range of 0.01 to 10 at%, preferably 0.5 to 2 at%. To do. If the particle size of the sulfide material is less than 100 nm, it is difficult to prepare, and if it exceeds 100 μm, the effect of the invention cannot be obtained. Further, the addition amount of the rare earth element is 0.01 at
If it is less than%, the absolute number as an electron generation source or a capture source is too small to achieve device performance. This is because if the content exceeds 10 at%, the crystallinity of the sulfide that is the base material deteriorates. Further, the layer thickness of the fluoride material coating the sulfide material is 10Å to 1 μm, preferably 5000Å or less. This is because if the film thickness of the fluoride material is less than 10Å, the film becomes non-uniform, which causes a change in characteristics over time, and if it exceeds 5000Å, it is difficult to prepare.

A method of forming the thin film structure shown in FIGS. 2 and 4 will be described. The stimulated phosphor can be formed by either a polycrystalline thin film or an epitaxial growth film, but it is preferably formed by an epitaxial growth film. The substrate on which the phosphor is grown epitaxially is
A material such as single crystal Si can be selected. The band diagram of FIG. 2 can be formed by the periodic structure in which the fluoride material and the sulfide material are laminated on the Si substrate. Here, different rare earth elements such as Eu and Sm are added to the sulfide material in the process of growing. As a method for forming the thin film, a metal organic growth method (MOCVD), a sputtering method, a molecular beam epitaxial growth method (MBE), or the like can be used. When each thin film is epitaxially grown, M
The BE method is preferred. The film thickness of the fluoride material is 10Å-5
Set to 00. Further, the sulfide material has a film thickness of 10Å to 50
The concentration of the rare earth element added in the film is set to 0.01 to 10 at%, preferably 0.5 to 2 at%. If the film thickness of the fluoride material is less than 10 Å, the film becomes non-uniform, which causes a change in characteristics over time.
This is because the operation of the device becomes unstable when it exceeds 500Å. Further, if the film thickness of the sulfide material is less than 10 Å, the film becomes non-uniform, which causes a change in characteristics with time.
This is because the operation of the device becomes unstable if it exceeds Å. Furthermore, when the concentration of the rare earth element in the film is less than 0.01 at%, the absolute number as an electron generation source or a capture source is small,
Sufficient device performance cannot be achieved. This is because if it exceeds 10 at%, the crystallinity of the sulfide material as the base material deteriorates.

A method for producing a structure in which the stimulable phosphor shown in FIG. 5 is filled with a sulfide material at an arbitrary position in a fluoride material will be described. It is known that when an alkaline earth fluoride material is irradiated with a high-energy electron beam, only the fluorine atom in the irradiated portion is desorbed. In the present invention, a stimulated phosphor is formed by utilizing the property of this alkaline earth fluoride material. This method forms a sulfur atmosphere and irradiates an arbitrary position of the fluoride thin film with an electron beam, and the alkaline earth atom in the active state by desorption of fluorine and the active sulfur atom reacts with the alkaline earth sulfide. It forms things. That is, according to this method, the alkaline earth sulfide can be formed in any shape in any position in the fluoride thin film.
Here, the sulfur atmosphere is formed by introducing CS ₂ and H ₂ S gas into a vacuum. It is preferable to irradiate the electron beam with an accelerating voltage of 1 to 30 kV. The irradiation area, that is, the area where sulfides are formed, is a circle with a diameter of 500Å to 10 μm, or a width of 50
The stripe shape is 0 Å to 10 μm. The diameter is 50
This is because if it is less than 0 Å, it is difficult to make it, and if it exceeds 10 μm, sufficient device performance cannot be achieved. Further, if the width is less than 500 Å, it is difficult to manufacture, and if it exceeds 10 μm, sufficient device performance cannot be achieved. The stimulated phosphor according to the present invention requires a counter electrode to apply a bias voltage. As the electrode material, a transparent conductive material such as ITO, In ₂ O ₃ , SnO ₂ , ZnO: A
1 and the like can be used, and these materials are MO
It can be formed by a method such as a CVD method, a sputtering method, or a vacuum evaporation method. Further, when the stimulated phosphor is formed by epitaxial growth, single crystal Si that also serves as an electrode and a supporting substrate, or a Si thin film formed on a quartz substrate can be used as an electrode material. Each configuration and its effect will be specifically described by way of examples. Example 1 is an attempt to solve the problems by the conventional method by using the stimulable phosphor having the structure shown in FIG. Example 2 is an application of the photostimulable phosphor having the structure shown in FIG. 4 to an optical memory device. Example 3 is
The stimulated phosphor having the structure shown in FIG. 5 improves the positional resolution, which has been a problem in the conventional infrared-visible light conversion element.

[0009]

【Example】

Example 1 The stimulated phosphor shown in FIG. 3 will be described. Particle size is 10μ
CaS containing about m Eu and C containing Sm
After sufficiently mixing the aS powder, it is inserted into a vacuum firing furnace. Introduce F ₂ gas diluted with Ar gas into the firing furnace,
The powder is heated at a temperature of 00 ° C. In the above atmosphere, C
Sulfur atoms with high vapor pressure are desorbed from the surface of aS3, and active Ca reacts with F ₂ gas in the atmosphere. The surface of the results CaS3 powder is coated with CaF ₂ 31.
By treating in the above atmosphere for about 30 minutes, CaS
A CaF ₂ layer 31 of about 150 Å can be formed on the surface of No. 3. The infrared-visible conversion element according to the present embodiment is completed by dispersing the phosphor formed by this method in an organic binder at a high density, sandwiching the top and bottom of the phosphor with a transparent conductive film 32, and covering with a moisture-proof film 33. As described above, the conventional stimulated phosphor is susceptible to the atmosphere during use because of the existence of grain boundaries. On the other hand, the phosphor according to the present embodiment solves the above problem by the structure in which the surface is coated with CaF ₂ .

Example 2 A method for producing a photostimulable phosphor having a laminated structure of CaS: Eu, Sm and CaF ₂ thin films shown in FIG. 4 will be described.
The stimulated phosphor according to this embodiment is the MBE device 6 shown in FIG.
Are formed by using. First, the device configuration will be described. This device 6 has an ultimate vacuum degree in the ultra-high vacuum region (≦ 10 ⁻⁹
Torr). CaF ₂ and Ca
For S, each solid raw material was supplied by sublimation from Knudsen cells 63 and 65. The Eu and Sm ions were decomposed and purified by plasma immediately after the fluoride of each material was sublimated from the Knudsen cells 62 and 66. CS ₂ and H ₂ S gas can be introduced into a vacuum, and 10 ⁻⁷ Torr to 10T
The sulfur atmosphere 61 can be formed in the range of orr. In addition, an electron gun 64 is attached to this device. This electron gun was used when forming the structure of Example 3, and the accelerating voltage was 1 to 30.
Irradiation to any position on the substrate is possible under the condition of kV.
Next, a method for manufacturing the element shown in FIG. 4 will be described with reference to FIG.
A Si wafer is used as the substrate 44. After inserting the substrate 44 into the MBE apparatus of FIG. 6, a Si clean surface is formed by flash heating at 1200 ° C. After that, the substrate temperature is set to 600.
The CaF ₂ thin film 42 is epitaxially grown to a film thickness of 500 Å at a temperature of ℃. Next, the CaS thin film 41 and the CaF ₂ thin film 43 are epitaxially grown to a film thickness of 500Å and 80Å, respectively. In this embodiment, CaS (500Å) / Ca
A layer structure of F ₂ (80 Å) was formed for 10 cycles. here,
When the CaS thin film was grown, Eu and Sm ions were alternately irradiated to form a CaS: Eu / CaF ₂ / CaS: Sm structure. Next, the CaF ₂ thin film 42 is epitaxially grown to a film thickness of 500 Å. Finally, the ITO thin film 4 is formed to a thickness of 1000 Å by the sputtering method. The photostimulable phosphor of this example shown in FIG. 4 is completed by the above method.
The operation of this element will be described. The above phosphor was irradiated with a semiconductor laser diode of 830 nm and 1 mW as a writing light source. In the irradiation process, a bias voltage of 50 V was applied to the phosphor. After that, the phosphor was left standing with the bias voltage application stopped. The written information was read using a semiconductor laser diode having a wavelength of 1.3 μm and 1 mW and a bias voltage of 50 V applied to the phosphor. As a result, stimulated emission with a central wavelength of 660 nm was observed. As shown in the above results, a phosphor capable of performing an optical memory was realized by the configuration of this example.

Example 3 In this example, a photostimulable phosphor having the structure shown in FIG. 5 will be described. The stimulated phosphor according to this embodiment is formed by the MBE apparatus shown in FIG. 6 as in the second embodiment. The creating method will be described with reference to FIG. A Si wafer is used for the substrate 7. After insertion into the apparatus, a clean surface of the Si substrate is formed by flash heating at 1200 ° C. Then C
An aF ₂ thin film 71 is epitaxially grown to a film thickness of 3000Å. Next, H ₂ S gas 72 and Eu and Sm ions 73 are introduced into the atmosphere to form the atmosphere. In this state, the converged electron beam 74 is applied to the surface of the CaF ₂ thin film by the method shown in the figure. _On the surface of the CaF ₂ thin film 71,
Desorption of the fluorine atom occurs. The Ca atom in the active state where the fluorine atom is desorbed is bonded to the sulfur atom in the atmosphere. As a result, the CaS:
Eu and Sm75 can be formed. In this example, the CaS portion was formed in the CaF ₂ thin film with a 1 μm pitch and a 1 μm diameter shape by operating the electron gun. The electron beam acceleration voltage was adjusted so that the depth of the CaS portion was 1000 to 1500 Å. Then, in the same manner as above, CaF ₂
Epitaxially grow a thin film with a thickness of 2000Å
The S portion was embedded in the thin film. By repeating this method, the layer structure shown in FIG. 7D can be formed. The ITO thin film 77 which is a transparent electrode is added to the phosphor having the above structure.
Then, an AC voltage was applied and the emission form of EL emission was examined. As a result, dot-like EL emission with a diameter of 1 μm was observed, and CaS ₂ was formed in the CaF ₂ thin film by this growth method.
It was confirmed that the parts could be formed in controlled positions and shapes. When the stimulated phosphor is applied to a light-to-light conversion element, position resolution is an index for evaluating its performance.
The resolution of the stimulated phosphor according to this example was evaluated. The phosphor having the above structure was irradiated with a semiconductor laser of 1.545 μm and 10 mW. Here, the irradiation diameter of the laser light was 10 μm. As a result of observing the state of stimulated emission,
Red stimulated luminescence could be observed in dots within a diameter of 10 μm.
Usually, the position resolution is evaluated by LSF (line spre).
It is performed with a full width at half maximum of (ad function). The half-width value of the LSF of the conventional element is about 100 to several hundreds μm, and good resolution has not been obtained. This is because the electrons excited by the conductor during reading and writing are diffused. On the other hand, from the above results, there is a possibility that the element according to the present embodiment can obtain a resolution of about 1/10. This is because the structure in which CaS functioning as a phosphor is embedded in the CaF ₂ thin film was realized. The movement of excited electrons is restricted within the CaS dot.
Therefore, in this configuration, the position resolution can be determined by the shape of CaS, and a resolution that cannot be realized by a normal phosphor is possible.

Specific embodiments of the present invention will be described below. 1. In a stimulated phosphor material containing an alkaline earth chalcogenide crystal containing at least one kind of rare earth element, the surface of the phosphor material is a stimulated fluorescent material characterized by being coated with an alkaline earth fluorine compound. Body material. 2. The above-mentioned first stimulated phosphor material, wherein the alkaline earth chalcogenide crystal and the alkaline earth of an alkaline earth fluorine compound are common. 3. In the first or second photostimulable phosphor material, the photostimulable phosphor material, wherein the phosphor material has a granular shape. 4. The third stimulable phosphor material, wherein the particle size of the granular material is 100 nm to 100 μm, preferably 1 μm or less. 5. The said 1st, 2nd, or 3rd stimulated phosphor material WHEREIN: The layer thickness of a fluoride material is 10Å-1 micrometer, Preferably it is 5000Å or less. 6. A stimulable phosphor material having a structure in which an alkaline earth chalcogenide thin film containing at least one kind of rare earth element and an alkaline earth fluorine compound thin film are sequentially laminated. 7. In the sixth stimulated phosphor material, the film thickness of the fluoride material is 10Å to 500Å, and the film thickness of the sulfide material is 10Å to 5000Å. 8. The stimulated phosphor material of 6 or 7, wherein the alkaline earth chalcogenide crystal and the alkaline earth of the alkaline earth fluorine compound are common. 9. In the stimulated phosphor material of 6, 7 or 8 above,
A stimulable phosphor material having a rare earth element concentration of 0.01 to 10 at%, preferably 0.5 to 2 at%. 10. A stimulable phosphor material comprising an alkaline earth fluorine compound thin film having a structure in which an alkaline earth chalcogenide portion containing at least one kind of rare earth element is present in the thin film. 11. The tenth stimulated phosphor material, wherein the alkaline earth chalcogenide portion is a circle having a diameter of 500Å to 10 μm, or a stripe shape having a width of 500Å to 10 μm. 12. The said 10th or 11th stimulated phosphor material WHEREIN: The stimulated phosphor material whose alkaline earth chalcogenide crystal and alkaline earth of an alkaline earth fluorine compound are common. 13. The first, second, third, fourth, fifth, sixth, seventh, eighth, ninth,
In the stimulated phosphor material of 10, 11 or 12, the combination of the alkaline earth chalcogenide and the alkaline earth fluorine compound is CaF ₂ / CaS, SrF ₂ / SrS, BaF.
_A stimulable phosphor material which is at least one selected from the group consisting of ₂ / BaS and MgF ₂ / MgS. 14. Conductive thin film, the first, second, third, fourth, fifth, sixth,
On the substrate, a stimulable phosphor thin film and a transparent conductive thin film made of at least one stimulable phosphor material selected from the group consisting of 7, 8, 9, 10, 11, 12, and 13 stimulable phosphor materials. An infrared-visible conversion element, characterized in that a mechanism for applying a DC or AC voltage to the photostimulable phosphor is provided by sequentially laminating the layers.

[0013]

[Effect] By forming a stimulable phosphor with two kinds of materials, that is, an alkaline earth chalcogenide crystal and an alkaline earth fluorine compound material, for example, in the configuration according to the first embodiment, the influence of the use environment on the phosphor can be reduced. You can Also,
When the phosphor having the configuration shown in Example 2 is applied to an optical memory device, it is possible to reduce the change with time in the writing state, which has been a problem in conventional devices. This is because the movement of electrons can be restricted by the alkaline earth fluorine compound material.
Further, by devising the manufacturing method, the photostimulable phosphor having the structure of Example 3 can be obtained. With the stimulable phosphor of this structure,
When the light conversion element is formed, it becomes possible to realize high resolution which cannot be realized by the conventional element.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a light emission principle of a stimulated phosphor containing Eu2 + ions and Sm3 + ions. It is a figure which shows the band model of (a) stimulated fluorescent substance. (B) It is a figure explaining the excited state at the time of irradiating a fluorescent substance with excitation light. (C) It is a figure explaining the state returned to the ground state by irradiating the phosphor in the excited state of (b) with stimulating light.

FIG. 2 is a diagram illustrating the configuration and operation of the photostimulable phosphor of the present invention. (A) It is a figure which shows the structure before excitation. (B) It is a figure which shows the structure of an excitation operation and an excitation state. (C) It is a figure which shows the structure of a bias voltage application operation and an application state. (D) It is a figure which shows the structure of a stimulated light emission, stimulated light emission operation, and a light emission state.

FIG. 3 is a diagram schematically showing the structure of a stimulable phosphor of the present invention composed of a granular material.

FIG. 4 is a diagram schematically showing the constitution of the photostimulable phosphor of the present invention composed of a laminate of thin films.

FIG. 5 is a diagram schematically showing a configuration of a stimulable phosphor of the present invention configured by embedding a sulfide material at an arbitrary position in a fluoride material.

FIG. 6 is a diagram illustrating a configuration of an MBE device used in Examples 2 and 3 and a production operation of a stimulated phosphor.

FIG. 7 is a diagram illustrating a method for producing a stimulated phosphor of Example 3. (A) It is a figure which shows the board | substrate which consists of Si wafers. (B) is a diagram showing the substrate of CaF ₂ thin film epitaxially formed (a). (C) It is a figure which shows selective CaS: Eu, Sm part formation operation and the structure of the photostimulable phosphor after forming the said part. (D) CaF ₂ in which CaS is formed in a dot shape in the layer
It is a figure which shows a thin film.

[Explanation of symbols]

21 CaS layer added with Eu ions 22 CaS layer added with Sm ions 23 CaF ₂ layer 24 Irradiation of excitation light 25 Electrons 26 Bias voltage 27 Stimulation light 28 Stimulated emission 3 CaS particles containing Eu or Sm 31 CaF ₂ layer 32 transparent conductive film 33 moisture-proof film 4 transparent conductive thin film 41 CaS thin film (alternatively containing Eu ions or Sm ions) 42 CaF ₂ thin film 43 CaF ₂ thin film 44 substrate 5 transparent conductive thin film 51 sulfide 52 fluoride thin film 53 substrate 6 MBE Apparatus 61 Sulfur atmosphere formed by CS ₂ or H ₂ S gas 62 Sm ion source 63 CaF ₂ source 64 electron gun 65 CaS source 66 Eu ion source 67 substrate 7 substrate 71 CaF ₂ thin film 72 H ₂ S gas 73 Eu and Sm ions 74 Electron beam 75 CaS: E , CaF ₂ that Sm portion 76 CaS is formed in dots in the layer
Thin film 77 ITO thin film

Claims (5)

[Claims] 1. A stimulable phosphor material composed of an alkaline earth chalcogenide crystal containing at least one kind of rare earth element, wherein the surface of the alkaline earth chalcogenide crystal is coated with an alkaline earth fluorine compound. A stimulable phosphor material characterized by the above. 2. A stimulable phosphor material having a structure in which an alkaline earth chalcogenide thin film containing at least one or more kinds of rare earth elements and an alkaline earth fluorine compound thin film are sequentially laminated. 3. A stimulable phosphor material comprising an alkaline earth fluorine compound thin film having a structure in which an alkaline earth chalcogenide portion containing at least one or more kinds of rare earth elements is present in the thin film. 4. An electroconductive thin film, the photostimulable phosphor thin film according to claim 2, and a translucent electroconductive thin film are sequentially laminated on a substrate, and a mechanism for applying a DC or AC voltage to the photostimulable phosphor is provided. An infrared-visible conversion element characterized by. 5. A conductive thin film, the photostimulable phosphor thin film according to claim 3, and a translucent conductive thin film are sequentially laminated on a substrate, and a mechanism for applying a DC or AC voltage to the photostimulable phosphor is provided. An infrared-visible conversion element characterized by.