Scintillator laminate and method for manufacturing the same

Abstract

The present invention provides a scintillator laminate capable of forming a single-phase film of yttrium aluminum composite oxide on an inexpensive and transparent substrate, and a method for manufacturing the same. [Solution] Using a laser CVD method, a single-phase yttrium aluminum perovskite (YAP) film 10 is formed on a sapphire substrate 10 with the r-plane as the main surface 11, by supplying the raw materials, yttrium source and aluminum source, in an atomic ratio of Y:Al = 53.5:46.5 to 59.5:40.5, and setting the film deposition temperature to 800 to 1020K, thereby manufacturing a scintillator laminate 1. Cerium or praseodymium can be added to the YAP single-phase film 20.

Description

Technical Field

[0001] The present invention relates to a laminate for a scintillator using yttrium aluminum perovskite as a single crystal of a scintillator and a method for producing the same.

Background Art

[0002] As crystal structures of yttrium aluminum composite oxides, typical ones are garnet structure, perovskite structure, and monoclinic structure. In the case of the garnet structure, it is represented by the composition formula of Y3Al5O where the molar ratio of yttrium oxide (Y2O3) to aluminum oxide (Al2O3) is 3 to 5, and it is called yttrium aluminum garnet (YAG). In the case of the perovskite structure, it is represented by the composition formula of YAlO3 where the molar ratio of Y2O3 to Al2O3 is 1 to 1, and it is called yttrium aluminum perovskite (YAP). The monoclinic structure is represented by the composition formula of Y4Al2O9 where the molar ratio of Y2O3 to Al2O3 is 4 to 2, and it is called yttrium aluminum monoclinic (YAM). 12 The metal composite oxides having garnet structure or perovskite structure are known to be usable as single crystals of scintillators that absorb radiation such as X-rays and emit fluorescence (for example, Patent Document 1 and Patent Document 2). Scintillators are used, for example, in radiation detectors and the like. Patent Document 1 and Patent Document 2 describe forming a scintillator layer made of a metal composite oxide having a garnet structure or a perovskite structure directly on one surface of a base material of a phosphor incorporated as a component in a radiation detector or the like using the laser CVD method.

[0003] In the examples of Patent Document 1 and Patent Document 2, YAG, Al2O3, and strontium titanate (STO, composition formula: SrTiO3) are used as base materials, and a lutetium aluminum composite oxide (LuAG, composition formula: Lu3Al5O

[0004] having a garnet structure is formed on one surface thereof using the laser CVD method. 12It has been described that a scintillator layer made of ) or lutetium aluminum composite oxide (LuAP, compositional formula: LuAlO3) having a perovskite structure was actually formed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-164058 [Patent Document 2] International Publication No. 2023 / 017845 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Yttrium aluminum composite oxides can be formed as single-phase materials with YAG, YAP, or YAM crystal structures, depending on the manufacturing conditions. Alternatively, two-phase materials with YAG and YAP, or two-phase materials with YAP and YAM, may also be formed. For use as a scintillator in radiation detectors, a single-phase garnet or perovskite structure is required. While Patent Documents 1 and 2 suggest YAG and YAP as metal composite oxides usable as scintillator layers, only LuAG and LuAP were actually deposited by laser CVD, and there is no description of the growth conditions for single-phase YAG or YAP films using laser CVD. Furthermore, since the substrate on which the scintillator layer is formed will be directly incorporated into radiation detectors, a transparent and inexpensive material is preferable. However, STO is expensive and has somewhat inferior transparency.

[0007] Therefore, in view of the above circumstances, the present invention aims to provide a scintillator laminate and a method for manufacturing the same that can form a single-phase film of yttrium aluminum composite oxide on an inexpensive and transparent substrate. [Means for solving the problem]

[0008] To achieve the above objective, the present invention, in one aspect, provides a method for manufacturing a scintillator laminate in which a yttrium aluminum perovskite single-phase film is formed on the main surface of a sapphire substrate having an r-plane as the main surface by laser CVD, wherein the supply ratio of the raw materials, yttrium source and aluminum source, is Y:Al = 53.5:46.5 to 59.5:40.5 in atomic ratio, and the film formation temperature is 800 to 1020 K.

[0009] It is preferable to add cerium or praseodymium to form the yttrium aluminum perovskite single-phase film.

[0010] In yet another aspect, the present invention provides a scintillator laminate comprising a sapphire substrate having an r-plane as its main surface, and a yttrium aluminum perovskite single-phase film formed on the main surface.

[0011] It is preferable that the yttrium aluminum perovskite single-phase film is doped with cerium or praseodymium. [Effects of the Invention]

[0012] Thus, according to the present invention, by using a laser CVD method, the supply ratio of the raw materials, yttrium source and aluminum source, is set to an atomic ratio of Y:Al = 53.5:46.5~59.5:40.5, and the film deposition temperature is set to 800~1020K, thereby forming a single-phase yttrium aluminum perovskite (YAP) film on a sapphire substrate, which is an inexpensive and transparent substrate with the r-plane as the main surface. Although sapphire and YAP have different crystal systems, sapphire has high transmittance in the ultraviolet and visible light regions, and its absorption edge is at a wavelength of 200 nm. Therefore, by synthesizing a single-phase YAP film on sapphire, it becomes possible to sufficiently transmit fluorescence emission to the photodetector side when used in radiation detectors and the like. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing one embodiment of the scintillator laminate according to the present invention. [Figure 2] XRD pattern showing the YAP single-phase film of Example 1. [Figure 3] XRD pattern showing the YAP single-phase film doped with Ce of Example 5. [Figure 4] 3DPL spectrum of the YAP single-phase film doped with Ce of Example 5.

Mode for Carrying Out the Invention

[0014] Hereinafter, an embodiment of a laminate for a scintillator and a method for manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

[0015] As shown in FIG. 1, in the method for manufacturing the laminate 1 for a scintillator according to the present embodiment, a yttrium aluminum perovskite (YAP) single-phase film 20 is formed on the main surface 11 of a sapphire substrate 10 having an r-plane as the main surface 11 by a laser chemical vapor deposition (CVD) method.

[0016] As the substrate on which the YAP single-phase film 20 is formed, a sapphire substrate 10 which is relatively inexpensive and has excellent transparency is used. Although there are sapphire substrates having an a-plane, a c-plane, an m-plane, etc. as the main surface, in the present embodiment, a sapphire substrate 10 having an r-plane as the main surface 1 is used. The thickness of the sapphire substrate 10 is preferably, for example, 200 μm or more and 600 μm or less in order to suppress the scattering of fluorescence emission in the YAP single-phase film and to physically hold the YAP single-phase film.

[0017] For film formation by the laser CVD method, a commercially available laser CVD apparatus can be used, and the details are described in Patent Document 1. As a raw material supplied to the laser CVD apparatus, a raw material gas is usually used. As a yttrium source, for example, an organic yttrium compound such as yttrium tris(dipivaloylmethanato) (Y(dpm)3) can be used, and as an aluminum source, for example, an organic aluminum compound such as aluminum tris(acetylacetonato) (Al(acac)3) can be used.

[0018] When the total of the yttrium source and the aluminum source in the raw material gas is taken as 100, the supply ratio of them in atomic ratio should be in the range of Y:Al = 53.5:46.5 to 59.5:40.5. Also, the film formation temperature should be in the range of 800 - 1020K. By setting the supply ratio of Y and Al within this range and the film formation temperature within this range, a YAP single-phase film 20 can be formed on the main surface 11 of the r-plane of the sapphire substrate 10. Note that the atomic ratio of Y and Al in the raw material gas is the ratio when the total of these two is taken as 100. Also, the film formation temperature is the temperature at which the sapphire substrate 10 is irradiated with laser light (not shown) to heat the sapphire substrate 10. By supplying the raw material gas with a carrier gas to the heated sapphire substrate 10, the YAP single-phase film 20 is formed. The atomic ratio of Y and Al in the raw material gas is preferably in the range of 53.7:46.3 to 59.0:41.0, and more preferably in the range of 53.9:46.1 to 58.7:41.3.

[0019] The thickness of the YAP single-phase film 20 is not particularly limited as long as it is suitable for absorbing α-rays and X-rays and transmitting high-energy radiation such as γ-rays. For example, it is preferably 5μm or more and 30μm or less. By adjusting the time for supplying the raw material gas, that is, the film formation time, the thickness of the formed YAP single-phase film 20 can be adjusted.

[0020] In this way, a scintillator laminate 1 can be obtained, which includes a sapphire substrate 10 having an r-plane as the main surface 11 and a YAP single-phase film 20 formed on this main surface 11. Also, transition metal elements such as cerium (Ce) or praseodymium (Pr) can be added to the YAP single-phase film 20 as activating elements. The activating element is preferably added in a ratio of 1 - 10 parts per 100 parts in total of Y and Al in the YAP single-phase film 20 in atomic ratio. By adding such an activating element, for example, when Ce is added, it can exhibit fluorescence emission of the 5d - 4f transition derived from Ce. 3+ It can show fluorescence emission of the 5d - 4f transition derived from Ce.

[0021] In this embodiment, the scintillator laminate 1 has a transparent sapphire substrate 10 and a YAP single-phase film 20 that can be formed with a suitable thickness for use as a scintillator. Therefore, it can be directly incorporated into a radiation detector or the like without transferring it to another substrate or processing it by removing the film thickness. [Examples]

[0022] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0023] [Example 1] A test was conducted to form a yttrium-aluminum composite oxide film on a substrate using the laser CVD apparatus described in Patent Document 1. As the raw material gases, yttrium trisdipivaloyl methanate (Y(dpm)3) was used as the yttrium source, and aluminum trisacetylacetonate (Al(acac)3) was used as the aluminum source. The raw material gases were supplied in an atomic ratio of Y:Al = 58.7:41.3. Argon (Ar) gas was used as the carrier gas. A sapphire substrate with the r-plane as the main surface was used as the substrate. Other film formation conditions are shown below. Laser power density: 79 W / cm² 2 Ar gas flow rate: 100 sccm Oxygen gas flow rate: 100 sccm Raw material vaporization temperature: 190~270℃ Film forming temperature: 947K Deposition pressure: 200 Pa Deposition speed: 85.4μm / h

[0024] The yttrium aluminum composite oxide film formed on the main surface of the sapphire substrate was observed using a scanning electron microscope (SEM), and its crystal structure was analyzed using an X-ray diffraction (XRD) apparatus. The film thickness was 14.2 μm. The appearance was white and opaque, with a faceted surface and a columnar microstructure in cross-section. The obtained XRD pattern is shown in Figure 2. As shown in Figure 2, the peaks were oriented along the (110), (002), (112), (200), and (022), (202) planes, and matched well with YAP. No YAG peaks were observed, confirming the formation of a single-phase YAP film.

[0025] [Examples 2-4, Comparative Examples 1-9] Except for changing the supply ratio of Y and Al in the raw material gas and the film deposition temperature to the conditions shown in Table 1, a yttrium aluminum composite oxide film was formed on a sapphire substrate using a laser CVD apparatus in the same manner as in Example 1, and then observed and analyzed.

[0026] [Table 1]

[0027] As a result, in Examples 2-4, where the supply ratio of Y to Al in the raw material gas was Y:Al = approximately 55:45-59:41 and the film deposition temperature was approximately 810-1020K, it was confirmed that a single-phase YAP film was formed. On the other hand, in Comparative Examples 1-3, where the supply ratio of Y in the raw material gas was less than 53.5 at%, the obtained XRD patterns showed a YAG peak in addition to YAP, and a single-phase YAP film could not be obtained. Similarly, in Comparative Examples 4-6, where the supply ratio of Y in the raw material gas was approximately 55-58 at%, but the film deposition temperature was approximately 1030K or higher, the obtained XRD patterns also showed a YAG peak in addition to YAP, and a single-phase YAP film could not be obtained. In Comparative Examples 7-9, where the supply ratio of Y in the raw material gas was 60 at% or higher, the obtained XRD patterns showed a YAG peak in addition to YAP, and a single-phase YAP film could not be obtained. In particular, in Comparative Example 8, which had the highest film deposition temperature at 1021K, the obtained XRD pattern also showed a YAM peak.

[0028] [Example 5] To form a Ce-doped YAP single-phase film, the supply ratio of Y, Al, and Ce in the source gas was set to Y:Al:Ce = 53.1:45.4:1.5, and cerium tetradipivaloylmethanat (Ce(dpm)4) was used as the cerium source (the atomic ratio of Y and Al in the source gas is 53.9:46.1 when the sum of these two is taken as 100). Except for these differences, a yttrium aluminum composite oxide film was formed on a sapphire substrate using a laser CVD apparatus in the same manner as in Example 1, and then observed and analyzed. The appearance was white and translucent. As shown in Figure 3, the obtained XRD pattern did not show a YAG peak, confirming that a YAP single-phase film had been formed.

[0029] Next, the Ce-doped YAP single-phase film was irradiated with ultraviolet-visible light at wavelengths from 200 nm to 600 nm, and the emission spectrum of the light emitted from the film was measured. The resulting 3D photoluminescence (PL) spectrum graph is shown in Figure 4. The lightness of the color in Figure 4 indicates the emission intensity. As shown in Figure 4, fluorescence emission was measured in the excitation wavelength range of approximately 270 to 320 nm and the emission wavelength range of approximately 320 to 410 nm. 3+ It was confirmed that fluorescence emission originated from the 5d-4f transition. [Explanation of Symbols]

[0030] 1. Laminate for scintillators 10 Sapphire substrate 11. Main surface (r-surface) 20 YAP single phase membrane

Claims

1. A method for manufacturing a scintillator laminate, comprising forming a single-phase yttrium aluminum perovskite film on the main surface of a sapphire substrate having an r-plane as the main surface by laser CVD, wherein the supply ratio of the raw materials, yttrium source and aluminum source, is set to an atomic ratio of Y:Al = 53.5:46.5 to 59.5:40.5, and the film formation temperature is 800 to 1020 K.

2. A method for producing a scintillator laminate according to claim 1, wherein cerium or praseodymium is added to form the yttrium aluminum perovskite single-phase film.

3. A scintillator laminate comprising a sapphire substrate with an r-plane as its main surface and a single-phase yttrium aluminum perovskite film formed on the main surface.

4. The scintillator laminate according to claim 3, wherein cerium or praseodymium is added to the yttrium aluminum perovskite single-phase film.

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