X-Ray Luminescence of ZnO Whisker Microstructures
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Luminescence of ZnO Whisker Microstructures A. E. Muslimova*, I. D. Venevtseva, L. A. Zadorozhnayaa, P. A. Rodnyib, and V. M. Kanevskya a
Crystallography and Photonics, Federal Scientific Research Center, Russian Academy of Sciences, Moscow 119333 Russia b Peter the Great St. Petersburg Polytechnic University, St. Petersburg, 195251 Russia *e-mail: [email protected] Received December 19, 2019; revised March 16, 2020; accepted April 20, 2020
Abstract—Morphology and the optical and luminescent properties of zinc oxide (ZnO) whisker microcrystal arrays grown on sapphire using gas-transport synthesis from zinc vapors in oxygen by vapor–liquid–solid (VLS) mechanism have been studied. The arrays consisted of uniaxial microcrystals with two morphologies, combining hexagonal prisms and single-crystalline microrods. Short-wavelength boundary of transparency of the whisker microcrystal arrays occurs in a region of 385−395 nm. Total transmission in the visible and near-IR spectral range is on a level of 10–20% for layer thicknesses about 15–18 μm. The X-ray luminescence spectrum displays two bands: (i) an intense narrow excitonic peak at 388.3 nm and (ii) an about 2.5 times less intense broad band in a region of 430−600 nm. The time constant of the decay of excitonic luminescence from undoped ZnO microstructures has been estimated for the first time at about 1.1 ns (with the exciting pulse width not taken into account). Keywords: ZnO, microstructures, X-ray luminescence. DOI: 10.1134/S1063785020070214
The development and launch of modern highenergy high-luminosity accelerators requires creating detectors with improved spatiotemporal and energy resolution characteristics. No less important requirements are posed as concerns the reliability of operation, radiation resistance, and simplicity and cost of manufacturing technology. All these requirements can be satisfied by scintillation counters, although the task of manufacturing scintillators combining relatively high light yield and short response time is still not solved. At present, the most promising material for use as a scintillator is believed to be zinc oxide (ZnO) but a temporal resolution satisfactory for applications has been only achieved with the use of bulk ZnO crystals [1]. This is related to the fact that the emission spectrum of ZnO usually contains two components: excitonic luminescence near the fundamental absorption edge (380−400 nm wavelength) and green luminescence with maximum intensity in the region of 450−650 nm [2]. The excitonic luminescence of ZnO has a characteristic time below 1 ns [3], which allows it to be used in scintillation counters. In contrast, the green luminescence produced by defects of the ZnO crystal lattice [2, 4] has a characteristic time on the order of 1 μs, albeit at a much higher light yield. Bulk ZnO crystals possessing a perfect crystalline structure exhibit predominantly excitonic luminescence and are successfully used for detecting γ and X-ray photons,
which requires a rather large volume of material. However, existing techn
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