Journal of Luminescence 260 (2023) 119886 Available online 28 April 2023 0022-2313/© 2023 Published by Elsevier B.V. Full Length Article Thermoluminescence properties of TiO 2 /Cu/TiO 2 multilayer thin flms fabricated by (RF/DC) sputtering for radiation dosimetry Ali Saleh Alkadem Idriss a, c, ** , Nik Noor Ashikin Nik Ab Razak a, * , Naser M. Ahmed a, b , Youssef Aboubaker Abdulla c a School of Physics, Universiti Sains Malaysia, 11800, Pulau Pinang, Malaysia b Department of Physics, Faculty of Science, Sebha University, P.O BOX: 18758, 5th of October Street, Sebha, Libya c Higher Institute of Science and Technology Tamzawa-Al Shati, Ministry for Technical and Vocational Education, Tripoli, Libya A R T I C L E INFO Keywords: Dosimetry Multilayer Thermoluminescence (TL) TiO 2 Glow curve Thin flm RF sputtering X-ray radiation ABSTRACT The most popular TLDs are composed of phosphors, ceramics, and crystals. Despite having a high light output per unit of absorbed dose, they suffer from rapid signal fading, light scattering, saturation at higher doses, and diffculties annealing for re-use. Here, we report the characteristics of a novel TiO 2 /Cu/TiO 2 multilayer thin flm dosimeter fabricated using radio-frequency (RF) and direct current (DC) sputtering methods with a faster deposition rate, high purity, and uniformity. The multilayer sequence was set to TiO 2 (150 nm)/Cu (x)/TiO 2 (50 nm), at varying Cu thicknesses (x = 5, 10, 25, 40, and 50 nm). The structure, morphology, elemental compo- sition, and optical properties of the flms were characterized by the XRD, FESEM, EDX, and UV–Vis, respectively. Next, the best TiO2 multilayer flms with 5 nm Cu were tested for morphological, structural, and optical properties at 600 and 1200 mGy of x-ray radiation. The dosimetric properties of samples irradiated with X-ray doses ranging from 100 to 1500 mGy were then investigated. The best annealing time, reproducibility, fading, low minimum detectable dose as well as the effect of different heating rates on the TL glow curve have all been studied. Our results indicate that the flms are amorphous, porous with spherically shaped nanoparticles, have a uniform distribution of elements, and are transparent in the visible region. The optimum TL intensity was found at TiO 2 (445 nm)/14.2 nm Cu/TiO 2 (130 nm) sequence. The dose-response has a good linear correlation to x-ray radiation with a sensitivity that is 0.444 times less than that of TLD-100 sensitivity within the dose range 100–1500 mGy. Upon irradiation, the band gap decreases, crystallinity increases, pores increase, flms become rougher, and the absorption band edge extends to higher wavelengths. The single and multilayer TiO 2 flms have high-intensity peaks at 270 and 274 ∘ C, respectively, which is typical of TL glow curve peaks used in TLD ap- plications. There were no signifcant changes in the TL reading after six times of reuse, and the fading was observed at 49.57% after 15 days of irradiation. The fndings indicate that TiO 2 /Cu/TiO 2 multilayer flms are appropriate for thermoluminescence dosimetric applications. 1. Introduction Thermoluminescence dosimeter (TLD) is used in a variety of scien- tifc felds, including radiation protection, radiotherapy, industrial, environmental, and space research [1]. TLD is used to estimate absorbed radiation dose [2], and it is useful because it can store radiation that can be read out when needed. There are numerous commercial TLDs that are used in radiation dosimetry. TLD-100 (LiF: Mg, Ti) is a popular TL ma- terial due to its sensitivity, dependability, non-intricateness, portability, and good linear response between delivered doses and measured charge [3,4]. The most commonly used TLDs are made of phosphors, ceramics, and crystals. Despite having a high light output per unit of absorbed dose, they suffer from moisture attack, rapid signal fading, saturation at higher doses, and annealing diffculties for re-use [5]. Furthermore, thin flm materials have received a lot of attention because of their distinct characteristics, which differ signifcantly from their bulk attributes, making them appealing for a variety of applications. Thin flm TL re- sponses are also important for measuring absorbed doses from weakly * Corresponding author. ** Corresponding author. E-mail addresses: as5750327@gmail.com (A.S. Alkadem Idriss), nnashikin@usm.my (N.N.A. Nik Ab Razak). Contents lists available at ScienceDirect Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin https://doi.org/10.1016/j.jlumin.2023.119886 Received 9 January 2023; Received in revised form 15 March 2023; Accepted 18 April 2023