In the present study nickel oxide NiO thin films of thickness ranging about 250-350 nm which were prepared on glass substrates by using chemical spray pyrolysis as a simple and low cost method. The impact of thickness and aqueous solution molarity concentration on the crystal structure and optical characteristics were investigated. The results showed that the deposited films is homogenous and have a good adherent to the glass substrates. The crystal structure results showed that all films have polycrystalline in nature, of rock salt phase, and the preferential orientation is an along (111) plane. The diffraction intensity was increased with the increase in spray solution concentration, leading to the enhancement of the crystallinity and an increase in the crystallite size from 9.7 nm to 28.5 nm and reducing the dislocation density from (104.3 to 12.2) × 1016 line/m2. While the results of AFM results show that the grain size (D) enlarges with increasing molarities concentration. Transmittance spectra confirm that the optical transmittance is of the direct allowed type, while the value of transparency ranged from moderate to weak value and decrease when the spray solution molar concentration and film thickness increases. Whereas the forbidden energy gap was decremented with the increment of molarity concentration of spray solution and film thickness from 3.85 to 3.15 eV.
 Jilani, Asim, Mohamed Shaaban Abdel-Wahab, and Ahmed Hosny Hammad. "Advance deposition techniques for thin film and coating, Modern Technologies for Creating the Thin-film Systems and Coatings , 2, (2017), 137-149.
 Jeun, Jeong-Hoon, and Seong-Hyeon Hong. "Porous SnO2 Films Fabricated by Anodic Oxidation and RIE Process and CuO Additives Effect on Gas Sensing Properties." Nanotechnology, 18 ,(2009):P. 065707.
 Md. Nur Amin Bitu, Nazmul Islam Tanvir, Suravi Islam and Syed Farid Uddin Farhad, Effect of substrate surface on the wide bandgap SnO2 thin films grown by spin coating, MRS Advances volume 8, 194–200 (2023). https://doi.org/10.1557/s43580-023-00515-3.
 A. M. M. Musa; S. F. U. Farhad, M. A. Gafur; and A. T. M. K. Jamil, Effects properties of CuO thin films synthesized by dip-coating for CO2 gas sensing, AIP Advances 11, 115004 (2021). https://doi.org/10.1063/5.0060471.
 Bijoy Chandra Ghos, Syed Farid Uddin Farhad, Md Abdul Majed Patwary, Shanta Majumder, Md. Alauddin Hossain, Nazmul Islam Tanvir, Mohammad Atiqur Rahman, Tooru Tanaka, and Qixin Guo, Influence of the Substrate, Process Conditions, and Postannealing Temperature on the Properties of ZnO Thin Films Grown by the Successive Ionic Layer Adsorption and Reaction Method, ACS Omega 2021, 6, 4, 2665–2674. https://doi.org/10.1021/acsomega.0c04837.
 Meng-Huan Jao, Chien-Chen Cheng, Chun-Fu Lu, Kai-Chi Hsiao and Wei-Fang Su, Low temperature and rapid formation of high quality metal oxide thin film via a hydroxide-assisted energy conservation strategy J. Mater. Chem. C, 2018,6, 9941-9949. https://doi.org/10.1039/C8TC03544J
 S.Palanichamya, J.Raj Mohamedb, K.Deva, Kumarc, P.S.Satheesh Kumara, S.Pandiarajand, L.Amalraj ,"Physical properties of rare earth metal (Gd3+) doped SnO2 thin films prepared by simplified spray pyrolysis technique using nebulizer.", Optik, 194, (2019), 162887.
 Adel H. Omran Alkhayatt and Shymaa K. Hussian Fluorine highly doped nanocrystalline SnO2 thin films prepared by SPD technique, Materials Letters, 155, 2015, 109-113.
 Yousif, Salam Amir, and Jenan Mohamed Abass. "Structural, Morphological and Optical Characterization of SnO2: F thin films prepared by Chemical spray Pyrolysis." International Letters of Chemistry, Physics and Astronomy, 13, (2013): 90-102.
 S. Boulila, M. Ghamnia, A. Boukhachem, A. Ouhaibi, M. A. Chakhoum, C. Fauquet, V. Heresanu & D. Tonneau Photocatalytical properties of NiO nanofilms doped with Ba Phil. Mag. Letters, 110, 6, (2020) 283-293. https://doi.org/10.1080/09500839.2020.1760389.
 A. Angel Ezhilarasi, J. Judith Vijaya, K. Kaviyarasu, L. John Kennedy, R. Jothi Ramalingam, Hamad A. Al-Lohedan, Green synthesis of NiO nanoparticles using Aegle marmelos leaf extract for the evaluation of in-vitro cytotoxicity, antibacterial and photocatalytic properties, Journal of Photochemistry & Photobiology, B: Biology 180 (2018) 39–50.
 Icuk Dian Likasari , Rina Widi Astuti , Amri Yahya , Nur Isnaini , Gani Purwiandono , Habibi Hidayat , Wiyogo Prio Wicaksono , Is Fatimah, NiO nanoparticles synthesized by using Tagetes erecta L leaf extract and their activities for photocatalysis, electrochemical sensing, and antibacterial features, Chemical Physics Letters 780 (2021) 138914.
 Y.ZhO, et al., Structures, electrical and optical properties of nickel oxide films by radio frequency magnetron sputtering. Vacuum 103 (2014): 14-16.
 A. M. Soleimanpour, et al., Surface and gas sensing properties of nanocrystalline NiO thin films. Applied Surface Science 276, (2013):P.p 291-297.
 M.M. Gomaa, M.H. Sayed, V.L. Patil, M. Boshta, and P.S. Patil, Gas sensing performance of sprayed NiO thin films toward NO2 gas, Journal of alloys and compound, 885, 2011, 160908.
 Structural Defect Impact on Changing Optical Response and Raising Unpredicted Ferromagnetic Behaviour in (111) Preferentially Oriented Nanocrystalline NiO Films Crystals, 12(5), (2022)692; https://doi.org/10.3390/cryst12050692.
 M. Guziewicz, et al., Hydrogen sensing properties of thin NiO films deposited by RF sputtering. Procedia Engineering 47 (2012): P.p746-749.
 H. Ivan, L. Jozef, S. Helmut and V. Peter, "properties of sputtered NiO thin films", Journal of Electrical Engineering", Vol. 53, No.11-12, (2002),P.p 339-342.
 D. Y. Jianga, J. M. Qina , X. Wangb, S. Gaoa, A. C. Lianga and J. X. Zhaoa, "Optical properties of NiO thin films fabricated by electron beam evaporation", Vacuum, 86, 8, (2012), 1083-1086.
 C. K. Romana and B. Peter, "Sol-Gel Prepared NiO Thin Films for Electrochromic pplications", Acta Chimica Slovenica, 53, (2006), 136-147.
 Malika Allali, Mohamed Amine Dahamni, Mostefa Ghamnia, Abdelwahab Boukhachem, Djamel Boukrédimi, Didier Tonneau and Carole Fauquet, Synthesis and Investigation of Pure and Cu-Doped NiO Nanofilms for Future Applications in Wastewater Treatment Rejected by Textile Industry Catalysts, 12 (9), (2022) 931; https://doi.org/10.3390/catal12090931.
 J. H. Ahmed, "Study of optical and Electrical Properties of Nickel Oxide (NiO) Thin Films Deposited by Using a Spray Pyrolysis Technique", Journal of Modern Physics, 5, (2014), 2184-2191.
 H. Benzscour, "Synthèse d’un oxyde transparent conducteur (OTC) par pulvérisation chimique (ZnO, NiO)", MSc. Thesis, Badji Mokhtar University, (2008), Algeria.
 B.A. Reguig, M. Regragui, M. Morsli, A. Khelil M. Addou and J.C. Bernede, Effect of the precursor solution concentration on the NiO thin film properties deposited by spray pyrolysis, Solar Energy Materials & Solar Cells 90 (2006) 1381–1392. http://doi.org/10.1016/j.solmat.2005.10.003.
 Hadjer Hakkoum, Toufik Tibermacine, Nouredine Sengouga, Okba Belahssen, Mebrouk Ghougali, Abdelhamid Benhaya, Abderrahim Moumen, and Elisabetta Comini, Effect of the source solution quantity on optical characteristics of ZnO and NiO thin films grown by spray pyrolysis for the design NiO/ZnO photodetectors, Optical Materials, 108, 2020, 110434. https://doi.org/10.1016/j.optmat.2020.110434.
 Amany Fathy, Ahmed B.M. Ibrahim, S. Abd Elkhalik, Alexander Villinger, and S.M. Abbas, Effect of precursor concentration on stoichiometry and optical properties of spray pyrolyzed nanostructured NiO thin film, Heliyon, 9, 2023, e13023. https://doi.org/10.1016/j.heliyon.2023.e13008 .
 Aljarrah, R. M., & Hamza, H. A. (2023, February). Effected of spraying solution concentration on SnO2 films properties for photo-detector application. In AIP Conference Proceedings, 2457, 1, 050011). AIP Publishing LLC.
 R. Pearce, T. Iakimov, M. Andersson, L. Hultman, A. L. Spetz, and R. Yakimova, “Epitaxially grown graphene based gas sensors for ultra sensitive NO2 detection,” Sensors Actuators, B Chem.,155 (2), 2011, 451-4552011.
 G. Williams and G. S. V. Coles, "The Gas-Sensing Potential of Tin Dioxide Produced by a Laser Ablation Technique", MRS Bulletin, 24, 6, (1999), 25-29.
 David C. Look, D. C. Reynolds, C. W. Litton, R. L. Jones, D. B.Eason, and G. Cantwell, "Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy", Applied Physics Letter, 81, 10, (2002), 1830-1832.
 A. M. Reddya, A. S. Reddyb and P. S. Reddya, "Annealing effect on the physical properties of dc reactive magnetron sputtered nickel oxide thin films", Physics Procedia, 49, ( 2013 ), 9-14.
 P.J. Kelly and R.D. Arnell, "Magnetron sputtering: a review of recent developments and applications", Vacuum, 56, (2000), 159-172.
 M. Leskelä, and M. Ritala, "Atomic layer deposition (ALD): from precursors to thin film structures". Thin Solid Films, 409, 1, (2002), 138-146.
 D. Perednis and L. J. Gauckler, "Thin film deposition using spray pyrolysis", Journal of Electroceramics, 14, (2005), 103- 111.
 J. Tauc, " Amorphous and Liquid Semiconductors", Plenum Press,USA, (1974).
 Adel H. Omran Alkhayatt, Structure, surface topography and optical characterization of Ag co – doped Cd1-xCuxO nanostructure thin films, Journal of Kufa – Physics, Vol.9, No.2 (2017), 41-55.
 S. Benramache and B. Benhaoua, “Influence of substrate temperature and Cobalt concentration on structural and optical properties of ZnO thin films prepared by Ultrasonic spray technique,” Superlattices and Microstructures, 52, 4, 807–815, (2012).
 K.O. Ukoba, A.C. Eloka-Eboka, F.L. Inambao, Review of nanostructured NiO thin film deposition using the spray pyrolysis technique, Renew. Sustain. Energy Rev. 82 (2018) 2900–2915.
 T. Chtouki , M. El Mrabet , A. Tarbi . Goncharova , H. Erguig,Comprehensive review of the morphological, linear and nonlinear optical characterization of spin-coated NiO thin films for optoelectronic applications, Optical Materials ,118, (2021).p.111294.
 Muzamil Aftab , M.Z. Butt , Dilawar Ali , Farooq Bashir , Taj Muhammad Khan, Optical and electrical properties of NiO and Cu-doped NiO thin films synthesized by spray pyrolysis, Optical Materials, 119 ,(2021), 111369.
 X. Li, X. Zhang, Z. Li, Y. Qian, Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods, Solid State Commun. 137 (2006), 581–584.
 D. Ali, M.Z. Butt, B. Arif, A.A. Al-Ghamdi, F. Yakuphanoglu, The role of Al, Ba, and Cd dopant elements in tailoring the properties of c-axis oriented ZnO thin films, Phys. B Condens. Matter 506 (2017) 83–93.
 Ratnesh Sharma,, A.D. Acharya, S.B. Shrivastavaa, Manju Mishr Patidarc,Mohan Gangrade, T. Shripathi, V. Ganesan, Studies on the structure optical and electrical propertiesof Zn-doped NiO thin films grown by spray pyrolysis, Optik ,127, (2016), 4661–4668.
 S. Sharma, C. Periasamy, P. Chakrabarti, Thickness dependent study of RF sputtered ZnO thin films for optoelectronic device applications, Electron. Mater. Lett. 11 (6) (2015), 1093–1101.
 J. D. Desai, S.-K.Min, K.-D. Jung, andO.-S. Joo, “Spray pyrolytic synthesis of large area NiOx thin films from aqueous nickel acetate solutions,” Applied Surface Science, 253, 4, 1781–1786, 2006.
 H. A. Juybari, M.-M. Bagheri-Mohagheghi, and M. Shokooh- Saremi, “Nickel-lithium oxide alloy transparent conducting films deposited by spray pyrolysis technique,” Journal of Alloys and Compounds, 509, 6, 2770–2775, (2011).
Aljarrah, Radhiyah M.; Naamah, Ali Madlool; and Alkhayatt, Adel H. Omran
"Concentration of Spraying Solution Effect on the Structural, Morphological and Optical Properties of NiO Thin Films,"
Al-Bahir Journal for Engineering and Pure Sciences: Vol. 3
, Article 4.
Available at: https://doi.org/10.55810/2312-5721.1039