Miyuki Miyamoto

Scintillation Properties of In Doped ZnO With Different In Concentrations

Using the liquid phase epitaxy (LPE) method we prepared the high crystalline quality In3+ doped ZnO thin film scintillators with different Indium concentration of 26, 53, and 141 ppm. We evaluated their optical properties and radiation response, because there are few reports of radiation response of In-doped ZnO scintillator. In order to imitate the scintillator application, we measured the alpha-ray excited luminescence spectra. The emission bands peaking around 375 and 500 nm were observed, and with an increment of In3+, the intensity of both bands decreases. In the measurement of light yield, we optically coupled the sample with PMT R7600 by a silicone grease, and excitation was provided by 241Am 5.5 MeV-rays. The samples showed of about 10% of the light yield of BGO scintillator which was used as a reference. Under the same excitation the scintillation decay was measured in all the samples as well.

Growth of Thick Zinc Magnesium Oxide by Liquid Phase Epitaxy

Very thick (about 0.5 mm) single crystals of a (Zn,Mg)O were grown on ZnO substrate by using a liquid phase epitaxy (LPE) technique. The source materials, ZnO and MgO, were dissolved in a PbO–Bi2O3 flux, and the (Zn,Mg)O was crystallized on the c-face of ZnO substrate in contact with the melt. The obtained crystal had high crystallinity similar to that of the ZnO substrate and exhibited n-type conductivity with relatively high Hall mobility.

Optical and scintillation properties of Cd-doped ZnO film

In the present study, we developed high crystalline quality Cd2+-doped ZnO (Cd:ZnO) scintillator by the liquid phase epitaxy (LPE) method to enhance the defect related emission in ZnO for α-ray detectors. In order to imitate the scintillator application, we investigated α-ray induced radio luminescence spectrum and emission bands peaking around 380 and 500 nm were observed, and the latter one was largely enhanced when compared with pure ZnO. Then, we optically coupled the sample with PMT R7600 by Silicone grease, and irradiated 241Am 5.5 MeV α-ray. Cd:ZnO showed about 700% light yield of pure ZnO scintillator and the total light yield turned out to be 18000 photons/5.5 MeV-α. The main component of the scintillation decay time constants turned out to be ~1 ns and 2 µs due to the free exciton and the defect related emissions, respectively.

Development of ZnO Based Charged Particle Monitor for Processing Facility

In the present paper, we describe the development of an α-ray imaging detector based on a ZnO single crystalline scintillator and a position-sensitive photomultiplier tube (PSPMT). The ZnO crystal was grown by the hydrothermal synthesis method with 2-in.- in diameter. The ZnO specimen was polished out to be 0.5 mm in thickness. After optically coupling with PSPMT, the crystal was irradiated with 241Am α-ray for evaluation of both spatial resolution and pulse height spectrum. Using the charge center of the gravity method, two-dimensional α-ray images were successfully obtained. The efficiency of the energy window in terms of imaging quality was also examined.

Evaluations of ZnO based α-ray imager

In the present paper, we describe the development of an α-ray imaging detector based on a ZnO single crystalline scintillator and a position-sensitive photomultiplier tube (PSPMT). The ZnO crystal was grown by the hydrothermal synthesis method with 2-inch-φ in diameter. The ZnO specimen was polished out to be 0.5 mm in thickness. After optically coupling with PSPMT, the crystal was irradiated with 241Am α-ray for evaluation of both spatial resolution and pulse height spectrum. Using the charge center of the gravity method, two-dimensional α-ray images were successfully obtained. The efficiency of the energy window in terms of imaging quality was also examined.

Thermal Analysis of Liquid Phase Epitaxy of ZnO and Characteristics of Some Li-Doped Mg0.06Zn0.94O ∕ ZnO Heterostructure

Thermogravimetry and differential thermal analysis (TG/DTA) were used to examine a process capable of fabricating homoepitaxial, single-crystalline Me x Zn 1-x O (Me = Mg, Ga, etc.) films under thermodynamically stable conditions by liquid phase epitaxy. A liquid solution of alkaline metal (Li, Na, Cs) chlorides is employed at temperatures of 580-650°C. A reaction of Me +n -Cl n /ZnCl 2 with polycrystalline K 2 CO 3 is applied to continuously form Me x Zn 1-x O over a ≥ 16 h process cycle under ambient air atmosphere and pressure as shown by TG/DTA. Mirrorlike films with a thickness ≤ 3 μm have been grown. The high structural quality of the film with sharp interfacial transition from substrate to film has made it possible to observe a surface conductive channel. Temperature-dependent Hall measurement on Li-doped Mg 0.6 Zn 0.94 O/ZnO heterostructures under vacuum conditions discloses a high-resistivity state with 10 3 Ω cm at 300 K and a low-resistivity state with < 10 Ω cm at 550 K.

LPE Growth and Scintillation Properties of (Zn,Mg)O Single Crystalline Film

Among the direct wide band-gap semiconductors, ZnO is an attractive scintillator for alpha particle monitoring. However, the undoped ZnO has a dominant slow luminescence around 500-600 nm due to lattice defects. In this study, the Mg-substituted ZnO ((Zn,Mg)O) single crystalline films with high crystallinity are investigated. Mg doping is found to improve the lattice order and suppress slow luminescent component around 500-600 nm. (Zn,Mg)O single crystalline films were grown by the Liquid Phase Epitaxy (LPE) method. Alpha-ray excited radioluminescence spectra of (Zn,Mg)O film show only one emission peak around 400 nm and decay time of a few nanoseconds. This emission is assigned to free exciton. Light yield of LPE grown (Zn,Mg)O film is evaluated of about 90% of BGO.

Comparative study of Ga, In, and Mg doped ZnO thin-film scintillator with Geiger mode APD

Ga 25, 55, and 552 ppm doped, In 25, 53, and 141 ppm doped, Mg 1, 5, 10, 13 mol% doped ZnO thin film scintillators were grown by the Liquid Phase Epitaxy (LPE) method. Their transmittance, α-ray induced emission spectra were evaluated. The transmittance reached to 80% at wavelength longer than 390 nm for all the crystals. Two emission lines appeared at 390 and 550 nm, due to the free and bound excitons, respectively. Coupled with Multi Pixel Photon Counter (MPPC), the light yield and decay time were evaluated.