Optical Properties of Thick Zinc Oxide Films Doped with Gallium and Gold
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ACE AND THIN FILMS
Optical Properties of Thick Zinc Oxide Films Doped with Gallium and Gold A. E. Muslimova,*, V. M. Kanevskya, I. D. Venevtsevb, and A. M. Ismailovc a Shubnikov
Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” Russian Academy of Sciences, Moscow, 119333 Russia b Peter the Great St. Petersburg Polytechnic University, St. Petersburg, 195251 Russia c Dagestan State University, Makhachkala, 367008 Russia *e-mail: [email protected] Received January 23, 2020; revised March 24, 2020; accepted March 25, 2020
Abstract—Samples of thick (30–32 μm) films of pure and gallium- and gold-doped zinc oxide obtained by magnetron sputtering using an uncooled target have been investigated. It is shown that the main changes in the optical properties of undoped thick ZnO films during recrystallization annealing under atmospheric conditions occur for the first 2–3 h. It is found that doping of thick ZnO films with gallium (4 at %) without additional heat treatment doubles the transmittance (to a value of about 97%). At the same time, this introduced gallium concentration leads to concentration quenching of X-ray luminescence. The results of measuring temporal characteristics show that the shapes of X-ray luminescence kinetics of samples with a gold buffer layer after heat treatment and undoped ZnO samples are identical and characterized by a long shoulder of slow luminescence with a characteristic time of about a microsecond and low integrated intensity with a short decay time. DOI: 10.1134/S1063774520050144
INTRODUCTION One of the most promising materials for the main element of scintillation counters, which are appropriate for modern accelerators, is ZnO [1, 2]. This material is characterized by the presence of the exciton (380–400 nm, characteristic fluorescence lifetime less than 1 ns [3]) and green luminescence components. The green component has a maximum in the range of 450–650 nm and a characteristic fluorescence lifetime on the order of 1 μs [4]; it is traditionally related to ZnO lattice defects. Much interest has recently been shown in film technologies and ceramics because of the absence of commercially available technology of preparing ZnO single crystals [5, 6]. However, a large amount of material is required to detect gamma quanta and X rays. It was shown in [7, 8] that ZnO ceramics and thick (>10 μm) films are promising materials for detector elements. Advantages of thick ZnO films include the technological possibility of their direct deposition on a photodetector and high transparency to intrinsic emission, which makes it possible not to limit the detector size. In [8], structural and luminescence properties of undoped thick ZnO films were investigated, and some drawbacks caused by the extremely high (~16 nm/s) film deposition rate were found. The films had a low X-ray luminescence intensity and a low transmittance in the range of 400–
600 nm due to the poor crystal quality (deviation from stoichiometry and presence of impurities, which could be introduc
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